lucrari revista_ti 2-3-2009

REVISTA CONSTRUCŢIA DE MAŞINI

Anul 61, Nr. 2 - 3/ 2009

Din sumar

TEHNOLOGII INOVATIVE INNOVATIVE TECHNOLOGIES

MODELARE & SIMULARE MODELLING & SIMULATION

RESURSE UMANE & INOVARE HUMAN RESOURCES & INNOVATION

ISSN 0573 – 7419 EDITOR: ICTCM – CITAf - OID.ICM 041303 Bucuresti Şos. Olteniţei nr. 103, sector 4, O.P. 8 Tel: 021 332.37.70/234 Fax: 021 332.07.75 / 021 332.31.95 E-mail: [email protected]

Responsabil editor: Irina Rădulescu Responsabil difuzare: Ionuţ Dimache INFORMAŢII, ABONAMENTE: Revista este evaluată CNCSIS la categoria B+, apare trimestrial. Abonamentele se fac direct, prin dispoziţie de plată sau mandat poştal, trimis pe adresa revistei. CONT – ICTCM: nr. RO58 RNCB 0075 0352 1240 0001; BCR sector 4 TIPAR: OID.ICM COPYRIGHT 2003 Toate drepturile asupra acestei ediţii sunt rezervate OID.ICM. Nu este permisă reproducerea integrală sau parţială a articolelor din revista „Tehnologia Inovativă” fără consimţământul scris al editorului. Opiniile exprimate în revistă aparţin semnatarilor articolelor, fără să reflecte obligatoriu şi punctul de vedere al editorului.

TEHNOLOGIA INOVATIVĂ – Revista „Construcţia de maşini” nr. 2 - 3 / 2009

ANUL 61 / 2009 – NR. 2 - 3

TEHNOLOGIA INOVATIVĂ


COLEGIUL DE REDACŢIE Octavian BOLOGA - Universitatea „Lucian Blaga” din Sibiu

Olivier BONNEAU – Universitatea din Poitiers, Franţa

Ion BOSTAN – Universitatea Tehnică a Moldovei

K.D. BOUZAKIS – Aristoteles University of Thessaloniki, Grecia

Doug BRANHAM - Lubrication Systems Company, Houston, Texas, USA

Dan BRÎNDAŞU - Universitatea „Lucian Blaga” din Sibiu

Mircea CIOBANU - Universitatea „Ştefan cel Mare” din Suceava

Valeriu DULGHERU – Universitatea Tehnică a Moldovei

Dan FILIPOIU - Universitatea POLITEHNICA din Bucureşti

Michel FILLON – Universitatea din Poitiers, Franţa

Mohamed HAJJAM – Universitatea din Poitiers, Franţa

Tudor ICLĂNZAN - Universitatea „Politehnica” din Timişoara

Nicolae Valentin IVAN - Universitatea „TRANSILVANIA” din Braşov

Gheorghe MOGAN – Universitatea „TRANSILVANIA” din Braşov

Ilie MUSCĂ - Universitatea „Ştefan cel Mare” din Suceava

Nicolae OANCEA - Universitatea „Dunărea de Jos” din Galaţi

Dumitru OLARU - Universitatea Tehnică „Gheorghe Asachi” din Iaşi

Juozas PADGURSKAS – Lithuanian University of Agriculture, Lithuania

Radu POPESCU – Academia Română - INCE – CEIS, Bucureşti

Tudor PRISĂCARU - Universitatea POLITEHNICA din Bucureşti

Vasile PUIU - Universitatea din Bacău

Stanisław PYTKO - University of Science and Technology, Kraków, Poland

Alexandru RĂDULESCU - Universitatea POLITEHNICA din Bucureşti

Minodora RÎPĂ - Universitatea „Dunărea de Jos” din Galaţi

Lucian TUDOSE - Universitatea din Cluj

Thami ZEGHLOUL – Universitatea din Poitiers, Franţa


COMITET ONORIFIC

Gheorghe AMZA - Universitatea POLITEHNICA din Bucureşti

Niculae Napoleon ANTONESCU – Universitatea „Petrol şi Gaze” din Ploieşti

Traian AURITE - Universitatea POLITEHNICA din Bucureşti

Gavrilă CALEFARIU - Universitatea „TRANSILVANIA” din Braşov

Mircea COZMÎNCĂ - Universitatea Tehnică „Gheorghe Asachi” din Iaşi

Emanuel DIACONESCU – Universitatea „Ştefan cel Mare” din Suceava

Marian GHEORGHE - Universitatea POLITEHNICA din Bucureşti

Constantin ISPAS - Universitatea POLITEHNICA din Bucureşti

Valeriu JINESCU - Universitatea POLITEHNICA din Bucureşti

Aurel JULA - Universitatea „TRANSILVANIA” din Braşov

Constantin MINCIU - Universitatea POLITEHNICA din Bucureşti

Eugen PAY - Universitatea de Nord din Baia Mare

Iulian POPESCU - Universitatea din Craiova

Aurelian VLASE - Universitatea POLITEHNICA din Bucureşti

Ioan VOICA - Universitatea POLITEHNICA din Bucureşti

EDITOR

Oficiul de Informare Documentară pentru Industrie, Cercetare, Management din cadrul

Centrului Incubator Tehnologic de Afaceri S.C. ICTCM S.A. BUCUREŞTI

RESPONSABIL EDITOR

Irina Rădulescu

REDACTOR Irina Rădulescu


CUPRINS

TEHNOLOGII INOVATIVE / INNOVATIVE TECHNOLOGIES

1. STUDY CASE - TAMPING TOOLS WITH THE REINFORCEMENT BY TUNGSTEN CARBIDE AT THE TINE pag. 5

C. Beşleagă1, I.C. Popescu2, R.M. Negriu3, S.G. Badea1 1 SC IMCF SA, Bucharest, ROMANIA 2 Polytechnic University, Bucharest, ROMANIA 3 SC Econet Prod SRL, Bucharest, ROMANIA

2. INTELLIGENT MECHATRONIC EQUIPMENT FOR VECTORIAL MASO – KINETOTHERAPY pag. 11 T. S. Crăciunoiu1, V. Avramescu2, I. Stoian3, C. Dumitru4, C. H. Orăşanu5, R. Grejdănescu6, L. T. Păun7 , T. M. Muntenu8, O. Surdu9, V. Mihăilescu10

1, 2, 3, 4, 5, 6, 7SC ICTCM - Mechanical Engineering and Research Institute SA, Bucharest, ROMANIA 8SC Mecanica Ceahlau Piatra Neamt, Piatra Neamţ, ROMANIA, 9Balnear Sanatorium and Recovery Techirghiol, Constanta, ROMANIA, 10Professor Constantin Popovici Foundation, Bucharest ROMANIA

3. MULTIFUNCTIONAL SURGICAL TABLE pag. 15 T. S. Crăciunoiu1, V. Avramescu2, A. V. Ciurea3, C.M. Birtu4, A.M. Croitoru5, V.T. Grigorean6, I. Lung7, R.S. Crăciunoiu8, L.T. Păun9, R. Grejdănescu10

1, 2,4,5,8,9,10 SC ICTCM - Mechanical Engineering and Research Institute SA Bucharest, ROMANIA 3 Bagdasar-Arseni Clinic Emergency Hospital, Bucharest, ROMANIA, 7 The National Institute of R-D in Mechatronichs and Measurement Technique INCDMTM, Bucharest, ROMANIA

4. SYSTEM FOR DATA AQUISITION AND ANALYSIS OF THE KINEMATICS OF THE GAIT FOR THE COMAND OF A ROBOTIZED ORTHOTIC SUIT pag. 21 F. Alexiuc1, V. Avramescu2, G. Onose3, L.T. Păun4, R. M. Niţă5, C.H. Orăşanu6, R. Grejdănescu7, C. N. Nicolau8, A. M. Croitoru9, R. S. Crăciunoiu10

1, 2, 4, 5, 6, 7, 8, 9, 10 SC ICTCM - Mechanical Engineering And Research Institute SA, Bucharest, ROMANIA 3 Bagdasar-Arseni Clinic Emergency Hospital, Bucharest, ROMANIA

5. INTEGRATED CONCEPTUAL MODEL OF A WHEELCHAIR, MADE BY THE DEVELOPMENT OF SOME COMPONENTS THAT ARE PART OF ITS STRUCTURE pag. 25

Grigore Stanca1, C.Dumitru2, C.H. Orăşanu3, V. Avramescu4, G. Onose5 , L. Păun6 , R. Grejdănescu7 , R.M. Niţă8 , R.S. Crăciunoiu9 , I. Dimache10 1,2,3,4,6,7,8,9,10SC ICTCM - Mechanical Engineering and Research Institute SA,Bucharest, ROMANIA 5 Bagdasar-Arseni Clinic Emergency Hospital, Bucharest, ROMANIA

6. METODE MODERNE DE STUDIU A NANOCOMPOZITELOR pag. 29 Carmen Răducanu, Gabriela Diacov, Dumitru Bucă, Roxana Neagu, Mihaela Hrişcu SC ICTCM Institutul de Cercetare şi Proiectare Tehnologică pentru Construcţia de Maşini SA Bucureşti, ROMANIA MODELARE & SIMULARE / MODELLING & SIMULATION

7. THEORETICAL CONSIDERATION REGARDING THE DYNAMIC BEHAVIOUR OF A MODULAR SYSTEM FOR THE MILLING PROCESS pag. 37 Raluca Magdalena Niţă1, Nicoleta Rachieru2 1University Politechnica of Bucharest, SC ICTCM SA, Bucureşti, ROMANIA 2 SC ALPLAST CONF SRL, ROMANIA


8. STUDY OF A EHD POCKET JOURNAL BEARING pag. 43 Monica Crudu *, Sorin Cănănău*, Mohamad Hajjam**

*University “POLITEHNICA” Bucharest, ROMANIA, ** Solid Mechanics Laboratory of Poitiers University, FRANCE

9. STUDY OF A HD POCKET JOURNAL BEARING pag. 47 Monica Crudu*, Sorin Cănănău*, Aurelian Fătu** *University “POLITEHNICA” Bucharest, ROMANIA, ** Solid Mechanics Laboratory of Poitiers University, FRANCE

10. SLIP/NO-SLIP INFLUENCE ON THE BEHAVIOR OF A RADIAL BEARING WITH A STATIC LOAD. HD ANALYZES pag. 51 Daniela Coblaş *, Aurelian Fătu**, Alexandru Rădulescu*

* University of Polytechnics, Bucharest, ROMANIA, ** Solid Mechanics Laboratory of Poitiers University, FRANCE

11. SLIP/NO-SLIP INFLUENCE ON THE BEHAVIOR OF A RADIAL BEARING WITH A STATIC LOAD. EHD ANALYZES pag. 55 Daniela Coblaş *, Mohamed Hajjam**, Alexandru Rădulescu*

* University of Polytechnics, Bucharest, ROMANIA, ** Solid Mechanics Laboratory of Poitiers University, FRANCE

12. THEORETICAL RESEARCHES REGARDING THE STATIC BEHAVIOUR OF A TRANSVERSAL SLIDE FOR MULTIFUNCTIONAL MACHINE TOOLS pag. 59 Raluca Magdalena Niţă, Loredana Păun, Roxana Grejdănescu SC ICTCM SA, Bucharest, ROMANIA

13. RECHERCHES EXPERIMENTALES SUR LE COMPORTEMENT THERMIQUE DES LUBRIFIANTS USES pag. 65 Alexandru V. Rădulescu1, Irina Rădulescu2 1 Université POLITEHNICA de Bucarest, Bucarest, 2 S.C. I.C.T.C.M. S.A.Bucarest, ROUMANIE

14. ASPECTE PRIVIND PROIECTAREA OPTIMIZATĂ A ELEMENTULUI DE STRUCTURĂ TIP BRAŢ ARTICULAT AL UNUI ROBOT RRR pag. 71 Adrian Ghiorghe Politehnica University of Bucharest, ROMANIA RESURSE UMANE & INOVARE / HUMAN RESOURCES & INNOVATION

15. INOVAREA ÎN CADRUL SISTEMELOR COMPLEXE DE PRODUCŢIE pag. 77 Radu Popescu INCE - CEIS, Bucureşti, ROMANIA

16. SPRIJINIREA PE LEGĂTURILE EXTERNE ÎN PROMOVAREA INOVĂRII pag. 81 Radu Popescu

INCE - CEIS, Bucureşti, ROMANIA 17. CLASICII REALIZĂRII EXCELENŢEI pag. 85

Radu Popescu *, Emilia Stănescu**

* INCE - CEIS, ** INIMM, Bucureşti, ROMANIA 18. EXCELENŢA ŞI DURABILITATEA INTREPRINDERILOR pag. 89

Radu Popescu *, Rareş Dima**

* INCE - CEIS, ** INIMM, Bucureşti, ROMANIA


ABSTRACTS “INNOVATIVE TECHNOLOGY” 2 - 3 / 2009

STUDY CASE - TAMPING TOOLS WITH THE REINFORCEMENT

BY TUNGSTEN CARBIDE AT THE TINE

C. Besleaga1, I.C. Popescu2, R.M. Negriu3, S.G. Badea1

1 SC IMCF SA, Bucharest, ROMANIA,

[email protected] 2 Polytechnic University, Bucharest, ROMANIA

3 SC Econet Prod SRL, Bucharest, ROMANIA

An important operation in the technical process of building or maintenance of the railways is tamping. Tamping operation is made by different tamping machines, using tamping tools. Tamping tools are the most stress part of the tamping machine, being stress at bending, oscillations, abrasive wear, s.a. The main part of a tamping tool which influences in present the lastingness of this is the active part (tine). The research team proposes a study cases using CAD, a new composite material, with tungsten carbide, for the tine and there were made researches regarding the behavior in situ for the different tamping tools.

INTELLIGENT MECHATRONIC EQUIPMENT FOR VECTORIAL MASO - KINETOTHERAPY

T. S. Craciunoiu1, V. Avramescu2, I. Stoian3,

C. Dumitru4, C. H. Orasanu5, R. Grejdanescu6, L. T. Paun7 , T. M. Muntenu8, O. Surdu9,

V. Mihailescu10

1, 2, 3, 4, 5, 6, 7SC ICTCM - Mechanical Engineering and

Research Institute SA, Bucharest, Romania [email protected], [email protected],

[email protected], [email protected] 8SC Mecanica Ceahlau Piatra Neamt, Piatra Neamţ,

Romania, [email protected] 9Balnear Sanatorium and Recovery Techirghiol, Constanta, Romania, [email protected]

10Professor Constantin Popovici Foundation, Bucharest, Romania, [email protected]

The recovery proces of elderly or disabled person is a major problem with implications on the social environment and on the medical environment due to the complexity of treatment, its duration, standard equipment and specialized capable equipment. Intelligent mechatronic equipment for monitoring patients, persons with disabilities and the elderly have become an immediate necessity, the world providing a

wide range of such systems, from simple to complex. Each person (more or less, sooner or later) needs to treat post recuperator, the mechatronics equipment (assisted adjustable bed) proposed to achieve through its multimunctionalit, is necessary, particularly in recovery sanatoriums (regardless of the conditions of patients) and in hospitals for postoperative situations. Important is that these mechatronic equipment with medical applications have integrated sensors and systems which gives them the special multifunctionalitaty and intelligence.

MULTIFUNCTIONAL SURGICAL TABLE

T. S. Crăciunoiu1, V. Avramescu2, A. V. Ciurea3, C.M. Birtu4, A.M. Croitoru5, V.T. Grigorean6, I.

Lung7, R.S. Crăciunoiu8, L.T. Păun9, R. Grejdănescu10

1, 2,4,5,8,9,10 SC ICTCM - Mechanical Engineering and

Research Institute SA Bucharest, Romania e-mail: [email protected], [email protected], [email protected], [email protected],

[email protected], [email protected] 3 Bagdasar-Arseni Clinic Emergency Hospital,

Bucharest, Romania, [email protected] 7 The National Institute of R-D in Mechatronichs and

Measurement Technique – INCDMTM, [email protected] One of the surgical system priorities is the need to ensure the patient safety and creating the optimal conditions of the operator, for example: the need to adopt some various positions of the patient or the need to change the intraoperator position of the patient. There are better surgical tables, made by several segments that can be operated independently. Also is developing a wide range of intelligent devices and accessories to allow expansion of the medical act, ensuring precision, maneuverability, accuracy, patient safety, patient and operator comfort. A particular case is the development of mechatronic equipment in medical applications, such as mechatronic systems for vectorial maso- kinetotherapy recovery treatments. The importance of this is that these mechatronic devices with medical applications have integrated sensors and special systems which gives them the multifunctionality and intelligence.


SYSTEM FOR DATA AQUISITION AND ANALYSIS OF THE KINEMATICS

OF THE GAIT FOR THE COMAND OF A ROBOTIZED ORTHOTIC SUIT

F. Alexiuc1, V. Avramescu2, G. Onose3, L.T. Paun4,

R. M. Nita5, C.H. Orasanu6, R. Grejdanescu7, C. N. Nicolau8, A. M. Croitoru9, R. S. Craciunoiu10

1, 2, 4, 5, 6, 7, 8, 9, 10 SC ICTCM - Mechanical Engineering And Research Institute SA, Bucharest, Romania

[email protected], [email protected], [email protected], [email protected], [email protected],

[email protected], [email protected], [email protected], [email protected]

3 Bagdasar-Arseni Clinic Emergency Hospital, Bucharest, Romania, [email protected] The researches which were made in the project “Informatics system based on data acquisition and advanced decision in real time methods for the command and control of an robotized orthotic suit in order to assist the persons with locomotors disabilities”, follow the achievement of a software for the data acquisition, in real time, and also the decisions making for keeping the orthostatism and the equilibrium. The project was developed by a consortium formed by SC ICTCM SA, Bagdasar-Arseni Clinic Emergency Hospital, UPB-CTANM, SC Neuron SRL and Tehnicom 3D-ING SRL. In the first stage of the project there were achieved the data related to motion: the acquisition of the analogical signals provided by the potentiometers displaced in the robotized orthotic suit’s joints and the acquisition of the signals provided by the pressure sensors displaced on the base of the foot. The data acquisition system can be used in the kinetotheraphy clinics in order to evaluate and medical recovery of the patients. In the second stage there is considered the simulation of the behaviour of the robotized orthotic suit in the virtual medium in order to study the behaviour of the orthotic suit and of the human subject in order to find the hardware and software elements which should assure the safety development of the ascension/descent movements, orthostatism, gait and equilibrium, reaction to the perturbing factors, etc.

INTEGRATED CONCEPTUAL MODEL OF A WHEELCHAIR, MADE BY

THE DEVELOPMENT OF SOME COMPONENTS THAT ARE PART OF ITS STRUCTURE

Grigore Stanca1, C.Dumitru2, C.H. Orasanu3, V.

Avramescu4, G. Onose5 , L. Paun6 , R. Grejdanescu7 , R.M. Nita8 , R.S. Craciunoiu9 , I. Dimache10

1,2,3,4,6,7,8,9,10SC ICTCM - Mechanical Engineering and

Research Institute SA,Bucharest, Romania [email protected], [email protected],

[email protected], [email protected], [email protected], [email protected], [email protected]

5 Bagdasar-Arseni Clinic Emergency Hospital, Bucharest, Romania, [email protected]

The researches made in this project had as main objective the conceptual development of some integrated, complex, competitive models of complex equipments which to carry out the problems of the persons with a high degree of disabilitation for reducing their psychological impact and for their socio-economic integration, in general by offering them a means of independent transportation and the realization of the experimental models of some wheel chairs, that are hand power or electric power, with modular and flexible structures, with a high degree of flexibility. Based on the conceptual models can be developed in the future a wide range of similar equipments, with simple or complex functions, hand power or driven by other means, fix, foldable, with special accessories, with flexibility possibilities according to the disabilitation degree, for offering safety to the persons with neuro-kinetic deficiencies.

MODERN METHODS FOR THE STUDY OF NANOCOMPOSITES

Carmen Răducanu, Gabriela Diacov, Dumitru Bucă,

Roxana Neagu, Mihaela Hrişcu

SC ICTCM Institutul de Cercetare si Proiectare Tehnologica pentru Constructia de Masini SA

Bucuresti, ROMANIA E-mail: [email protected]

The paper offers the most recent information on high resolution microscopic systems. There have been studied several methods concerning the visualization of the structure of electrodeposisits nanocomposites: TEM (Transmision Electron Microscope), SEM (Scanning Electron Microscope), AFM- (Atomic Force Microscope), STM (Scanning Tunelling Microscope). Toghether with basic technical data, the paper also presents typical images for the involved studying methods.


THEORETICAL CONSIDERATION REGARDING THE DYNAMIC BEHAVIOUR

OF A MODULAR SYSTEM FOR THE MILLING PROCESS

Raluca Magdalena Nita1, Nicoleta Rachieru2

1University Politechnica of Bucharest, SC ICTCM SA,

e-mail [email protected] 2 SC ALPLAST CONF SRL, e-mail [email protected]

The papers aims to study with the finite elements method the dinamic behaviour of a modular system for clamping the pieces during the cutting process, through the determination of the characteristic frequency where performance, reliability, durability and reliability in function represents the fundamental characteristics have great influence on the final results of processing process.

STUDY OF A EHD POCKET JOURNAL BEARING

Monica Crudu *, Sorin Cananau**,

Mohamad Hajjam***

*University “POLITEHNICA” Bucharest, ROMANIA,

e-mail: [email protected] **University “POLITEHNICA” Bucharest, ROMANIA, e-mail: [email protected]

*** Solid Mechanics Laboratory of Poitiers University, FRANCE

This paper deals with the textured surfaces effects of a journal bearing working in elastohydrodynamic regime. The fact that texture surfaces increase the carrying capacity and decrease the friction losses in the applications concerning the bearings, mechanical face seals and piston-cylinder couple, it’s already known. In the elastohydrodynamic lubrication regime the increase of the maximal pressure and film thickness is more accentuate that in the hydrodynamic regime because we take into account the elastic behavior of the materials. The main goal of this study is to determine the optimal pocket texture geometry, which gives the largest carrying capacity and the smallest power dissipation by geometrical modeling.

STUDY OF A HD POCKET JOURNAL BEARING

Monica Crudu*,Sorin Cănănău**, Aurelian Fătu***

*University “POLITEHNICA” Bucharest, ROMANIA,

e-mail: [email protected] **University “POLITEHNICA” Bucharest,

ROMANIA, e-mail: [email protected] *** Solid Mechanics Laboratory of Poitiers University,

FRANCE

More and more studies have revealed an increase of the carrying capacity and a decrease of friction losses due to the positive effects of surface texturing concerning the field of bearings, mechanical face seals and piston-cylinder couple. Also it is well known that pocket texture amplifies this effect for hydrodynamic journal bearing more than partial texture [1]. Based on this hypothesis, this paper represents a first step in studying the texturing effects on hydrodynamic journal bearing by assessing the performances of a pocket journal bearing. The main asset of this study is to determine the optimal geometry, which gives the largest carrying capacity zone and the smallest power dissipation by geometrical modeling the three dimensions of the pocket: width, circumferential length and depth of the pocket. SLIP/NO-SLIP INFLUENCE ON THE BEHAVIOR

OF A RADIAL BEARING WITH A STATIC LOAD. HD ANALYZES

Daniela Coblaş *, Aurelian Fătu**,

Alexandru Rădulescu***

* University of Polytechnics, Bucharest, ROMANIA,

e-mail: [email protected] ** Solid Mechanics Laboratory of Poitiers University,

FRANCE, e-mail: [email protected] *** University of Polytechnics, Bucharest, ROMANIA,

e-mail: [email protected]

This paper aims to examine the influence of wall slip on HD lubrication performance of a journal bearing. The study follows two main directions: first to increase fluid film thickness to obtain a greater load capacity and second to reduce power loss. By numerical modelling, we had modified the geometric parameters of a slip surface placed on the sleeve bearing. Results show that for a well chosen surface geometry it is possible to improve the bearing performances.


SLIP/NO-SLIP INFLUENCE ON THE BEHAVIOR OF A RADIAL BEARING WITH A STATIC

LOAD. EHD ANALYZES

Daniela Coblaş *, Mohamed Hajjam**, Alexandru Rădulescu***

* University of Polytechnics, Bucharest, ROMANIA,

e-mail: [email protected] ** Solid Mechanics Laboratory of Poitiers University, FRANCE, e-mail: [email protected]

*** University of Polytechnics, Bucharest, ROMANIA, e-mail: [email protected]

In this paper we present a study on the behavior of a steady-state radial bearing assuming the existence of slip phenomenon at the fluid-solid interface with the sleeve bearing wall. The bearing operates in elasto-hydordynamic lubrication regime, disconsidering thermal influence, and taking into account the general assumptions considered for determining Navier-Stokes equation for the general hydrodynamic lubrication case. Like presented in the previous article, the computation was possible by using numerical modeling software Accel, available thanks to LMS Laboratory, belonging to Poitiers University. Only by using this software, the available time we had was sufficient to perform this study.

THEORETICAL RESEARCHES REGARDING THE STATIC BEHAVIOUR OF A

TRANSVERSAL SLIDE FOR MULTIFUNCTIONAL MACHINE TOOLS

Raluca Magdalena Nita, Loredana Paun,

Roxana Grejdanescu

SC ICTCM SA, Bucharest, ROMANIA, e-mail [email protected]

The paper aims to study with the finite elements method the static behavior of transversal slide, component of a multifunctional machine tool, under the function during processing, in the conditions of steel and a composite slide. It’s very important to determine the performance, resistance and security in functioning because this represent fundamental characteristics on the final results of the processing process.

EXPERIMENTAL RESEARCHES ON THE THERMAL BEHAVIOR

OF USED LUBRICANTS

Alexandru V. Rădulescu1, Irina Rădulescu2

1 Université POLITEHNICA de Bucarest, Bucarest, ROUMANIE, e-mail : [email protected]

2 S.C. I.C.T.C.M. S.A. Institut de Recherches Technologiques pour la Construction des Machines,

Bucarest, Roumanie, e-mail : [email protected]

This article proposes to study the thermal behavior of fresh and used lubricants, taking account to the variation of viscosity versus temperature. The proposed rheological model for fresh and used lubricants is the Newton model, where the shearing stresses in the fluid are proportional to the velocity gradient. Information on the viscosity of lubricants can be regarded as a "window" to analyze other fluids properties. The viscosity is always easier to measure than many other properties of lubricants, providing a very important tool for the fluids characterization.

ASPECTS CONCERNING THE OPTIMIZED DESIGN

OF AN ARTICULATED ARM TYPE STRUCTURAL ELEMENT OF A RRR ROBOT

Adrian Ghiorghe

Politehnica University of Bucharest,

ROMANIA,Faculty of Engineering and Management of Technological Systems

e-mail : [email protected]

Optimization of structural elements of industrial robots is essential in modern design optimized by finite element simulation and obtain a modification of the structure with maximum rigidity. By applying structural and topology optimization algorithm was intended to determine optimal values for design variables in terms of reducing material in the structure of the robot. Structural optimization is to achieve MEF parameterized geometrical model of the assembly robot, by considering some geometric sizes as design variables, imposing restrictive conditions on the model and establish an objective function to optimize. The runs of the FEM analysis, are different values of design variables and state variables are processed, to determine the feasibility set of design variables in order to determine an optimal set (minimum) in terms of objective function.


INNOVATION IN THE COMPLEX PRODUCTION SYSTEMS

Radu Popescu

INCE - CEIS, ROMANIA,

[email protected] The paper analyses the proces of inovation in the field of Product Complex Systems (PCS).These systems have a high content of knowledge and an important place in the Knowledge Economy. Interaction between product and process inovation has similarities with the interaction between mechanical parts and that of firm architecture.

SUPPORTING ON EXTERNAL LINKS TO PROMOTE INNOVATION

Radu Popescu

INCE - CEIS, ROMANIA,

[email protected]

External results assesment is a necesity requested, by the speed of technological changes. Companies have to balance between two options: To maintain the necessary competencies in order to build Product Complex Systems and to prevent the lack of concentration and specialisation when the technological model changes.

CLASSICS FOR THE EXCELLENCE ACHIEVING


* INCE - CEIS, ROMANIA, [email protected]

** INIMM, Bucureşti, ROMANIA, e-mail: [email protected]

The behaviour of excellent firms, companies able to obtain important achievements is characterised by inconventional activities (details separate the average firms of the excellent ones). Amoungh them we can observe: to meet the clients needs, involvement of highly qualified specialists, enthusiasms firms activities, high level quality assurance.

EXCELLENCE AND SUSTAINABILITY

OF ENTERPRISES




The evolution of global thinking in business, especially strategic thinking on company business, company or industrial firms, is a gradual sedimentation process of accumulated knowledge. The main objective of the company's concern is improving the situation at the time of the analysis and achievement of excellence in the future.


5

STUDY CASE - TAMPING TOOLS WITH THE REINFORCEMENT

BY TUNGSTEN CARBIDE AT THE TINE

C. Besleaga1, I.C. Popescu2, R.M. Negriu3, S.G. Badea1

1 SC IMCF SA, Bucharest, ROMANIA, [email protected] 2 Polytechnic University, Bucharest, ROMANIA 3 SC Econet Prod SRL, Bucharest, ROMANIA

REZUMAT O operatie importanta in procesul tehnologic de constructie sau intretinere a caii ferate este burajul. Operatia de burare este facuta de diferite masini de burat, utilizand scule de burare. Sculele de burare sunt cele mai solicitate parti ale masinii de burat, fiind solicitate la incovoiere, vibratii, uzare abraziva etc. Principala parte a unei scule de burare care influenteaza in prezent durabilitatea acesteia este partea active (tachetul). Echipa de cercetatori propune un studiu de caz utilizand CAD, un nou material compozit, cu carburi de wolfram, pentru tachet si realizând cercetari privind comportarea “in situ” pentru diferite scule de burare.

ABSTRACT An important operation in the technical process of building or maintenance of the railways is tamping. Tamping operation is made by different tamping machines, using tamping tools. Tamping tools are the most stress part of the tamping machine, being stress at bending, oscillations, abrasive wear, s.a. The main part of a tamping tool which influences in present the lastingness of this is the active part (tine). The research team proposes a study cases using CAD, a new composite material, with tungsten carbide, for the tine and there were made researches regarding the behavior in situ for the different tamping tools.

KEYWORDS: tamping tools, composite material, tungsten carbide, CAD, weariness CUVINTE CHEIE: scule de burare, material compozit, carburi de wolfram, CAD, uzura

1. INTRODUCTION

The researches regarding to increasing of tamping tools

have been made on the three main directions: Theoretical researches regarding to situations’ stress of a tamping tool, having in view the system’ stress (forces) and the CAD analyzing;

Theoretical and experimental researches regarding to establishing of some new material’ composition for tamping tine and also, of technological processes by made of this;

Experimental researches (in situ), regarding to the behavior of different tamping tools.

2. STUDY CASE - TAMPING TOOL TYPE BNRI - 85 MODELS 94

For to theoretical study case of the tamping tool BNRI- 85, model 94 (Fig.1), was used two CAD soft (Autodesk Inventor Professional 2008 and ANSYS Workbench, rev. 11), in collaboration with the Thermal Research Center, in the Faculty of Mechanical Engineering and Mechatronics of the Polytechnic University in Bucharest [1, 2]. There are used more then 2000000 elements and 3% convergence.


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Fig.1: The Model of tamping tool BNRI – 85 types, model 94 For this model were made 6 cases of stress, two from them are presented below. 2.1. Case 3- Checking/ behavior of the tamping tool BNRI- 85, model 94, at case 3 of stress - Concentrated force, perpendicular to the lower side (active edge) of the tine, operating in the center of the area (Fig.2 ÷ Fig.7).

Fig.2: Scheme of stress

Fig.3: Equivalent stresses (tensions)

Fig.4: Stress (tension) intensity

Fig.5: Life

Fig.6: Total Deformation

Fig.7: Defects (damages)


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2.2. Case 5- Checking/ behavior of the tamping tool BNRI- 85, model 94, at case 5 of stress - Concentrated force, perpendicular to the active main side of the tine, operating in the center of the area (Fig. 8 ÷ Fig.13).

Fig. 8: Scheme of stress

Fig.9: Equivalent stresses (tensions)

Fig.10: Stress (tension) intensity

Fig.11: Life


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Fig.12: Total Deformation

Fig.13: Defects (damages)

3. NEW COMPOSITE MATERIAL WITH METALLIC CARBIDES

For the main piece of wear (tine), we have proposed and

achieved a new technological process of casting at the check’ parameters of a steel, with an original composition, having the role of joint material of the waste from metallic carbide (the waste from metallic carbides are coming from the damage cutting tools, for metal, wood and s.a.). The original composite material which has been achieved is made from particles of metallic carbides, with a certain granulometry (size), incorporation through diffusion into metallic matrix. The matrix of the composite material is heating over the melting point of the binding material from waste composition of sintered metallic carbides (WC-Co, WC-Ni, WC-Co-Ni and TiC-X) and it is casting into relative cold form (shape). The binding metal (Co-Ni) is dissolved and diffusion into metallic matrix and after that it is solidifies. We have achieved a composite material, which is able to satisfied the hard wear conditions, at the local abrasive wear stress, vibrations, having a hardness bigger than the limit’ conditions impose by the crushed stone’ abrasiveness [3, 4, 5, 6, 7].

Fig.14. Micro dilution of carbides particles (Carbides - Detail x 12000)

The main types of analyzed’ particles are titan carbides (TiC) and tungsten carbides (WC). The infiltrations’ analyze with particles from metallic carbides has showed the fact that the TiC has a finest particles’ shape, with relative round shape, which confer a good plasticity of the reinforced matrix, while the WC has a rough morphology, with sharp’ edge and corner, conferring resistance and hardness. The combination of both effects has a good results, by point of view of the behavior in function, if are resolved the problems regarding to the fragility’ and fissure’ tendency of the composite metallic material. The phenomenon which occur at the interface between metallic matrix and carbide’ particle are depending in a big measure by the size, chemistry and physics’ characteristics of these, and also, by the manufacturing.

4. EXPERIMENTAL PROCEDURE

We have established an experimental procedure [8], for evaluated the lastingness of a tamping tool. The lastingness of a tamping tool is the period of time, in which the tamping tool work in the established parameters (until to reaching the limits of wear of an active part- the tine), until to a new regeneration (Fig. 15). The lastingness of a tamping tool can be evaluated through meters (kilometers) of tamping, hours of tamping or, number of insertion. Because the evaluation of lastingness in meters (kilometers) can be use more easily, we have adopted this unit. For the limits of the wear of tine, having in view indications [8] and our experience, we have adopted the following size of wear: 15 mm on side; 20 mm at the corner (40 mm on diagonals).

Fig.15. The limits of the wear for active part (tine)

of a tamping tool

Ui = h – hi; i= 1 ÷ 6; Umed = (U1+ U2+....+ U6): 6


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5. RESEARCHES IN SITU ON THE DIFFERENT LOTS OF THE TAMPING TOOLS

After the researches, regarding to established which is

the main tamping tool (having in view the quantity, consumption criteria) which is use in present, from all types of tamping tools which are used, the researches in situ have been concentrated on the tamping tool BNRI- 85, model 94, followed that the conclusions of these researches to be extended to all types of the tamping tools. 5.1. Experimental researches in situ on the lot 1

of the tamping tools

The experimental researches (in situ) have been made with BNRI- 85 tamping machines, on three tamping tools type BNRI-85, model 94, identified with G4, G6 and G8(7), with the tine which have been made on the base of a new composite material, with tungsten carbide (Fig.16, 17, 18). The behavior of these tools, taking in account the weariness [mm] depending by [km] of tamping is present in Fig. 19.

Fig.16. Tamping tool G4

Fig.17. Tamping tool G6

Fig.18. Tamping tool G8 (7)

5.2. Experimental researches in situ on the lot 2 of the tamping tools

For comparison, we have established another lot,

number 2, with 8 tamping tools type BNRI-85, model 94, which have been made by another producer, having as main material for the body of tamping tool and the active part (tine) of this, the alloy steel 42MoC11. The active part (tine) of a tamping tools, in areas which are the most stress at wear (abrasive wear s.a.), have been protected through welding with a hard material like EI 58 H electrode. The lot 2 (with 8 pieces) it have been identified with B21 ÷ B 28. The behavior of these tools, taking in account the weariness [mm] depending by [km] of tamping is present in Fig. 19. 5.3. Experimental researches in situ on the lot 3

of the tamping tools

The eight tamping tools type BNRI-85, model 94, which were presented above, after it work until to the admissible limits (see chapter 4), it has been reconditioning at the active part (tine) through welding, with two materials: 4 pieces with EI 58 H electrode, which have been identified with B21 (R1) ÷ B 24(R1) and 4 pieces with EI 16 Mn electrode, which have been identified with B25 (R1) ÷ B 28(R1). The behavior of these tools, taking in account the weariness [mm] depending by [km] of tamping is present in Fig. 19. CONCLUSIONS

- Designing a tamping tool and checking of this, to the different stress, with especially CAD soft, can offer many advantages, possibilities and reduce a lot of time and more accurate results.

- The new composite material with tungsten carbide, on which we have proposed, has a good potential and goods properties for wear, being chip and use the waste from different damage parts from tungsten carbide.

- In comparison, the average of weariness of tamping tools, after 9 km, with new composite material (with tungsten carbide) for the tine (lot 1: G4, G6, G8 (7)) is with 4,5 times smaller than the average of weariness of new tamping tools (lot 2: B21÷ B28) and with 6,5 times smaller than the average of weariness of reconditioning tamping tools (lot 3: B21 (R1) ÷B28 (R1)). In the end, the average of lastingness for lot 1 (G4, G6, G8 (7)) is with 2,8 times bigger than average of lastingness for lot 2 (B21÷ B28) and lot 3 ((B21 (R1) ÷B28 (R1)).


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This fact, make the possibility to reduce the cost of a tamping tool, a tamping operation and maintenance of railways.

Fig.19. The wear’ curves of the active part (tine) for

experimental tamping tools REFERENCES [1] I.C. Popescu, Introduction in computer aided analysis of the process

equipments, Printech Publisher, ISBN 973- 652- 951- 7, Bucharest, (2004)

[2] I.C. Popescu, T. Prisecaru, B. Finite elements Analysis of Pressure Equipment, Computer Aided Engineering Solutions for Design, Analysis and Innovation, (ANSYS & FLUENT User Group Meeting), 26-27 Aprilie 2007, Sinaia

[3] P. Georgeoni, N. Arnici, I.C. Popescu, and s.a., Using the isostatical pressing at the manufacturing of big machine parts by high performances from sintered metallic carbides, Metallurgical Researches, ICEM, Vol.26, page. 463 - 475, 1985, Bucharest.

[4]P. Georgeoni, I.C. Popescu, Considerations regarding to manufacturing of machine parts from metallic carbides type WC-Co with A.I.P. destination, Metallurgical Researches, ICEM, Vol.26, page. 477 - 483, 1985, Bucharest.

[5] V.V.Jinescu, I.C. Popescu, Reactors by very high pressure with the

elements manufactured from the tungsten carbides and cobalt, Chemistry Review, nr. 12, 1997, page. 981 - 991, ISSN 0034-7752, (ISI-MJL 7569);

[6] V.V.Jinescu, I.C. Popescu, Reactors by very high pressure with the elements manufactured from the tungsten carbides and cobalt, II, Chemistry Review, nr. 1, 1998, page. 56 - 63, ISSN 0034-7752, (ISI-MJL 7569);

[7] P. Georgeoni, I.C. Popescu, M. Istrătescu, L. Argeşanu, The behavior of different types hardness alloys from WC – Co system, used at manufacturing of dies for reactors by very high pressure, Mechanical Breakage, nr. 9, page. 8 - 14, 2000, ISSN 1453-8148;

[8] Cr. Besleaga, Contributions regarding to increase the lastingness of the tamping tools, Doctorate thesis, 625.144.5(043-2876) B-UP 1, Bucharest,(2006)

Ciocane BNRI - 85

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 [km]

[mm] G4

G6

G8(7)

B21

B22

B23

B24

B25

B26

B27

B28

B21(R1)

B22(R1)

B23(R1)

B24(R1)

B25(R1)

B26(R1)

B27(R1)

B28(R1)


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INTELLIGENT MECHATRONIC EQUIPMENT FOR VECTORIAL MASO - KINETOTHERAPY

T. S. Craciunoiu1, V. Avramescu2, I. Stoian3, C. Dumitru4, C. H. Orasanu5, R. Grejdanescu6, L. T. Paun7 , T. M. Muntenu8, O. Surdu9, V. Mihailescu10

1, 2, 3, 4, 5, 6, 7SC ICTCM - Mechanical Engineering and Research Institute SA, Bucharest, Romania

[email protected], [email protected], [email protected], [email protected] 8SC Mecanica Ceahlau Piatra Neamt, Piatra Neamţ, Romania, [email protected]

9Balnear Sanatorium and Recovery Techirghiol, Constanta, Romania, [email protected] 10Professor Constantin Popovici Foundation, Bucharest, Romania, [email protected]

REZUMAT Procesul de recuperare a persoanelor vârstnice sau cu dizabilităţi reprezintă o problemă majoră cu implicaţii în mediul social şi în mediul medical ca urmare a complexităţii tratamentului, a duratei acestuia, a standardelor aparaturii şi echipamentelor specializate capabile. Echipamentele mecatronice inteligente de monitorizare a bolnavilor, a persoanelor cu disabilităţi şi a vârstnicilor au devenit o necesitate imediată, piaţa mondială oferind o largă paletă de sisteme de acest gen, de la simple până la complexe. Fiecare persoană (mai mult sau mai puţin, mai devreme sau mai târziu) are nevoie de tratamente postoperatorii, recuperatorii sau de vitalizare, echipamentul mecatronic (pat reglabil asistat) propus a se realiza, prin multifuncţionalitatea sa, fiind necesar, în special, în Sanatorii de recuperare (indiferent de afecţiunile pacienţilor) dar şi în spitale pentru situaţii postoperatorii. Important de precizat este faptul ca aceste echipamente mecatronice cu aplicatii medicale au integrate sensori si sisteme speciale care le confera multifunctionalitate si inteligenta.

ABSTRACT The recovery proces of elderly or disabled person is a major problem with implications on the social environment and on the medical environment due to the complexity of treatment, its duration, standard equipment and specialized capable equipment. Intelligent mechatronic equipment for monitoring patients, persons with disabilities and the elderly have become an immediate necessity, the world providing a wide range of such systems, from simple to complex. Each person (more or less, sooner or later) needs to treat post recuperator, the mechatronics equipment (assisted adjustable bed) proposed to achieve through its multimunctionalit, is necessary, particularly in recovery sanatoriums (regardless of the conditions of patients) and in hospitals for postoperative situations. Important is that these mechatronic equipment with medical applications have integrated sensors and systems which gives them the special multifunctionalitaty and intelligence. CUVINTE CHEIE: echipamente mecatronice, echipamente inteligente, pat reglabil asistat, maso-kinetoterapie vectoriala KEYWORDS: mechatronic equipments, intelligent equipments, assisted adjustable bed, vectorial maso kinetotherapy

1. INTRODUCTION The recovery process of the old person or with disabilities is a big problem for social environment due the integration in time and with good results of the person with disabilities, but also for medical environment due the treatment complexity and its duration, directly minded by the specialized apparatus and devices able to assure the new types of treatment.

The intelligent mechatronic equipment achievements for monitoring patients, persons with disabilities and the elderly has become an immediate necessity, the world providing a wide range of such systems, from simple to complex, only the most complex are multifunctional. Because almost everyone (more or less, sooner or later) needs to treat postoperator, recovery or vitality, the mechatronic equipment (assisted adjustable bed) proposed to achieve, by its multifunctionality,it is very necessary


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especially in health recovery (regardless of patients' conditions) even in the hospital for postoperator situations. 2. OPPORTUNITIES - Equipping recovery sanatoriums, regional and local

centers, hospitals for postoperator situations, university clinics and other health network, for specific affections;

- The priority range is for recovery and social reinstatement of the person with sever affections, but also for the postoperator situations;

- The product is an adjustable bed, multifunctional, and assisted which covered the entire spectrum of recovery and postoperator processes, able to be equipped with accessories;

- The equipments which will come within the adjustable bed may be developed as separate products, with high performance.

3. ARGUMENTS - The need to equip the recovery sanatoriums, regional and local centers for recovery, hospital units for portoperator situations, medical practices, university medical centers, field units (mobile) etc.; - The large number of potential users around the world and especially in our country for such complex devices / systems could be both an extremely valuable, even critical, to increase the life quality; - The social impact will be big enough, by increasing the medical comfort, especially that at present at the medical treatment and recovery beds are sometimes only a maximum of three functions; worldwide are adjustable beds with up to six functions; - In Romania, at the moment, is not any type of adjustable or assisted bed with minimum function corresponding of recovery; - The scientific and technical fields remarkable in electronics, informatics and robotics (especially about the last two decades), are also possible and increasingly necessary, the execution of some assisted adjustable beds/devices, highly complex, performance and miniaturized; - Reducing the high social costs (and proceeding increase), related to the accidents during current processes by the recovery process and the reduction of the medical staff efforts (surgeon, nurses, etc..) before, during and after completion of medical process; - Solving the urgencies, complex cases, thus avoiding the seriated interventions, with the loss of important time in terms of urgency and avoiding the potential aggression during the medical process for recovery / postoperator; - Facilitating the medical process (recovery, postoperator etc.) in multidisciplinary teams; - Increased the operator comfort, through the possibility of patient positioning and devices as needed, but also for the patient by bed characteristics, made from a material with low hardness, which follow physiological curvature, with cushion of air / liquid,

with variable pressure and bearers of soft materials, with a high degree of movement, allowing position adjustment according to the individual look and avoids the appearance of decubit lesions during prolonged recovery treatments. 4. REQUIRMENTS The assisted adjustable bed, for recovery, must to perform the following conditions: • To be safe, performance and reliable with a large

range of accesories; • To allow the patient an optimal position for

achieving some medical processes specific to recovery and postoperator treatments;

• To ensure a proper positioning of the patient and to the expert team for achieving the different medical technique;

• Provide an additional access to the used supplementary equipment;

• Have in its support for X-ray cassette; • To be radiotransparence in order to allow the

passage of X rays; • Provide the access to the X-ray on the full length bed,

necessary for carrying out different explorations; • To allow the longitudinal arrangement of the

upper part of the bed up to 25 cm, for the optimal use of X-ray amplifier;

• To allow for any type of medical process; • To have the opportunity to annex additional

devices (supports for instruments with fixed position, additional light sources, devices for members or spine elongation);

• Be made by a material with low hardness, which follow physiological curvature;

• To contain the cushion of air or liquid with variable pressure in order to avoid the appearance of decubit lesions during prolonged medical processes for recovery / postoperator;

• To allow a high degree of freedom of movement; • The cushions should be removable, waterproof

and antistatic; • The bed area should be fine, smooth in order to

optimize the cleaning and disinfection; • The support for head should be detachable to have

servo attended dual regulation and compensation for integrated weight (optional);

• The support for shoulders and back should be servo attended adjustable and to allow the balancing and wheelwright (optional);

• The middle portion of the bed must contain elevators for optimal positioning of the patient;

• To include support for decubit lateral position (right/left); • To have detachable support for pelvicpodal legs,

with servo attended adjustable, allowing balance and turning for the thighs for patient positioning in gynecology position (optional);


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• The supports should be made of a solid material, but soft in order to avoid the decubit injury during prolonged recovery processes;

• The supports must have a high degree of freedom to be adapted according to individual physical particulars of the patients;

• To include a silicon metal frame that can be positioned the upper members;

• To contain seats that allow the attachment of various devices and accessories;

• To have three elastic belts for fixing the patient by bed, with mobile position (chest, abdominal and pelvic), required for recovery processes which required extreme positions;

• Have a good maneuverability in order to allow an easy movement of the bed and the patient in the treatment / postoperator room or beyond;

• To have 4- mobile double wheel, antistatic, with caps against liquids;

• To have an auxiliary wheel for precise movements; • Wheels must be able to lock; • To have a pedal with three positions for ahead

straight, free rotation motions and central brake; • To include detachable components (bed board)

that can allow the carriage of the patient for suplimentary investigation without the risk of intempestive handle in maximum conditions of security.

5. GENERAL DESCRIPTION The proposed multifunctional, assisted and adjustable bed falls into the category of multifunctional medical mechatronic equipments; being composed of multiple adjustable platforms folding independently operated and controlled by servomotors, can perform a wide range of movements. It is intelligent mechatronics equipment for monitoring patients, the disabled and the elderly person, consisting of multiple platforms operated independently by folding servomotors (actuators) ordered on the basis of a specialized software or from the console controller. Platforms will be covered with pneumatic mattresses with the possibility of individual change of pressure. The actuating and adjustment of the bed as medical required or patient request shall be made relatively easily and gradually through remote operation or by using an attached software. The bed is multifunctional due its multiple degrees of freedom and its possibilities to extend them. The degree of maintenance is increased due the function of the command and dialogue. The multifunctional assisted adjustable bed (experimental model), designed modular, can be easily adapted to various functions required by the methodology of treatment, or postoperative recovery, can

develop a family of beds from simple functions to multipurpose; also the bed can be equipped with various smart devices and accessories, strictly functional. Also, the bed is equipped with special control systems, including monitoring of the medical process. 6. EXPERIMENTAL MODEL Technological characteristics:

- - Overall size: 2150 x 970 mm - - Size mattress : 1950 x 850 mm - - Platform height (without mattress): 550 – 950 mm - - Maximum useful load: 300 kg

Functional characteristic: - - sectors numbers of the mattress support: 5 - - angle of inclination head support: ±150 - - angle of inclination back support: 0 – 700 - - angle of inclination upper leg support: 0 – 400 - - angle of inclination inferior leg support: 0 – 200 - - maximum angle for lifting on z: 15-200

- angle of inclination of the platform on x: ±200

Figure 1. Experimental model

CONCLUSIONS The project areas are important to ensure maximum health of the population, so through the act of medical intervention, including surgery and through the recovery process, the market for such equipment are constantly increasing due to the permanent need to facility in accordance with scientific research, new medical techniques and technological developments. REFERENCES [1] Project “MASOVECH”–Contract 208/2008 within National

Program INOVARE; [2] Dubey G.K., Doradla S.R., Joshi A., Sinha R.M.K.,

”Thyristorised Power Controllers”, Willey Eastern, 1986; [3] Dubey G.K., ”Power Semiconductor Controlled Drives”,

Prentice-Hall, Inc., 1989; [4] Fransua Al., Măgureanu R. ”Electrical actuation and

machines”,. Tehnical Editure, 1986.


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Quick Info Fast, quantitative diagnostic reader offers potential for thousands of medical tests This medical reader can perform diagnostic tests on any bodily fluid that attenuates light, such as blood, urine, sputum, or other fluid. Thousands of potential tests are possible, including immunoassay, colorimetric/chromogenic tests, HbA1c, cholesterol, HCG, osteoporosis calcium levels, and many more. While most physicians have easy access to lab tests, those tests can be slow and expensive. Consumer versions of tests are inaccurate and have limited scope, and often involve sending a sample to a lab. Physicians, PAs, Emergency Rooms, EMTs, patients, visiting nurses, and caregivers may all need access to quick, accurate tests without waiting for results and making callbacks. Some chronic tests (such as HbA1c for diabetics) require the mixing of reagents, and so are difficult to do athome. This all-in-one diagnostic reader can handle such tests and report results in as few as ten minutes. The prototype performs three identical tests on a single whole-blood sample for accuracy; but a greater number of simultaneous tests could be performed, or a battery of tests could be performed on the same sample.Programming and circuit board design determines the tests that an individual unit performs. All sample handling takes place inside the device. Prototypes indicate that the device will be inexpensive to build.A unique lancet draws blood for the prototype system. It slices the skin and creates a pressure differential to avoid injuring the red blood cells by “milking” (typical of finger sticks). In the prototype, one-button activation isolates a specific region of the Pre-Analytic System, transfers the plasma sample to the main test strip, applies diluents to it, and activates the electronic test protocol. Different activities could be designed into the unit for different tests. Lab-scale production of fully functional injection-molded devices has been undertaken for proof-of-concept, but Kimberly-Clark does not envision that the current apparatus is the final product. Benefits Summary - Low-cost to manufacture; low-cost per test. - Performs any test or assay on any bodily fluid that attenuates light. Thousands of different assays could be

designed into the system. - No sample preparation required. Test strips are consumables. - All-in-one unit. The system obtains the sample (prototype uses a special lancet to draw blood), meters out the

necessary sample volume, transfers that volume to the sample area, and quantifies up to three different tests.Kimberly-Clark believes that this system is the lowest cost approach to performing all these tasks in a singleunit.

- Intended for use with an OLED (organic LED) display. OLEDs are bright. The display requires no additionalback-lighting. It offers the opportunity for scrolling, text, graphics, and full color -- more variety and more information than the fixed-position text and images on an LCD display.

- A special lancet was developed for the device that does not damage red cells to be used in testing. Analytesother than blood may require a different sample acquisition system.

Development Summary Lab scale, injection-molded apparatuses can be made available to interested parties. Kimberly-Clark does not envision the current apparatus to be the final product; however, it is fully functional. Technical reports have beencompleted, along with market data. Some physician studies have been completed. IP Summary This technology is supported by 20 US patents. The most recent year of issue is 2008.

(source: [email protected] / http://www.yet2.com/app/list/techpak?id=54472&sid=90&abc=0 )


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MULTIFUNCTIONAL SURGICAL TABLE

T. S. Crăciunoiu1, V. Avramescu2, A. V. Ciurea3, C.M. Birtu4, A.M. Croitoru5, V.T. Grigorean6, I. Lung7, R.S. Crăciunoiu8, L.T. Păun9, R. Grejdănescu10

1, 2,4,5,8,9,10 SC ICTCM - Mechanical Engineering and Research Institute SA Bucharest, Romania

e-mail: [email protected], [email protected], [email protected]. [email protected], [email protected], [email protected]

3 Bagdasar-Arseni Clinic Emergency Hospital, Bucharest, Romania, [email protected] 7 The National Institute of R-D in Mechatronichs and Measurement Technique – INCDMTM, [email protected]

REZUMAT Cercetările efectuate în acest proiect au avut ca obiectiv principal dezvoltarea conceptuala a unor modele integrate, complexe, performante de echipamente complexe care sa raspunda necesitatilor persoanelor cu grad sever de dizabilitate in scopul reducerii impactului psihologic al acestora si integrării lor socio-economice, in general prin asigurarea unui transport independent si realizarea de modele experimentale ale unor scaune rulante, manuale sau actionate electric, cu structuri modulare, flexibile, cu grad mare de adaptabilitate. Pe baza modelelor conceptuale se poate dezvolta in viitor o gama diversificata de astfel de echipamente, cu functiuni simple sau complexe, manuale sau actionate, fixe, pliabile, cu accesorii speciale, cu posibilitati de adaptare a lor functie de gradul de dizabilitate, in scopul asigurarii deplasarii sigure a persoanelor cu deficiente neuro-locomotoare.

ABSTRACT One of the surgical system priorities is the need to ensure the patient safety and creating the optimal conditions of the operator, for example: the need to adopt some various positions of the patient or the need to change the intraoperator position of the patient. There are better surgical tables, made by several segments that can be operated independently. Also is developing a wide range of intelligent devices and accessories to allow expansion of the medical act, ensuring precision, maneuverability, accuracy, patient safety, patient and operator comfort. A particular case is the development of mechatronic equipment in medical applications, such as mechatronic systems for vectorial maso- kinetotherapy recovery treatments. The importance of this is that these mechatronic devices with medical applications have integrated sensors and special systems which gives them the multifunctionality and intelligence.

CUVINTE CHEIE: dizabilitati neuro-locomotorii / cardio-respiratorii, scaun cu rotile, echipamente pentru transportul independent al persoanelor cu grad sever de disabilitate KEY WORDS: surgical devices and accessories, multifunctional intelligent surgical devices, surgical tables, stand-up wheelchair, stand-up power wheelchair, surgical intervention, robotized interfaces.

1. INTRODUCTION Currently, the world market for operating tables offers a wide range of systems, from the simplest with fixed support and only three sections, to the most complex, with mobile and 8-9 sections electrically or hydraulically actuated through panels with direct commands or by remote control (usually with RI). These surgical tables are generally targeted at a specific pathology (traumatology, gynecology, orthopedics etc.), only the most complex is truly versatile.

On the international level, the surgical devices and accessories assure all the requirements of the medical and allow achievement of peak performance for the human operator. There is a concern for resolving the technical and surgical interventions and are ongoing efforts to rethink the technical solutions, to monitor the medical act and the patient, to allow the active control by the operator for the neded devices and accessories. They are equipped with multiple sensors and is monitored by means of computer and some software as appropriate, including interfacing with specialized robots.


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Making such devices and accessories performing surgery would allow the operator to be more secure and to avoid the appearance of numerous and postoperative intraoperator complications, with direct implications on the growth of the medical quality and improve health of the population. 2. OPPORTUNITIES a. Equipping hospitals, university clinics and

other health network, including the recovery; b. The priority is the surgical area, specific to the

surgery rooms in hospitals or specialized clinics;

c. The product is a multifunctional surgical table covered entire spectrum of surgery, the table can be equipped with accessories necessary for each type of intervention;

d. Equipment which will come within the surgical devices may be developed as separate products, with high performance.

3. ARGUMENTS The need to equip hospital units, medical

practices, university medical centers, field units (mobile) etc.;

The large number of potential users around the world and especially in our country for such devices / systems could be both an extremely valuable, even critical, to increase the life quality;

In Romania, at the moment, is not any type of surgical table with minimum function corresponding of surgery;

The scientific and technical fields remarkable in electronics, informatics and robotics (especially about the last two decades), are also possible and increasingly necessary, the execution of some devices / surgical systems, highly complex, performance and miniaturized;

Reducing the high social costs (and increasing in civilized countries), related to the accidents during surgical processes and the reduction of the medical staff efforts (surgeon, nurses etc.) before, during and after completion of surgery;

Solving the urgencies, complex cases, thus avoiding the seriated interventions, with the loss of important time in terms of urgency and avoiding the multiple anesthetic - surgery aggression;

Facilitating the surgery interventions in multidisciplinary teams;

Increased the operator comfort, through the possibility of patient positioning and devices as needed, but also for the patient by characteristics table, made from a material with low hardness, which follow physiological curvature, with cushion of air / liquid, with

variable pressure and bearers of soft materials, with a high degree of movement, allowing position adjustment according to the individual look and avoids the appearance of decubit lesions during prolonged surgery intervention.

4. REQUIRMENTS The multifunctional surgical table must to perform the following conditions: • To be safe, performance and reliable; • To include a wide range of accessories; • To include a number of detachable

components, that can allow the positioning of the patient in the optimal position to achieve surgical complex or multidisciplinary teams;

• To ensure a proper positioning of the patient and to the operators team for achieving the different surgical techniques;

• Provide an additional access to the used equipment during surgery;

• Provide the access to the X-ray on the full length table, necessary for carrying out different intraoperator explorations;

• Have in its support for X-ray cassette; • To be radiotransparence in order to allow the

passage of X rays; • To allow the longitudinal arrangement of the

upper part of the table up to 25 cm for the optimal use of X-ray amplifier;

• To allow for any type of surgery; • To have the opportunity to annex additional

devices (supports for instruments with fixed position, additional light sources, devices for members or spine elongation); for this purpose should be provided with special seats for fixing these devices, located on its sides;

• Be made by a material with low hardness, which follow physiological curvature;

• To contain the cushion of air or liquid with variable pressure in order to avoid the appearance of decubit lesions during prolonged surgical interventions;

• To allow a high degree of freedom of movement;

• The cushions should be removable, waterproof and antistatic;

• The area and profiles of the surgical table should be fine, smooth in order to optimize the cleaning and disinfection of the entire operation table;

• The support for head should be detachable to have servo attended dual regulation and compensation for integrated weight;

• The support for shoulders and back should be servo attended adjustable and to allow the balancing and wheelwright;


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• The middle portion of the table must contain elevators for optimal positioning of the patient;

• To include support for decubit lateral position (right/left);

• To have detachable support for pelvicpodal legs, with servo attended adjustable, allowing balance and turning for the thighs for patient positioning in gynecology position;

• The supports should be made of a solid material, but soft in order to avoid the decubit injury during prolonged surgical interventions;

• The supports must have a high degree of freedom to be adapted according to individual physical particulars of the patients;

• To include a silicon metal frame that can be positioned the upper members;

• To contain seats that allow the attachment of various devices for surgical interventions (for example the Mayfield cradle, the sterol station cradle etc..) in the previous table;

• To have three elastic belts for fixing the patient by table, with mobile position (chest, abdominal and pelvic), required for surgery interventions which required extreme positions;

• To include a hydraulic pump for positions up, down and sideways, which can be handled by the foot of the surgeon as needed (optional);

• Have a pre-selection for positions up, down and sideways (optional);

• To have a remote control with batteries for electro-hydraulic adjustment the movements in combination with the preselector;

• Have a good maneuverability in order to allow an easy movement of the table and the patient in the operating room or beyond;

• To have 4- mobile double wheel, antistatic, with caps against liquids (optional);

• To have an auxiliary wheel for precise movements (optional);

• Wheels must be able to lock; • To have a pedal with three positions for ahead

straight, free rotation motions and central brake;

5. GENERAL DESCRIPTION The main objective of the research project was developing an integrated concept of surgical devices and multifunctional accesories, and a surgical table, to ensure the comfort and performance in terms of safety for the patient, and to ensure also the comfort of the operator. This device will find application in all branches of surgery, but more in neurochirurgical for two reasons: 1. Neurosurgical interventions have a long

development (up to 8-10 hours), while the

patient is kept in the same position. It must be a comfortable surgery table, to assure an uniform distribution of the mechanic pressure exerted on the tegument, an electronic monitoring and continuous recording of vital parameters and storing them for further interpretation; in this way it may prevent such injuries that can occur (peripheral paresis, ischemia of the limbs, etc.).

2. The need to change the position of various segments of the table or in whole, in order to better view the lesion intraoperator microscope. This involves the achievement of an automatized surgical table, with more degrees of freedom and with the possibility of manipulation by verbal command performed by the surgeon during surgery. Specific to the neurosurgical interventions, the surgical table should have a special retainer for a proper positioning of the head and set to cephalic extremity during surgery. Also should have, in addition, the possibility of rotation of the head to the verbal command of the operator, which would facility the surgery intervention with a better view of lesion in the operator field.

The resulted surgical table as experimental model and proposed to be in manufacturing it falls into the category of multifunctional tables, being composed of 8 sections which are electro mechanic and manually actuated and could perform a wide range of movements. The column of supporting the surgical table is actuated by a microprocessor and is mounted on a metal base with calculated dimensions and mass so as to ensure the optimal system stability. Both the central column and the support base are made of stainless steel. The central column contains inside all the functional elements needed to positioning the surgery table (mechanical and electronic circuits, batteries, transformer, rectifier, etc.). All the movements of the table leg are coordinated by a microprocessor and are assured of electromotive protected against the production of sparks because of the working environment rich in gas and volatile liquids substances. The foot of the surgery table is protected from infiltrations of liquids, primarily due to its need for daily disinfection solutions in terms of active biologically. The table leg degrees of freedom in motion surgery include:

- horizontal lateral transfer; - horizontal rotation; - vertical extension.

The surgical table (experimental model), being designed modular, can be easily adapted to various surgical functions and / or appropriate treatment of specific health; it can develop a family of surgical tables from simple functions to multipurpose, while surgical table may be equipped with various devices and accessories, intelligent and strictly


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functional. It pursues to equip the surgical table with control systems, including voice command. He deserves to be submitted to resolve, through the concept developed, the following issues: - Preventing the intraoperator complications that

can occur as a consequence of particular neurosurgical interventions. One of the objectives is to monitor the mechanical pressure that occurs at the contact surface of body with surgical table;

- Equipping the surgery table with a recording system of different parameters of the patient to be stored and post operator analyzed;

- The need for movement in various plans of the table, during surgery, in order to obtain an adequate exposure of the interest area in operator microscopic field. The main operator, depending on the image of the operator microscopic, decides the time and the magnitude of the table movement. The development of a verbal command system would allow a greater operator comfort for surgeon;

- Establish a system of fixing the extremity cephalic, with the possibility of controlled movement to the head rotation is another goal; achieving this would allow the full access to the operator field, without needing the permanent movement of the microscop during neurosurgical intervention.

The surgical table, modular designed and adapted for various surgical accessories specific to the medical act, is equipped with the table itself equipped to assist the patient and table leg; both systems are operated independently, with possibilities of moving vertical and horizontal, and inclination of the various modules. 6. EXPERIMENTAL MODEL Technological characteristics: max. height / / min. height: 1060 / 670 mm; length x width: 1890 x 530 mm; maximum payload: 300 kg;

Functional characteristics: The degrees of freedom in moving the surgical table leg include: - back lifting /moving down (O3): +80º/ -45º, - (X) head lifting /moving down (O4): +90º/-90º, - legs lifting /moving down (O5): +15º/ -70º, - (X)legs farness (O6) 0º / +60º, - head lifting/moving, - down–additional (O7): +90º/ -90º.

Fig. 1. Experimental model

Fig. 2. Table horizontally positioned

Fig. 3. Table longitudinal inclined+350

Fig. 4. Inclined table for kidney intervention


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Fig. 5. Antitrendelenburg

(the organ tackle from supramezocolicstage

Fig. 6. Gynecology /urology

Fig. 7. Percutanat nefrolitopexie

Fig. 8. Shoulders supports adapted on the surgical

table (ex.: MAQUET Germany)

Fig. 9. Foot supports adapted on the surgical table

(ex.: MAQUET Germany)

Other general characteristics: Automated: the material which is formed must

provide the following qualities: slight, easy to clean (the edges rounded, component parts with simple design) & radiotransparence (carbon fiber)

Consists of segments, modular. Extensible. Allowes the exertion of an uniform pressure -

Pillows (foam): radiotransparences, with absorbition resistance, thermal insulation,


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electrical insulators, sterilized, disinfected, with uniform pressure

Allowes the sliding the mobile apparatus X-ray „C-arm” type: (except in the place to be fixed the column support) with maximum areas of interest: Center yead, Cervical, Chest column & Lumbar column

Allowes the insertion and fixation of X-ray cassettes

Thermic isolated (allowes electric recording and stimulations)

Verbal command Flexibility (degrees of freedom).

7. AREAS OF USE A representative field of use is neurosurgery which is interested to develop some devices for increasingly more complex for fixing the head in various positions required by the different types of operators. These are just a few examples, taken from neurosurgery, but the applications of these multifunctional intelligent devices and accessories could satisfy requirements more comprehensive given by directions specific to the medical surgery. Other areas of use: general surgery, gynecology-urology, orthopedics, traumatology, cardiology, dentistry, etc., with patient positioning. 8. DEVICES AND ACCESORIES OF THE SURGICAL TABLES The multifunctional intelligent devices and accessories are to solve some of the additional requirements of the medical process and patient and operator comfort, representing an adaptation of medical equipment and an extension of its functions. Equipped with sensors and operated in order (part one) they ensure a high quality of the medical process and confers its accuracy, precision, safety, security etc. Are multifunctional and intelligent, answering directly to the operator desire and providing the field and the necessary conditions for the development of the medical process. In some cases, the intelligence are dominate and the functions area are strictly delimiting them being specialized. Collect information from the intervention and, depending on the results of analysis, may be redesigned or adapted accordingly.

9. CONCLUSIONS The project area is the surgical activities specific to the surgery rooms in hospitals or specialized clinics. The product is a multifunctional surgical table that covers the entire spectrum of surgery, can be equipped with accessories necessary for each type of intervention. A series of equipment that will come within the surgical devices may be developed as separate products, with high performance. 10. BIBLIOGRAPHY: [1] Project “CHINTEH” – Contract 191/2006 – developed between 2006-2008 within CEEX National Program – Viasan. For more information, please see – http://www.ictcm.ro/Ceex2006/CHINTEH/index.html [2] Dubey G.K., Doradla S.R., Joshi A., Sinha R.M.K., ”Thyristorised Power Controllers”, Willey Eastern, 1986; [3] Dubey G.K., ”Power Semiconductor Controlled Drives”, Prentice-Hall, Inc., 1989; [4] Fransua Al., Măgureanu R. ”Electrical actuation and machines”,. Tehnical Editure, 1986.


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SYSTEM FOR DATA AQUISITION AND ANALYSIS OF THE KINEMATICS OF THE GAIT

FOR THE COMAND OF A ROBOTIZED ORTHOTIC SUIT

F. Alexiuc1, V. Avramescu2, G. Onose3, L.T. Paun4, R. M. Nita5, C.H. Orasanu6, R. Grejdanescu7, C. N. Nicolau8, A. M. Croitoru9, R. S. Craciunoiu10

1, 2, 4, 5, 6, 7, 8, 9, 10 SC ICTCM - Mechanical Engineering And Research Institute SA, Bucharest, Romania [email protected], [email protected], [email protected], [email protected], [email protected],

[email protected], [email protected], [email protected], [email protected] 3 Bagdasar-Arseni Clinic Emergency Hospital, Bucharest, Romania, [email protected]

REZUMAT Cercetările efectuate în cadrul proiectului „Sistem informatic bazat pe achizitie date si metode avansate de decizie in timp real pentru comanda si controlul unui costum ortetic robotizat pentru asistarea persoanelor cu disabilitati ale aparatului locomotor” urmaresc realizarea unui software pentru achizitia datelor in timp real si luarea deciziilor pentru mentinerea ortostatismului si a echilibrului. Proiectul este realizat de un consortiu format din SC ICTCM SA, Spitalul Clinic de Urgenta Bagdasar-Arseni, UPB-CTANM, SC Neuron SRL si Tehnicom3D-ing SRL. In prima etapa a proiectului au fost achizitionate datele de miscare si anume: achizitia semnalelor analogice furnizate de potentiometrele amplasate in articulatiile costumului ortetic robotizat si achizitia semnalelor analogice furnizate de senzori de presiune amplasati pe talpa. Sistemul de achizitie date realizat poate fi utilizat in clinicile de kinetoterapie pentru evaluarea si recuperarea medicala a pacientilor. In cea de-a doua etapa se are in vedere simularea comportarii costumului ortetic robotizat in mediul virtual pentru a se studia comportarea costumului ortetic robotizat si a subiectului uman in vederea gasirea elementelor hardware si software care sa asigure desfasurarea in siguranta a miscarilor de ridicare-coborare, ortostatism, mers si echilibru, reactie la factori perturbatori etc.

ABSTRACT The researches which were made in the project “Informatics system based on data acquisition and advanced decision in real time methods for the command and control of an robotized orthotic suit in order to assist the persons with locomotors disabilities”, follow the achievement of a software for the data acquisition, in real time, and also the decisions making for keeping the orthostatism and the equilibrium. The project was developed by a consortium formed by SC ICTCM SA, Bagdasar-Arseni Clinic Emergency Hospital, UPB-CTANM, SC Neuron SRL and Tehnicom 3D-ING SRL. In the first stage of the project there were achieved the data related to motion: the acquisition of the analogical signals provided by the potentiometers displaced in the robotized orthotic suit’s joints and the acquisition of the signals provided by the pressure sensors displaced on the base of the foot. The data acquisition system can be used in the kinetotheraphy clinics in order to evaluate and medical recovery of the patients. In the second stage there is considered the simulation of the behaviour of the robotized orthotic suit in the virtual medium in order to study the behaviour of the orthotic suit and of the human subject in order to find the hardware and software elements which should assure the safety development of the ascension/descent movements, orthostatism, gait and equilibrium, reaction to the perturbing factors, etc. CUVINTE CHEIE: dizabilitati neuro-locomotorii / cardio-respiratorii, costum ortetic robotizat, orteze, kinetoterapie, ortostatism KEYWORDS: neuro-locomotors/cardio-respiratory disabilities, robotized orthotic suit, orthosis, kinetotheraphy, orthostatism


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1. INTRODUCTION

In the world there are several categories of persons with disabilities at locomotory level: paralyzed people at lower level, old persons with polidisabilities (neuro-myo-artro-kinetic, cardiovascular etc.).

These persons may not be prothesed (because they do not have my legs which were cut off), and to help them, there would be required orthosis (devices which "dress" the sick members) able to pick up sick people, to keep the orthostatism and to "walk" maintaining the equilibrium.

According to statistics of the National Agency of Persons with Disabilities, on 30 November 2005, compared to the total number of persons with disabilities, the number of people integrated in the socio-economic context is very small.

Therefore, we consider that the achievement of some assistive complex orthotic devices could be good from all points of view for many people with physical and somatic disabilities (in total over 125000 people), representing an extremely valuable, even crucial method, for increase the quality of life and at the same time, an important way of reducing the pressure of the high costs of medical and social care related to budgets on health. 2. TENDENTIES AT WORLD WIDE LEVEL

Remarkable scientific advances, especially in areas as: recovery / posturology / assistive an recovery medical technologies, robotics, cybernetics and multifunctional materials, have between the objectives and in the same time, the main appliance directions, the area to assist / recovery for people with severe disabilities at apparatus: neuro-myo-artro-kinetic, circulatory and / or respiratory.

This objective becomes possible by carrying and using of devices / systems, advanced and miniaturized and which can functionally replace the deficit of sensitivity and neuro-motor control, central and peripheral and / or the capacity of the circulatory and respiratory apparatus, to support bio logistic the somatic muscles during the current efforts of ortostatism and gait.

Although at worldwide level there are many researches to achieve this goal, biped robots with performing orthostatism, walking, active equilibrium and asset cvasi identical with the human ones or exoskeleton to amplify the forces of valid persons, until now there is not any functional robotic orthosis for the lower level.

In November 2008, after 9 years of research, in firm HONDA (Japan), was designed a robotic orthosis which seems to solve some of the problems.

The orthosis is 6.5 kg, it can be easily "shoed" and it is formed by a motor, computer, motion sensors and a Lithium Ion battery.

The achieved orthosis is not meant for people with severe disabilities of the locomotors system (such as paralyzed people), because it does not maintain the equilibrum, but only "help" the muscle, as was said at the HONDA "a walking assistant” which "make easily the gait stress”. 3. TENDENCIES IN ROMANIA

In Romania, the researchs in this area began in 2004 at SC ICTCM SA in collaboration with SC ICPE SA, UPB-Optimum, SC TEHNICOM SRL, The "C-tin Popovici” Foundation, SC INCDMF SA, SC CERTEX SA, Bagdasar -Arseni Emergency Clinic Hospital, in RELANSIN Program, for the achievements of components of a robotic orthotic suit.

In 2005 in the framework of CEEX there were made: modular structures of the mechatronic orthotic device, the equipment to compensate the weight and to recovery of energy, optimized solutions for action and power supply of the orthotic device’s modules, the textile structure for the interface with the contact skin areas of the assisted person, equipment to improve the circulation of lymphatic-venous return during walking.

In 2007 in the "Partnerships in Priority Areas" Program, it has been accepted to finance the project "Informatics system based on data acquisition and advanced decision in real time methods for the command and control of an robotized orthotic suit in order to assist the persons with locomotors disabilities” in order to achieve a software for data acquisition in real time and for making the decisions for maintaining the orthostatism and equilibrium during movement as: ascending/descending and walking.

The project was developed by a consortium composed of SC ICTCM SA, UPB-CTANM, SC NEURON SRL, TEHNICOM3D-ing SRL, Bagdasar-Arseni Emergency Clinic Hospital. 4. DATA AQUISITION SYSTEM AND ANALYSIS OF THE KINEMATICS OF THE GAIT IN OREDER TO COMAND A ROBOTIZED ORTHOTIC SUIT

In large lines, the algorithm which must be the base for the “learning” process of the gait, there is presented in the fig. 1.

The first stage of the process of learning is the acquisition of movement: the acquisition of analogue signals provided by the potentiometers located in robotized orthotic suit’s joints (designed by system ICTCM) (fig.2) and the acquisition of analogue


23

signals provided by pressure sensors placed on the base of foot (system achieved by SC NEURON SRL).

Through data acquisition system (sensors, data acquisition board NI USB-6225, LabVIEW) and the program "Write Data in file.vi, data are stored in data files.

For data analysis and processing, there was done the program "Read data.vi" (fig.3). The program shows both a global image of the signals provided by the potentiometers which are located in the robotized orthotic suit’s joints and the possibility of viewing each joint separately.

Developed data acquisition system can be used in clinics of kinetotherapy for medical assessment and recovery of patients.

To have a qualitative picture of movement and in order to analyze and simulate the pattern of movement which will be transmitted in the final to the drive motors of the orthotic suit’s segments, it was made the program “2D viewing of legs’ moving” (Fig.4).

With this program the acquired data are viewed on a "virtual patient". The two articulated structures, representing the legs, can be scaled to the anatomical dimensions of the subject with the cursors: femur length, tibia length, maleola length. The 2 structures may be delayed or superimposed to analyze the movement. They can be delayed the movements to follow the angles or to observe the moments when the patient's movement is different than normal. 5. RESULTS. IMEDIATE RESULTS

As shown in fig.1, the next stage of data acquisition and data analysis is to simulate the behaviour of the robotized orthotic suit achieved in a virtual environment.

Previously processed motion data are transmitted to a 3D model to study in virtual the behaviour of the robotized orthotic suit and of the human subject in order to find the hardware and software elements which have to assure the safe development of the movements: ascending/ descending, orthostatism, walking and equilibrium, reaction at perturbing factors.

Figure 1. The algorithm of the “gait learning” process

In this phase, the data acquired on the human subject will be refined so that the movements are smooth and uniform. Follow the isolation of a motion sequences that by rehearsal reproduces the continue movement and the conversion of data in the comand program of the motors that actuate the orthosis.

In the next phases of the project, the simulations, from kinematics point of view, will be filled with dynamic simulations to achieve the maintenance of orthostatism, of equilibrium during walking and recovery in case of imbalance.

With the ADAMS and LifeMOD software there will be made dynamic simulations of all human-robotized orthotic suit assembly for determining the forces and torques necessary to achieve, in terms of safety, the walking and equilibrium.

Also, in collaboration with the Bagdasar-Arseni Emergency Hospital, the researches in the field of data acquisition will be supplemented by systems for non invasive capture of the signals sent by the brain, by their filtering and their usage for the command of a robotized orthotic suit.

Figure 2. Data acquisition system for robotized orthotic suit

CONCLUSIONS

The project developed at ICTCM in collaboration with SCUBA and other partners, is intended to improve quality of life of persons with disabilities at the locomotors apparatus.

The ultimate aim of the project, which contains the presented system of data acquisition, is to achieve an autonomous system for command and control a robotized orthotic suit to assist/recovery the orthostatism and walking at people with neurological disabilities of the locomotive.


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The development and the application in the future of the results of this project will be for the approximately 40,000 patients with severe paralysis from our country - as well as for several million such patients in the world - a decisive factor for the huge increase of their quality of life and also for beneficial scientific collaboration in specific international programs.

Due to the particularities of the project, the research results that will be developed are mainly of social nature (in the sense that they will recover, in the future, for society, a large number of people considered "low") and economic (for the retarded person who became from "maintained by the budget" a person who can work according to his own possibilities and preparation). The solving of the problems related to gait will bring a rich experience for the participants in the project, including for young engineers and research teams of partners in the project, this experience can be used for solving other problems of disability, also opening the possibility of international cooperation. REFERENCES [1] Onose G., Cardei V., Avramescu V., Craciunoiu S.T.,

Dogariu C., Consideratii privind realizarea unui system ortetic robotizat pentru asistarea persoanelor cu disabilitati neuro-locomotorii./Considertations regarding the achievement of a robotized orthotic suit in order to assist the persons with neuro-locomotory disabilities, Ecologie Industriala/Industrial Ecology, No. 3-4 / 2004;

[2] Project SICCCOR, contract 11-075/2007, 2007-2011, opened. Quick Info 3M™ Ultra Hard Metric (UHM) Products 3M now offers a fully shielded socket connector in the Ultra Hard Metric (UHM) series that conforms to the shielded J2 connector requirements specified in the new draft CompactPCI(r) standard PICMG 2.30. This connector is fully matable to 2mm HM IEC 61076-4-101 headers. - Ultra Hard Metric (UHM) Connector - Ultra Hard Metric (UHM) Backplane Socket

Connector - Other High Speed Products

3M™ Ultra Hard Metric (UHM) Connector for Compact PCI PICMG 2.30 Applications

3M now offers a new fully shielded socket connector in the Ultra Hard Metric (UHM) series that is anticipated to conform to the shielded J2 connector requirements specified in a new CompactPCI® standard specified in PICMG 2.30. The 3M UHM connector that conforms to the PICMG 2.30 draft standard is:

Part Description Part Number Tech Sheet

Fully Shielded 2 mm Hard Metric B style Right Angle

Socket

UHM-S110B3-

5AP1-TG30

TS-2284

The UHM-S110B3-5AP1-TG30 connector is intended to be specifically designed for PICMG 2.30 applications.

The PICMG 2.30 CompactPCI draft standard is a next generation standard intended to seamlessly provide support for high speed serial IO such as PCI Express, SAS/SATA, Gigabit Ethernet, USB while leveraging end users’ existing investment in 3U and 6U CompactPCI computing platforms defined under an earlier standard defined under PICMG 2.16 Market Segments/Customer Applications.

Market Segments/Customer Applications - Embedded Computing - Industrial Control & Factory Automation - Medical - Communications - Military Computing

Summary of Key Features and Benefits - Expected to conform to PICMG 2.30 shielded J2

connector requirements; - High-speed socket connector – more than 7 Gbps

performance even when used with standard unshielded Hard Metric (HM) headers (from 3M or competition);

- Full shielding of signals or signal pairs minimizes crosstalk;

- 2 mm pitch offers intermateability and PCB footprint compatibility with standard HM designs leverages existing investment;

- High signal density – 63 signals per linear inch for the 5-row - optimizes PCB space;

- Unique dual beam contact design for high reliability.

RoHS* compliant with press-fit exemption The 3M UHM-S110B3-5AP1-TG30 connector is expected to conform to the shielded J2 connector defined for the System Slot in Compact PCI embedded computing systems defined under the PICMG 2.30 draft standard.

(source: http://dkc1.digikey.com/us/en/ph/mkt/uhm.html)


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INTEGRATED CONCEPTUAL MODEL OF A WHEELCHAIR, MADE BY THE DEVELOPMENT OF SOME COMPONENTS

THAT ARE PART OF ITS STRUCTURE

Grigore Stanca1, C.Dumitru2, C.H. Orasanu3, V. Avramescu4, G. Onose5 , L. Paun6 , R. Grejdanescu7 , R.M. Nita8 , R.S. Craciunoiu9 , I. Dimache10

1,2,3,4,6,7,8,9,10SC ICTCM - Mechanical Engineering and Research Institute SA,Bucharest, Romania

[email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]

5 Bagdasar-Arseni Clinic Emergency Hospital, Bucharest, Romania, [email protected]

REZUMAT Cercetările efectuate în acest proiect au avut ca obiectiv principal dezvoltarea conceptuala a unor modele integrate, complexe, performante de echipamente complexe care sa raspunda necesitatilor persoanelor cu grad sever de dizabilitate in scopul reducerii impactului psihologic al acestora si integrării lor socio-economice, in general prin asigurarea unui transport independent si realizarea de modele experimentale ale unor scaune rulante, manuale sau actionate electric, cu structuri modulare, flexibile, cu grad mare de adaptabilitate. Pe baza modelelor conceptuale se poate dezvolta in viitor o gama diversificata de astfel de echipamente, cu functiuni simple sau complexe, manuale sau actionate, fixe, pliabile, cu accesorii speciale, cu posibilitati de adaptare a lor functie de gradul de dizabilitate, in scopul asigurarii deplasarii sigure a persoanelor cu deficiente neuro-locomotoare. ABSTRACT The researches made in this project had as main objective the conceptual development of some integrated, complex, competitive models of complex equipments which to carry out the problems of the persons with a high degree of disabilitation for reducing their psychological impact and for their socio-economic integration, in general by offering them a means of independent transportation and the realization of the experimental models of some wheel chairs, that are hand power or electric power, with modular and flexible structures, with a high degree of flexibility. Based on the conceptual models can be developed in the future a wide range of similar equipments, with simple or complex functions, hand power or driven by other means, fix, foldable, with special accessories, with flexibility possibilities according to the disabilitation degree, for offering safety to the persons with neuro-kinetic deficiencies. Cuvinte cheie: dizabilitati neuro-locomotorii / cardio-respiratorii, scaun cu rotile, stand-up wheelchair, stand-up power wheelchair, echipamente pentru transportul independent al persoanelor cu grad sever de disabilitate Key words: disabilites neuro-locomotor / cardio-breathing, wheelchair, stand-up wheelchair stand-up power wheelchair, equipment for independent transportation of persons with a high degree of disabilitation

1. INTRODUCTION Elders’ share(over 60-65 years) from the entire population is closing today to a fifth, in many countries, including Romania, and an world scale foreseeing estimates that elders will „grow” to 25 %

in next 20 years, especially in highly-developed contries – which are most „demographic grown old”. First consequence of these demographic phenomena is the full growth – in number as in weight – of „great elders” group, in many cases over 80 y.o.; this demographic category due to its ample polipathology and high level of polidisabilities (neuro-mio-artro-kinetic, cardiovascular, respiratory, sensorial) has maximum potential of benefitiating from those


26

complex equipments which maintain functional authonomy, implicit life quality, no less than diminishing the costs assembly due to medical and social elder assistance, costs which should consume an oversized share of their resources. Other locomotory deficiencies category is the paralysis-generated one, meaning temporarily or permanently neurological control abolition over somatic and / or vegetative organism territory. Medium age for this kind of traumatisms is 33,4 years, medium value is 26, and so the overwhelming majority of para- and tetraplegic patients is constituted from(very) young people, situated at the very start of their professional and social productive life, this fact having a devastating psychological, family, professional and socio-economical impact. Taking in consideration these issues, the conceptual models developed had in view new conceptual solutions and specific modification of some classic components that are part of the wheel chair so as to create mobility, safety, accessibility and comfort taking in consideration that the patient need this mean of transportation, to increase his level of personal independence. 2. OPPORTUNITIES a. The group of „great elders” group, in many

cases over 80 y.o.; this demographic category due to its ample polipathology and high level of polidisabilities (neuro-mio-artro-kinetic, cardiovascular, respiratory, sensorial) has maximum potential of benefitiating from those complex equipments which maintain functional authonomy, implicit life quality, no less than diminishing the costs assembly due to medical and social elder assistance, costs which should consume an oversized share of their resources;

b. The group of paralysis-generated one, meaning temporarily or permanently neurological control abolition over somatic and / or vegetative organism territory, constituted from(very) young people, situated at the very start of their professional and social productive life, this fact having a devastating psichological, family, professional and socio-economical impact.

c. The increasing of the life quality respectively for 40.000 para- and tetraplegic plus hemiplegic Romanian patients;

d. Part equipments that can be developed also like independent parts, with high performances.

3. ARGUMENTS The necessity of assistance and / or recovery

orthostatic and walking for severely disabilitated elders and cardio – respiratory

insuficiency and / or neuro-kinetic hard deficiencies patients, which still keep total or partial nervous control on lower limbs; in these cases the equipment’s main goal is to compensate orthostatic selfmaintaining and walking capability,

The necessity of assistance and / or recovery orthostatic and walking for people having locomotory apparatus paralysis, no longer maintaining nervous control on voluntary movement of its various parts; different equipment’s modules will be commanded by a complex control system based on a programme series selected by patient, depending on or / and by direct picking and processing of biosignals he emitted.

The necessity of the realization of some multipurpose equipments that can be developed in the future like some complex equipment, allowing disabilitated patients movement in various situations: escalating stairs, climbing into the transport vehicles, vertical chair adjustment, goning up and down from public transportation system, going around obstacles.

The high number of potential users around the world, and especially those from our country for who these equipments could be, in the same time, a very important way for increasing their life quality.

The opportunities for important scientific and technical progresses from the electronic area, informatics area and robotic area (especially in the last two decads), make possible and in the same time necessary, the realization of some very complex equipments, that have high performances and miniaturization;

To reduce the social cost that are very high (and continue to increase in civilized countries) for social-professional integration of the affected persons;

To increase the comfort and safety of the patient; in Romania is not made a similar equipment of transportation which to allow the safety movement of the persons with locomotory problems; these devices don’t allow ortostatism and going from “suspended”, passive or only on band – not on real area – not being in this way a solution for the problem;

The anthropoid robotics recorded, in the last three years, impressive progresses in known centres from developed countries (Japan, USA, Germany), finally succeeded to realize biped robots having almost human-like performances in orthostatism, walking, active balance and straightenings. They even realized robotic orthesis which allow walking to disabilitated person, although not aesthetics and quite incomfortable for user(large dimensions and weights for drives, incomfortable equipment annexes, low energetic authonomy etc.)


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4. REQUIREMENTS • To be made of easy structure: aluminium,

composite, etc.; • The wheel chair structure allow its modulation

for offering the possibility of different groups of patients to use it;

• Easy movement without risks or areas of jam of the wheel chair structure compoentes;

• Safety of the system for fixing the wheel chair structure components;

• To allow the wheel chair folding for reducing its dimensions for transportation;

• To allow the placement of the lifting devices for changing the wheels.

• To allow lifting of the wheel chair and of the persons from wheel chair for going through narrow places;

• The lifting device must be part of the hand power wheel chair structure.

5. GENERAL PRESENTATION The experimental models of wheel chairs offer safety, mobility, accessibility and comfort taking in consideration that the patient need the wheel hair every day, increasing the level of personal autonomy. Are developed two conceptual models: Integrated conceptual model of a hand power wheel chair materialized by the realization of some components of the structure like: hand power wheel chair structure, lifting device and ways of driving, detachable wheels. The structure of the wheel chair is made of composite materials (flexible) and allows: The folding of the wheel chair for reducing the

weight; The placement of the lifting elements for

changing the wheels; The placement of some damping elements; The lifting device is a new element that allows

the wheelchair lifting for detaching the wheels, for crossing the narrow places.

The lifting device is a part of the wheelchair structure and is made of: bolt and nut and telescopic bar, being mounted in the wheelchair structure in the back part, having as function the lifting of the wheelchair and of the patient that use the wheelchair.

The detachable wheels of the wheelchair allow the wheelchair to pass the narrow places.

The function of the detachable wheel is to drive the wheelchair by manual power and to create the possibility of disassembly by the person that is in the wheelchair after the wheelchair was lift by the lifting device.

Integrated conceptual model of the electric power wheel chair materialized by realization

of some components of the structure like: electric power wheelchair structure, vertical lifting device, driving detachable wheels.

6. RESULTS AND DISCUSSIONS Based on the studies made by the consortium partners was elaborated a technical synthesis stadium and it was made the design, the manufacturing and the experimentation of a integrated conceptual model of a wheelchair, by the manufacturing of some components that are part of the wheelchair structure, like: - Wheelchair structure, - Wheelchair lifting device and solutions for

actuation, - Detachable wheels. - The structure is made of composite materials

(modular structure): - Allows the wheelchair folding and unfolding

for weight decreasing, - Allows the emplacement of the wheelchair

lifting elements for detaching the wheels, - Allows the emplacement of some damping

elements that take the shocks during moving, - The using of some dimensions that allow the

overall size adjustment.

Fig. 1 - Wheelchair – prototype

The lifting device is a new element that allows the wheelchair lifting for detaching the wheels, for crossing the narrow places.

Fig. 2 - Lifting device Fig. 3 - Lifting device –

detail view


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The lifting device is a part of the wheelchair structure and is made of: DC electric engine, Bolt and nut, Telescopic bar. It is mounted in the wheelchair structure in the back part, having as function the lifting of the wheelchair and of the patient that use the wheelchair.

Fig. 5 - Detachable wheel

with hand power

Fig. 6 - Detachable driving wheel

The detachable wheels of the wheelchair allow the wheelchair to pass the narrow places. The wheel felly of made of a special bearing that carry out the demands of exploitation, speed, easy disassembly of the wheel by the persons that is in the wheelchair. The function of the detachable wheel is to drive the wheelchair by manual and electric power and to create the possibility of disassembly by the person that is in the wheelchair after the wheelchair was lift by the lifting device. The wheel can be disassembly from the wheelchair structure. Main characteristics: - Total width of the wheelchair (with the wheels

on the wheelchair) 660 mm; - The height of the seat area in regard to the

ground 450 mm; - Total height of the wheelchair 920 mm; - Wheels diameter φ 560 mm; - Wheelchair width (with wheels detached and

hand break assembly swing over) 480 mm; - Total lift of the lifting device c = 65 mm; - Total lift of the wheelchair cr = 20 mm; - Total length of the wheelchair L = 1090 mm; - The diameter of the swivel front wheel Dpiv =

140 mm; - The diameter of the oscillatory posterior wheel

Dosc = 100 mm;

3. CONCLUSIONS The researches made in this project had as main objective the conceptual development of some integrated, complex, competitive models of complex equipments which to carry out the problems of the persons with a high degree of disabilitation for reducing their psychological impact and for their socio-economic integration, in general by offering them a means of independent transportation and the realization of the experimental models of some wheel chairs, that are hand power or electric power, with modular and flexible structures, with a high degree of flexibility. The experimental models of the components and the wheelchair are the realization of the projects elaborated and had as main target the realization of a way of transport design for persons with disabilities. The components that are part of the electric and hand power wheelchair can be developed as individual products with high performances, being able to be used to the realization of new products for persons with disabilities. Based on the conceptual models can be developed in the future a wide range of similar equipments, with simple or complex functions, hand power or driven by other means, fix, foldable, with special accessories, with flexibility possibilities according to the disabilitation degree, for offering safety to the persons with neuro-kinetic deficiencies. REFERENCES [1] Project “DITEH” – Contract 191/2006 – developed between 2006-2008 within CEEX National Program – Viasan. For more information, please see – http://www.ictcm.ro/Ceex2006/diteh/index.html [2] Dubey G.K., ”Power Semiconductor Controlled Drives”, Prentice-Hall, Inc., 1989; [3] Fransua Al., Măgureanu R. ”Maşini şi acţionări electrice”, Ed. Tehnică, 1986; [4] Năvrăpescu V., Popescu M., Covrig M., “Acţionări Electrice de Curent Continuu”, Ed. ICPE 1999.


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METODE MODERNE DE STUDIU A NANOCOMPOZITELOR

Carmen Răducanu, Gabriela Diacov, Dumitru Bucă, Roxana Neagu, Mihaela Hrişcu

SC ICTCM Institutul de Cercetare si Proiectare Tehnologica pentru Constructia de Masini SA Bucuresti, ROMANIA

E-mail: [email protected]

REZUMAT Articolul oferă cele mai recente informaţii privind sistemele de înaltă rezoluţie, microscopice. Au fost studiate mai multe metode cu privire la vizualizarea structurii nanocompozitelor electrodepuse: TEM (Microscopul electronic cu transmisie), SEM (Microscopul electronic cu scanare), AFM-( Microscopul de forta atomic), STM (Microscopia tunel cu baleiaj). Impreuna cu bază de date tehnice, de hârtie, de asemenea, prezinta imagini tipice pentru metodele de studiu implicate.

ABSTRACT The paper offers the most recent information on high resolution microscopic systems. There have been studied several methods concerning the visualization of the structure of electrodeposisits nanocomposites: TEM (Transmision Electron Microscope), SEM (Scanning Electron Microscope), AFM- (Atomic Force Microscope), STM (Scanning Tunelling Microscope). Toghether with basic technical data, the paper also presents typical images for the involved studying methods. CUVINTE CHEIE: nanotehnologii, nanocompozite, difractie de raze X, spectroscopie de raze X, absorbtie atomica KEYWORDS: Nanotechnologies, nanocomposites, X-ray diffraction, X-ray spectroscopy, atomic absorption 1. INTRODUCERE

Exista ramuri ale industriei unde se

impune folosirea unor materiale cu proprietati speciale, de aici apare necesitatea realizarii de noi materiale cu proprietati performante sau imbunatatirea celor existente. Deasemeni din punct de vedere ecologic se impune gasirea unor noi tipuri de materiale care sa incetineasca ritmul de consumare a rezervelor naturale ale Terrei.

Domeniul nanotehnologiilor s-a impus ca domeniul cu cea mai mare actualitate, cu cea mai mare dinamica si cu un impact revolutionar asupra industriei si societatii pentru urmatoarele decenii.

Nanotehnologiile permit intelegerea, controlarea si manipularea materiei la nivelul atomilor, moleculelor si al ciorchinilor de molecule cu dimensiuni pana la 100 diametre moleculare.

Nanomaterialele cele mai noi materiale in

“voga” la inceputul secolului XXI sunt acele materiale care se caracterizează prin dimensiuni foarte mici, nanometrice ale granulaţiei. Structurile nanometrice nu numai că sunt foarte mici, ajungându-se chiar până la scara atomică, dar ele posedă unele proprietăţi total deosebite şi neaşteptate, în comparaţie cu aceeaşi substanţă luată la nivel macroscopic.

Caracterizarea nanomaterialelor se realizeaza cu ajutorul tehnicilor analitice moderne (microsonda electronica, microscop electronic, difractie de raze X, spectroscopie de emisie optica, spectroscopie de raze X, absorbtie atomica, etc.).


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2. TEHNICI MICROSCOPICE

- Microscopul electronic cu transmisie, cunoscut in literatura de specialitate sub prescurtarea de TEM (Transmision Electron Microscope). Microscopia electronică cu transmisie implica o rază de electroni la tensiune înaltă emisă de un catod, de regulă filament de tungsten, şi focalizată de lentile electrostatice şi electromagnetice. Raza de electroni care a fost transmisă printr-un specimen parţial transparent pentru electroni transportă informaţie despre structura internă a specimenului în raza care ajunge la sistemul de formare a imaginii. Variaţia spaţială a acestei informaţii ("imaginea") este apoi mărită de o serie de lentile electromagnetice până când este înregistrată la coliziunea cu un ecran fluorescent, placă fotografică, sau senzor de lumină cum ar fi un senzor CCD. Imaginea detectată de CCD poate fi afişată în timp real pe un monitor sau transmisă pe loc unui calculator.

Rezoluţia unui microscop electronic cu transmisie este limitată în principal de aberaţia de sfericitate, dar o nouă generaţie de sisteme de corecţie a aberaţiilor a avut ca efect depăşirea parţială a aberaţiilor sferice şi creşterea rezoluţiilor. Corecţiile din software ale aberaţiei de sfericitate pentru microscoapele electronice cu transmisie de înaltă rezoluţie a permis producerea unor imagini cu rezoluţie suficient de bună pentru a evidenţia atomi de carbon în diamante, aflaţi la distanţe de doar 0.89 ångströmi (89 picometri) unii de alţii şi atomi din silicon la distanţe de 0.78 ångströmi (78 picometri), mărind de 50 de milioane de ori.

Fig.1. Schema de principiu a microscopului electronic prin transmisie:

a – regim de formare a imaginii; b – regim de microdifracţie; 1 – sursă de electroni; 2 – lentilă-condensor; 3 – obiect; 4 – lentilă-obiectiv; 5 – diafragmă colectoare; 6 – lentilă intermediară; 7 – lentilă de proiectare; 8 – ecran fluorescent sau placă fotografică

În TEM contrastul imaginii este condiţionat

de intensitatea undelor asociate electronilor reflectaţi conform legii lui Bragg, pe diferite sectoare ale probei-folie de studiu. Cu ajutorul diafragmei apertură a lentilei obiectiv electronii reflectaţi sunt reţinuţi şi acestea nu participă la formarea imaginii. În acest caz imaginea este formată numai de fasciculul direct şi de elec-tronii împrăştiaţi neelastic la unghiuri mici. Această formă de reprezentare a imaginii se numeşte imagine în cîmp luminos,iar contrastul – prin difracţie.

Dacă prin înclinaţia sistemului de iluminare sau prin deplasarea respectivă a diafragmei apertură,fasciculul difractat (reflectat conform legii lui Bragg) este dirijat pe axa lentilei obiec-tiv, atunci imaginea obiectului va fi formată de razele reflectate. Aşa formă de reprezentare a imaginii se numeşte imagine în cîmp întunecat.

Obţinerea în TEM a imaginilor în cîmp luminos şi în cîmp întunecat se completează una pe alta şi permite a judeca cu o mare certitudine despre microstructura obiectului studiat.

În TEM poate fi obţinut tabloul de difracţie de la sectoarele mici ale obiectului – microdifractograma. Pentru aceasta trebuie de micşorat puterea optică a lentilei intermediare şi de făcut posibil ca planul focal posterior al lentilei obiectiv să fie focalizat pe ecran. În acest caz pe ecran se va observa tabloul de difracţie a electronilor de la sectorul translucid al probei, plasată în planul de formare a primei imagini intermediare ( fig.1 mersul razelor în TEM în regimul microdifracţiei).

Obţinînd microdifractograma, se poate de legat particularităţile structurii probei, evidenţiate pe microfotografie, cu cristalografia acesteia. Afară de aceasta, microdifractograma poate fi utilizată pentru identificarea fazelor în proba cu structură eterogenă.

- Microscopul electronic cu scanare sau baleiere cunoscut in literatura de specialitate subprescurtarea de SEM (Scanning Electron Microscope) microscopul electronic cu scanare[ produce imagini prin detecţia electronilor secundari, cu energie scăzută, emisi de pe suprafaţa


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specimenului datorită excitării acestuia de către raza principală de electroni. La interacţiunea fasciculului de electroni cu proba - ţintă apar numeroase efecte fizice care servesc ca surse de diverse tipuri de semnale. La ele se referă radiaţia X, catodoluminiscenţa, electronii reflectaţi, absorbiţi, secundari, transmişi şi Auger, curentul indus de sonda electronică şi tensiunea electromotoare indusă de sarcină. Semnalele formate de detectoarele respective se amplifică şi se utilizează la dirijarea strălucirii ecranului tubului catodic (TC). Pentru fiecare punct al probei există un punct pe ecranul l TC strălucirea căruia este condiţionată de semnalul detectorului obţinut ca rezultat al interacţiei sondei electronice cu proba.

Dacă interacţia ar fi aceeaşi în toate punctele probei, atunci pe ecranul TC ar fi o strălucire uniformă, în realitate, din cauza variaţiei proprietăţilor locale ale probei, interacţia fasciculului electronic în diferite locuri ale probei este diferită.Dacă în două puncte P1 şi P2 semnalul S este diferit după valoare, atunci spunem că există contrast între imaginile acestor puncte, iar măsura contrastului este mărimea

1 2 / / ,med medC S S S S S= − = ∆ (1)

- unde S1 şi S2 sunt semnalele în punctele 1 şi 2; Smed este nivelul semnalului mediat pentru toate punctele.

Asupra caracterului de interacţie al fascicului cu proba pot influenţa topografia, componenţa chimică, structura cristalină, cîmpul electric şi magnetic şi alte proprietăţi ale probei.

Deoarece caracterul de interacţie variază de la un punct la alt punct al suprafeţei probei semnalele formate de detectori, prin urmare şi strălucirea punc-telor respective pe ecranul TC, de asemenea vor varia. Asupra formării imaginii influenţează fiecare semnal de interacţie al electronilor cu proba. Aceste semnale în microscopia electronică cu baleiaj se utilizează pentru obţinerea informaţiei despre componenţa calitativă şi cantitativă a substanţei, despre proprietăţile fizice, fizico – chimice şi cristalochimice ale acesteia. Unele semnale (emisia electronică secundară, catodolu-miniscenţa, curentul indus de sonda electronică) se uti-lizează pentru studiul dispozitivelor cu semiconductori în regimurile static şi dinamic.

Principiul de funcţionare a SEM este prezentat în schema - bloc din fig.2 Fasciculul de electroni este format de tunul electronic 1. La ieşirea din tunul electronic diametrul minim al fasciculului, în cazul utilizării catodului de volfram de forma săgeţii (termoemitor), constituie aproximativ 10 µm, iar în cazul utilizării emiterului autoelectronic (de forma unui ac) - mai puţin de 10 µm.

Apoi fasciculul electronic cu energia în intervalul 0,1 – 50 keV (în dependenţă de tensiunea acceleratoare) este focalizat cu una dintre cele două lentile condensor 2, este deflectat în rastru cu ajutorul a două perechi de bobine deviatoare 3, prin care de la un generator 4 se avansează curent în formă de dinţi de ferestrău şi în cele din urmă este focalizat în forma de sondă de diametru mic (de obicei mai mic de 10 nm) pe proba 6 de către lentila obiectiv 5. Imaginea obiectului va fi obţinută în regimul electronilor secundari 7 sau cu ajutorul electronilor incidenţi reflectaţi 8.

Electronii secundari smulşi din probă sau electronii incidenţi reflectaţi nimeresc în cîmpul electric al colectorilor 13 şi 14 respectiv şi sunt captaţi de aceştia. Fiind amplificat de amplificatorul 21, videosemnalul este avansat la modulatorul TC 22 cu o deflectare sincronă a fasciculului de către bobinele deviatoare 3 alimentate cu curent de la generatorul 4.

Semnalul video în prealabil (pînă la avansarea la TC) poate fi prelucrat de un dispozitiv videocontrol al SEM pentru majorarea raportului semnal/zgomot al contrastului imaginii, înregistrarea cadrului etc. În SEM moderne dirijarea fasciculului se realizează cu ajutorul computerului. Sonda electronică, fiind fixată pe o durată mică de timp, pe o regiune mică a suprafeţei probei, prin salt este deplasată pe o altă regiune. Particularitatea caracteristică a imaginilor obţinute în SEM, în comparaţie cu cele optice, este marea adîncime a clarităţii: aproximativ cu două ordine de mărime mai mare decît într-un microscop optic obişnuit. Acest efect "pozitiv" este condiţionat de cel "negativ" - de marea aberaţie sferică a lentilelor electromagnetice, care micşorează apertura unghiulară a fasciculului electronic.

Fig. 2. Schema-bloc a coloanei şi formarea

imaginii în SEM:


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1 – tun electronic; 2 – lentile-condensor; 3 – bobine deviatoare; 4 – generator de deflectare; 5 – lentilă-obiectiv; 6 – probă; 7 – electroni secundari; 8 – electroni primari reflectaţi; 9 – electroni transmişi; 10 – electroni absorbiţi; 11 – luminiscenţă catodică; 12 – radiaţie X; 13, 14, 15 – detectori de electroni secundari, primari reflectaţi şi de radiaţie X; 16 – detector de TEM indusă de sarcină; 17 – rezonator de ultraînaltă frecvenţă; 18 – înregistrator DLTS; 19 – piezotransformator; 20 – fotomultiplicator; 21 – videoamplificator; 22 – tub catodic

Formarea imaginii în SEM "punct cu punct"

(dimensiunea "punctului" aproximativ corespunde diametrului sondei electronice pe probă) esenţial simplifică interpretarea imaginilor obţinute în acesta faţă de cele obţinute în TEM , care se formează, practic, în acelaşi moment cu interferenţa fasciculelor electronice, transmise prin diferite "puncte" ale probei. Transformarea informaţiei despre starea suprafeţei probei în cod temporal permite utilizarea diverselor metode radiotehnice la prelucrarea videosemnalului: de a îngusta sau a lărgi banda de transmisiune, de a îmbunătăţi raportul semnal/zgomot, de a realiza transformarea neliniară a semnalului (aşa-numita corecţia – Y) pentru îmbunătăţirea contrastului imaginii etc.

Datorită acestor particularităţi de obţinere a videosemnalului şi de formare a imaginii SEM au o largă utilizare în diverse domenii ale ştiinţei şi tehnicii contemporane.

Una dintre importantele performanţe ale SEM reprezintă numeroasele moduri de obţinere a informaţiei despre probă, fiind rezultatul varietăţilor mecanismelor fizice de interacţie a fasciculului electronic cu corpul solid (fig.2).

În SEM raza de electroni parcurge întreg specimenul, detectorii construind o imagine prin maparea semnalelor detectate la poziţia razei. În general, rezoluţia TEM este de regulă cu un ordin de mărime mai mare decât cea a SEM, dar, datorită faptului ca imaginea produsă de microscoapele cu scanare se bazează pe procese de suprafaţă şi nu pe transmisie, este capabil să vizualizeze probe mai mari, şi are o adâncime de penetrare mult mai mare, producând astfel imagini care sunt o bună reprezentare tridimensională a probei.

- Microscopul de forta atomic (Atomic Force Microscope - AFM) a deschis noi perspective in analiza structurii intime a materialelor. Metoda se bazeaza pe forta de respingere care ia nastere intre varful dispozitivului de explorare si suprafata care se examineaza. Ori de cate ori aceste suprafete sunt mai apropiate decat o anumita distant critica, ele se resping.

Densitatea de current ramane neschimbata, deoarece intre suprafata probei si varful dispozitivului de explorare nu se inchide nici un circuit electric. Forta de respingere este de aproximativ 10-6…10-8N, astfel incat, practice, nici chiar o suprafata foarte moale nu presupune restrictii.

Fig. 3. Principiul de functionare al unui microscop AFM

1-un cantilver prevăzut cu un vârf ascuţit; 2- un scanner care controlează poziţionarea pe axele x-y-z; 3-un laser cu semiconductor; 4-un fotodetector; 5- circuit de control al reacţiei .

Sonda microscopului cu forta atomica este

alcatuita dintr-o lamela sub forma de cruce, alungita si elastica, numita cantilever, cu dimensiuni de ordinul zecilor de microni, în capatul careia este plasat un ac ascutit, perpendicular pe cantilever. Cantileverul este miscat în plan xy si vertical de un sistem de pozitionare piezoelectric, cu precizia în jur de 5 nm orizontal si pâna la 10 pm vertical. În timp ce acul baleiaza suprafata, miscându-se în sus si în jos odata cu conturul acesteia, o raza laser cade oblic pe partea superioara (puternic reflectatoare) a cantileverului si se reflecta catre un senzor alcatuit din doua fotodiode alaturate. Diferenta dintre semnalele celor doua diode indica pozitia spotului laser pe senzor si deci pozitia pe verticala a cantileverului. Deoarece distanta între cantilever si detector este de obicei de mii de ori mai mare decât lungimea cantileverului, sistemul realizeaza o marire a deplasarii cu un factor de peste 2000, usor de masurat.

4

5

2

3

1

5


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Acul cu un varf foarte ascutit (in varf se afla cativa atomi), montat pe cantilever se deplasează pe suprafaţa probei după un rastru de baleiaj. Vârful acului face ca latura cantilverului care îl conţine sa se deformeze in funcţie de forţele care actioneaza asupra sa . Aceste forte sunt intr-o stricta relaţie cu harta topografica a probei studiate. Vârful este apropiat de proba pana când intre acesta si molecule din proba se stabileşte o forta din categoria fortelor van der Waals, bazate in primul rand pe fortele electrostatice dintre particulele incarcate ale acului si probei. Aceasta forta, in funcţie de “denivelările” de la suprafaţa probei , respinge sau atrage vârful . Cantileverul sesizează aceste deplasări pe axa z , si in baza lor , alături de ofsetul (x,y) căruia ii este asociata forta care actioneaza asupra vârfului pe axa z , unitatea de calcul asociata microscopului cu forte atomice poate alcătui a harta topografica a probei. In timp ce cantileverul de deformează, lumina provenita de la un laser este reflectata pe o fotodioda splitata. Măsurând diferenţa de semnal (A-B) , deformările cantilverului pe axa z pot fi observate si măsurate foarte precis. Din moment ce cantileverul respecta legea lui Hooke pentru mici deplasamente , se regaseste o forta de interactie intre vârf si proba . Deplasarea vârfului sau a probei este realizata cu ajutorul unui dispozitiv de poziţionare deosebit de precis realizat din ceramici piezo-electrice, cel mai adesea sub forma unui scanner tub. Scanner-ul este capabil de rezoluţii sub nivelul unui Angstrom pe direcţiile axelor x,y si z. In mod convenţional , axa z , este perpendiculara pe proba. Mecanismul de detectie a semnalului sondei, actioneaza asupra circuitului de reactie, care la randul sau actioneaza asupra traductorului piezoelectric ce actioneaza intr-un mod foarte fin asupra suportului probei, in functie de modul de lucru dorit.

Cand AFM opereaza in aer, umiditatea mediului ambient poate crea o forta de atractie vascoasa, inconvenient care dispare atunci cand se opereaza in mediu lichid sau vid. Vidul permite cresterea factorului de calitate (Q factor) a oscilatiilor cantileverului care, la randul sau, isi imbunatateste considerabil sensibilitatea la masurarea fortelor magnetice slabe intre varf si proba. Avantajul vidului consta in simplitatea lui in utilizare si timpul scurt necesar pentru pornire. Sistemele de vid inalt si ultra-inalt ofera puritatea necesara a proceselor.

In sistemul AFM se poate observa si topografia suprafetelor neconductoare, ceea ce nu este posibil prin microscopie electronic de emisie. Metoda este indicate, de asemenea, in investigarea depunerilor organice, precum si a fenomenelor de coroziune. Pentru analiza compozitiei chimice a straturilor superficiala a materialelor se foloseste o tehnica numita spectrometria de electroni Auger.

Masurarile electrochimice permit obtinerea de imagini SPM a suprafetei cu rezolutie atomica, studii de depunere si observare a substantelor de pe suprafata probelor cu controlul puritatii sistemului proba-electrolit. Noua celula electrochimica este universala si capabila sa efectueze experimente AFM si STM cu incalzirea/racirea probei in domeniul -10 to + 60°C.

-Microscopia tunel cu baleiaj (MTB) a

fost fondată în anul 1981 de către laureaţii premiului Nobel G. Binnig şi G. Rohrer. Ea oferă posibilitatea de a analiza atom cu atom, adică de a traversa periodic rînd cu rînd întregul sector supus examinării al obiectului de studiu. Astfel s-au realizat progrese în vederea cunoaşterii lumii atomilor separaţi în orice substanţă fără a o distruge.

Principiul de funcţionare al MTB comparativ este simplu: către suprafaţa de studiu se apropie un ac pînă cînd între probă şi ac nu se va crea un curent de tunel (fig. 4). Cu ajutorul computerului se dirijează deplasarea acului, menţinîndu-se constantă distanţa ac - probă sau curentul de tunel. Raza de curbură a vîrfului ascuţit (de obicei din volfram) este mai mică de 1000 Å, spaţiul de lucru (de la vîrful acului pînă la suprafaţa examinată a probei) este de circa 3 Å, tensiunea de lucru între ac şi probă este aproximativ de 0,1... 10 V, curentul de tunel, de obicei, se află în limitele 0,1... 10 nA şi variază aproximativ cu ordinul de mărime la variaţia spaţiului de lucru cu 1 Å.

Fig. 4 . Schema-bloc a MTB:

1 – probă; 2 – ac; 3 – computer; 4, 5, 6 – convertizoare analoge-digitale


34

Curentul de tunel în fond "cordonă" între cei mai apropiaţi atomi ai acului şi probei, fapt ce conduce la o rezoluţie a MTB "pe orizontală" (în planul suprafeţei examinate) de ordinul l dimensiunilor atomice – circa 1 Å.

Datorită dependenţei exponenţiale a probabilităţii de tunelare de distanţa ac-probă r

( ) 0exp 2 / 2 ,W r m U = − ⋅ h (2)

Unde: m0 – masa electronului; h – constanta lui Planck; U – înălţimea barierei de potenţial, rezoluţia MTB "pe verticală" atinge 10-2 Å. Deci, cu ajutorul acestui aparat se poate localiza un volum de aproximativ 10-2 Å 3.

Inventarea microscopului tunel cu baleiaj a lărgit esenţial limitele de utilizare a microscopiei cu baleiaj. Din punctul de vedere al aplicaţiilor în domeniul fizicii corpului solid şi al microelectronicii cu semiconductori MTB prezintă interes prin faptul că posedă un înalt grad de rezoluţie (pînă la 1 Å) şi poate funcţiona atît în vid cît şi în medii lichide şi gazoase, inclusiv poate servi drept sursă de informaţie despre microrelieful suprafeţei examinate, spectrele stărilorr electronice, investigarea proceselor de creştere a peliculelor şi de generare a defectelor etc.

Acest aparat poate fi combinat cu SEM astfel încît ambele se completează unul pe altul. Dacă MTB se utilizează nu în regimul curentului de tunel, ci în regimul emisiei autoelectronice, atunci acesta poate fi transformat într-un analog al SEM cu energii mici ale fasciculului: la energia de 15 eV rezoluţia unui astfel de "SEM fără lentile" este aproximativ de 30 Å. Pot fi studiate de asemenea oscilaţiile curentului ce apar în spaţiul ac-probă, fiind similare cu undele electronice staţionare, emisia fotonilor, mecanismele de excitare ale plasmonilor etc.

MTB face posibilă trasarea desenelor în diapazonul de dimensiuni nanometrice, adică crearea nanotehnologiei.

3. ALTE TEHNICI DE

INVESTIGARE

3.1. DIFRACTIA DE RAZE X

Scopul urmarit de analiza calitativa a fazelor prin metoda de difractie cu radiatii X, consta in stabilirea componentelor cu structura cristalina distincta prezente in proba studiata si a proportiilor fazelor componente ale aliajului din care este constituita proba.

Metoda curent folosita astazi pentru analiza structurala calitativa consta in compararea datelor structurale extrase din spectrul de difractie al probei investigate cu cele caracteristice diferitelor substante ( faze, compusi ) cristaline cunoscute. Datele structurale necesare compararii sunt luate din fisele ASTM.

Identificarea naturii fazei se face tinand cont de pozitionarea liniilor de difractie respectiv de distantele interplanare dhkl asociate maximelor de difractie prin relatia Bragg.

Fig. 5 . Difracţia de raze X

2sin

nd λθ

= (3)

Unde: λ este lungimea de undă a radiaţiei X, n este ordinul difracţiei, θ este unghiul de difracţie.

Difracţia are loc dacă este îndeplinită relaţia de mai sus. Aceasta se îndeplineşte dacă se variază în mod continuu lungimea de undă sau unghiul sub care este iradiată proba, într-o gamă de valori.

Folosind aceste principii s-au dezvoltat mai multe metode experimentale de studiu al materialelor cu raze X: metoda Laue (folosită în special pentru a determina orientarea unor cristale mari, fixe, iradiate cu o undă cu un spectru mai larg de lungimi de undă), metoda cristalului rotitor (sursă monocromatică de raze X şi un cristal montat cu o axă normală la raza incidentă) şi metoda pulberilor (folosită pentru determinarea cu acurateţe a parametrilor reţelei).

In acest sens succesiunea de linii de difractie ale unei substante, respectiv succesiunea de distante interplanare atribuite din fisierul ASTM se compara cu cele gasite diagrama de difractie.

Sistemul de fise ASTM pentru indexarea compusilor, fazelor anorganice contine difractogramele complete a cca. 50.000 de compusi si fazele anorganice, date fiecare sub forma de tabel. Fiecare tabel contine: distantele interplanare in ordine descrescatoare, indicii Miler ai fazei si intensitatea relativa a maximului in raport cu cel mai intens maxim.


35

In consecinta imaginea de difractie (spectrul

de difractie) a unui compus sau a oricarei faze cristaline este data de structura sa cristalina spatiala (aranjamentul spatial al atomilor lor), proprie si neambigua pentru faza respectiva, la fel ca o amprenta digitala. Difractia de raze X, fiind o metoda nedistructiva si care nu necesita contact direct cu proba studiata, este ideala pentru studiile “in situ”.

3.2. ANALIZA SPECTRALA Tranzitia unui atom intre doua nivele

energetice observata cu un aparat spectral este pusa in evidenta sub forma unei linii spectrale.

Linia spectrala este caracterizata prin valoarea frecventei radiatiei monocromatice (sau numarului de unda). Fiecare specie de atomi sau molecule poate fi identificata prin studierea nivelelor energetice specifice. Energia emisa sau absorbita ca urmare a tranzitiilor intre aceste nivele este caracteristica fiecarei specii in parte. Masurarea intensitatii liniilor spectrale da informatii cantitative despre speciile ce emit respectivele linii.

Pozitia liniilor spectrale in spectru da informatii calitative despre esantionul studiat; marimea intensitatilor acestor linii da informatii cantitative despre componentii esantionului analizat.

3.3. SPECTROMETRIA DE FLUORESCENTA DE RAZE X

Analiza prin spectrometria de fluorescenţă cu

radiaţii X este considerată ca fiind una dintre cele mai evoluate metode instrumentale de stabilire a compoziţiei chimice a unei probe.

Metodele de analiză bazate pe spectrometria de radiaţii X au la bază fenomenele fizice produse la interacţiunea radiaţiilor X cu substanţa. În funcţie de aceste fenomene, metodele pot fi clasificate în metode de emisie, metode de absorbţie, metode de difracţie etc.

Fluorescenţa de radiaţii X are la bază emisia de radiaţii X, atunci când se utilizează ca sursă pentru excitarea emisiei secundare de radiaţii X un fascicul incident (primar) de radiaţii X. Această metodă se foloseşte pentru analiza elementală calitativă şi cantitativă a unei probe.

Principiul fizic al metodei: un fascicul de radiaţii X de mare intensitate (fascicul primar) care ajunge pe probă produce o excitare a atomilor acesteia; revenirea atomilor excitaţi în starea fundamentală se realizează prin emisie de radiaţii X caracteristice; această emisie de radiaţii X caracteristice se numeşte radiaţie de fluorescenţă sau emisie secundară de radiaţii X si este caracteristica fiecarui element chimic.

Fluorescenţa de radiaţii X (XRF- X-Ray Fluorescence) permite determinarea elementelor chimice dintr-o probă, având o limită de detecţie de ordinul zecimilor de ppm.

În spectrometria de radiaţii X se folosesc două metode de analiză a radiaţiei de fluorescenţă: - Metoda dispersiei radiaţiilor X după lungimea de undă (WDXRF-Wave Dispersive X-Ray Fluorescence); se bazează pe determinarea lungimilor de undă a radiaţiilor de fluorescenţă cu ajutorul cristalelor analizoare şi măsurarea intensităţii în funcţie de lungimea de undă. Prin această metodă se poate realiza analiza calitativă a unei probe prin identificarea liniilor de emisie principale ale seriilor K şi L pentru elementele componente din probă. - Metoda dispersiei radiaţiilor X după energie (EDXRF-Energy Dispersive X-Ray Fluorescence). se bazează pe măsurarea energiei radiaţiilor X de fluorescenţă. Aceată metodă permite obţinerea unor valori mai mari ale intensităţii radiaţiilor de fluorescenţă, deoarece aceste radiaţii sunt măsurate direct cu ajutorul unor detectoare semiconductoare (Si, Ge) spre deoasebire de prima metodă în care se folosesc cristale analizoare în care se produc pierderi mari ale intensităţii radiaţiilor X de fluorescenţă. În această metodă se poate realiza analiza calitativă dacă elementul determinat este prezent în probă în concentraţie de la câteva zecimi de procent până la zecimi de ppm. Confirmarea prezenţei unui element chimic în probă se bazează pe existenţa în spectru a minim două linii pentru radiaţia caracteristică a elementului chimic respectiv. Pentru efectuarea analizei cantitative este necesar să se realizeze corelarea intensităţilor liniilor de emisie măsurate cu concentraţia elementelor chimice prezente în proba analizată. Se cunosc o serie de metode care permit diminuarea sau compensarea de la dependenţa direct proporţională a intensităţii liniei de concentraţia elementului chimic: compararea cu o probă standard; trasarea curbei de etalonare; adăugarea unui standard intern; diluarea probei etc.

Fig.6. Structura de bază pentru spectrometrele

EDXRF şi WDXRF


36

Diferenţa dintre cele două categorii se află în sistemul de detecţie.

Structura de bază pentru toate spectrometrele este o sursă de radiaţii X, o probă şi un sistem de detecţie. Sursa iradiază o probă iar detectorul măsoară radiaţia provenită de la material.

Detectorul spectrometrelor EDXRF poate măsura energiile diferite ale radiaţiei caracteristice provenite direct de pe probă. Detectorul poate separa radiaţia provenită de la probă în radiaţia provenită de la elementele din probă. Această separare se numeşte dispersie.

Spectrometrele WDXRF folosesc un cristal analizator pentru dispersia diferitelor energii. Toate radiaţiile care vin de la probă cad pe cristal. Cristalul difractă energiile diferite pe direcţii diferite, similar cu o prismă ce împrăştie culori diferite pe mai multe direcţii. CONCLUZII • Domeniul nanotehnologiilor s-a impus in ultima perioada ca un domeniu de cea mai mare actualitate si cu cea mai mare dinamica; • Aparitia de noi materiale cu ajutorul nanotehnologiilor in sectoare ca: electronica, substante chimice, industria grea, industria auto, industria aeronautica si industria farmaceutica; • Caracterizarea nanomaterialelor se realizeaza cu ajutorul tehnicilor analitice moderne (microsonda electronica, microscop electronic, difractie de raze X, absorbtie atomica, spectroscopie de emisie optica, spectroscopie de raze X etc.).. • Microscopia electronica analitica obtine informatii microstructuralecantitative si calitative contribuind astfel la solutionerea unui larg domeniu de problem ale stiintei materialelor. BIBLIOGRAFIE 1. Ion Gh. Tănase, Metode instrumentale de

analiză, Partea a II-a, METODE SPECTROMETRICE, Editura Universităţii Bucureşti

2. Peter Brouwer, Theory of XRF – Getting acquainted with the principles, PANalytical BV, The Netherlands (2003)

3. René E. Van Grieken and Andrzej A. Markowicz, Handbook of X-Ray Spectrometry: Second Edition, Marcel Dekker Inc. NY (2002)

4. M.J.Armstrong and R.H.Muller, J. Electrochemical Soc.., 138, 2003

5. H.Schumann, Metallographie, 1990 6. Molecular Imaging Corporation, Catalog de

prezentare.

Quick Info Hidden Solar Cells: Three-Dimensional System Based on Optical Fiber Could Provide New Options for Photovoltaics

Converting sunlight to electricity might no longer mean large panels of photovoltaic cells atop flat surfaces like roofs.

Using zinc oxide nanostructures grown on optical fibers and coated with dye-sensitized solar cell materials, researchers at the Georgia Institute of Technology have developed a new type of three-dimensional photovoltaic system. The approach could allow PV systems to be hidden from view and located away from traditional locations such as rooftops.

“Using this technology, we can make photovoltaic generators that are foldable, concealed and mobile,” said Zhong Lin Wang, a Regents professor in the Georgia Tech School of Materials Science and Engineering. “Optical fiber could conduct sunlight into a building’s walls where the nanostructures would convert it to electricity. This is truly a three dimensional solar cell.”

Details of the research were published in the early view of the journal Angewandte Chemie International on October 22. The work was sponsored by the Defense Advanced Research Projects Agency (DARPA), the KAUST Global Research Partnership and the National Science Foundation (NSF).

Dye-sensitized solar cells use a photochemical system to generate electricity. They are inexpensive to manufacture, flexible and mechanically robust, but their tradeoff for lower cost is conversion efficiency lower than that of silicon-based cells. But using nanostructure arrays to increase the surface area available to convert light could help reduce the efficiency disadvantage, while giving architects and designers new options for incorporating PV into buildings, vehicles and even military equipment. (source: [email protected] / http://gtresearchnews.gatech.edu/newsrelease/3d-pv.htm)


37

THEORETICAL CONSIDERATION REGARDING THE DYNAMIC BEHAVIOUR OF A MODULAR SYSTEM

FOR THE MILLING PROCESS

Raluca Magdalena Nita1, Nicoleta Rachieru2

1University Politechnica of Bucharest, SC ICTCM SA, e-mail [email protected] 2 SC ALPLAST CONF SRL, e-mail [email protected]

REZUMAT Lucrarea isi propune studiul prin metoda elemetelor finite a comportarii dinamice a unui sistem modular de fixare in timpul procesului de aschiere, prin determinarea frecventelor proprii unde performanta, fiabilitatea, rezistenta si siguranta in functionare reprezinta caracteristici fundamentale ce au o influenta deosebita asupra rezultatelor finale ale procesului de prelucrare. ABSTRACT The papers aims to study with the finite elements method the dinamic behaviour of a modular system for clamping the pieces during the cutting process, through the determination of the characteristic frequency where performance, reliability, durability and reliability in function represents the fundamental characteristics have great influence on the final results of processing process. KEYWORDS: modula system, structural analysis, FEM analysis CUVINTE CHEIE: sistem modular, analiza structura, analiza FEM

1. CAD-FEM INTERFACE. ANALISED SYSTEM MODEL. When it is necessary the mechanical analisys of the deformable structures it could be used with success the finite elements method, an aproximative calculation method. Dinamic analisys of the structures assumes determination of the characteristics frequencies, at which the structures could start resoning with important implications on the final results of the processing process. At the characteristic frequency the deformations could be greater then the static deformations, this fact creating the possibility to generate deformations greater then tha static ones. When it is analyzed a complex system, it is necessary to specify the characteritics of the contact between its component parts, the way of the contact is definiton having a great influence on the results of the simulation operation. Because the contact dependends on the elastics properties of the bodies that come into contact, by their geometry and also by the way that the forces which acted on the system are applied, it is considered to be a complex phenomen.

During forces application, the dimension, the form of the surfaces and stress distribution could be modify during the processing process. In the design stage it can be used CAD programs (Computer Aided Design). CAD file it is taken over in a preproccesor program of a MEF program. One of the most commonly used types of files used to transfer databases between programs is the file type IGES (Initial Graphics Exchange Specification), which has igs extension, which has the igs extension. [Ghionea, I, 2007] In order to achieve the simulation of the flexible fixing system behavior during the cutting procces it has been realized the experimental model usind a 3D desing software. At the based model was added a bride wich has the role to overtake the axial movement of the axel, because of the action of milling forces.[ HALDER]- fig. 1. On the axel it is executed a groovekey, having the 8x4x25 dimensions.


38

The chanel it is executed with a four teeth mill, with the cutting deep t=2mm, from 2 successive drilling, mill diameter being Ø8. Tooth advance Sd is 0.10mm/rot, and S = 0.10•4= 0,40 mm/rot. The cutting speed is beeing calculate with relation (1), were Cv reprezents the cutting constant, D mill diameter [mm], tl lenth of contact [mm], Sd tooth advance [mm/dinte], t cutting deep [mm], Z teeth number, Kv corection coefficient of the speed with the work condition.[ Picoş, C, Bohosievici, 1974].

Figure 1. 3D model of the clamping system.

vpnyd

xl

m

qv

p kztStT

DCV ⋅⋅⋅⋅⋅

⋅= (1)

From calculation Vp=2,45m/min. It can be calculated mill speed n:

min/7,971000

rotDV

n p =⋅

⋅=

π (2)

It is choosen from the machine book the value for the greater tool speed the most apropieate with the results for the calculate results. So if the processing it is realised on a FUS 22 machine it is choosen n = 100 rot/min. The determination of the tangential cutting force is done using the relation (3).

qfYd

XFx DZStCF FF −⋅⋅⋅⋅= (3)

With the values for the coefficients indicated in [Picoş, C, Bohosievici, 1974], you obtain F = 234 N. The orizontal force, respectively vertical force are calulated as procent of the tangential force: H=(0.8....0.9)F ; V=(0.4...0.6)F. For the orizontal force and respectively vertical are obtain the following values: H = 200 N; V = 120 N.

Figure 2. Groove key milling

2. THEORETICAL CONSIDERATIONS FOR DYNAMIC ANALYSIS BY FINITE ELEMENT METHOD Modal analisys it is used for the determining the characteristic frequencys and the characteriscs vibration modes for the structures or structures components. Characteristic frequencies and proper modes are important measures for structure designs wich work in a dymanic behavior because they provide informations regardind the analysed structures. The dymanic study using the finite element method of the elastic structures could be as a extension of the static analysis in problems in with it is considered the time dependence of the spatial discretised modules with finite elements. Dynamic analysis assumes the structers characterisc frequencies determination, wich can start resoning with great implication for the processing process. At the resonance frequency the analised structure deformations could be bigger then the static deformation, this fact could generate great errors in the processing process. Where determind the first four characteristic frequencies, considering them to be enough, because they grow, and if the working frequencies domain is in the first four frequencies, it can be explored till the tenth characteristic frequency. 3. GENERATING THE MATHEMATIC MODEL FOR THE FINITE ELEMETS METHOD Structure discretisation, idle the passing from the material physical content from which it is executed the structure, at the conventional model – geometric, discrete, for wich it is done the finite element analysis (FEA), represent the first step in the effectuation of a such analisys.

t

t

n


39

The discretization process is one of the real continuos structure, from geometric point of view, of the way of the forces application, of the supporting conditions, of rigidities, of the mases.

Figure 3. Discretizarea retelei

When it is done the structure meshing it is necessary to take into consideration the following aspects: maximum and minimum; elements types, number of elements: maximum and minimum; elements dimensions maximum and minimum, imposed by the structures details and the scope of the account. Thus, the infinity of points of the continuous structure can be approximated by this study, respectively by the studying of the finite amount of nodes of the meshed network of the model. The meshed structure approximates from geometric and mecanic point of view the real structure. This must be done through a network as simple and as uniform as possible of lines and (or) suprafaces. On the other hand, it is not always rational that the network to be uniform because the structure may have areas whith geometric discontinuities or mechanical (eg, points of application for the concentrated loads) or regions in which because the desired consequence, it is needed a greater volume of information - so more nodes and elements. The model was meshed in 53168 elementes and 99920 nodes. The structure is homogenuous and is presented in figure 3.

4. REZULTS REGARDING SYSTEM DYNAMIC BEHAVIOUR

Figure 4. Variation of the first 6 characteristic

frequencies

Figure 5. Total deformation - frequency 1

Detetails of “Total Deformation” Scope Geometry All Bodies Definition Type Total Deformation Mode 1 Results Frequency 640.22 HZ Minimun 0mm Maximum 105.53 MM Min Occurs EH 2315 Max Occurs Screw

Figure 6. First variation of own frequency


40

Figure 7. Total deformation at second frequency

Detetails of “Total Deformation” Scope Geometry All Bodies Definition Type Total Deformation Mode 2 Results Frequency 643.57 Hz Minimun 0mm Maximum 107.09mm Min Occurs EH 2315 Max Occurs Screw

Figure 8. Second variation of own frequency

In figure 4 it is represented the first 6 characteristic frequencies variation. The value variated from aproximatively 640Hz till 851Hz. The values for the frequencies 5 and 6 have increased much, and so the analisys for the first four frequencies offers concludent informations for the dynamic behavior of the analised processed. In fig. 5-12 are presented the system deformation for every characterist frequency.

Figure 9. Total deformation third frequency

Details of “Total Deformation” Scope Geometry All Bodies Definition Type Total Deformation Mode 3 Results Frequency 672.55 Minimun 0mm Maximum 105.08 mm Min Occurs EH 2315 Max Occurs Screw

Figure 10. Variation of own third frequency

Figure 11. Total deformation at fourth frequency

Details of “Total Deformation” Scope Geometry All Bodies Definition Type Total Deformation Mode 4 Results Frequency 678.8 Minimun 0mm Maximum 108.41 mm Min Occurs EH 2315 Max Occurs Screw

Figure 12. Variation of own fourth frequency

From the analisys can be established that the most solicitated structures and were it is inregistrated the grater deformation are the screws wich are used at the fixturing of the two brides used for clampind the processed piece.


41

5. CONCLUSIONS Dynamic analisys of the analysed deviced assumed the determination of the characteristics frequencies of the structures, frequencies at wich the structure could start resoning with great implications on the working process. At the resonance frequency the structures deformation could be bigger than the static deformation. Where determined the first four characteristic frequencies considering to be enough, because this frequencies increases, and if in the working domain it cand be findin the domain of the characteristics frequencies, it can be explored till the tenth characteristic frequence. Where analised and presented the results for the first four characteristic resoning frequencies and were identified the most solicited structures for every case. So it was demonstrated that the most solicitated structers are the two screws that are used at the fixturing of the two brides used for clampind the processed piece. REFERENCES [1] Mihailidis A, Pupaza C., Nerantzus I, Karaoglnidis G.,

Modeling and simulation of o spherical bearing mount, Annals of DAAAM for 2008 & Procidings of the 19th Internationl DAAM Symposium, ISSN 1726-9679 ISBN 978-3-901 509-68-1.

[2] Catolg elemente modulare HALDER http://www.halder-inc.com/

[3] Picoş, Const, Bohosievici, Cazimir s.a. Calculul adaosurilor de prelucrare şi al regimurilor de aşchiere. Ed.Tehnică, Bucureşti, 1974.

[4] Bathe, K.J (1990) Finite Elementen Methoden, Springer Verlag, ISBN 0-387-15602-X, Berlin.

[5] Sorohan S, Petre C.C, Programe si aplicatii cu elemente finite, Printech, Bucuresti, 2004, ISBN 973-718-005-4

[6] Ghionea Ionut, Considerations about the methodology and rezults for the finite elemenent analysis of a mechanical assembly, Proceedings of the 16th Intenational Conference on Manufacturing Systems- ICMaS, ISSN 1842-3183.

[7] Sorohan, S, Constantinescu, I, Practica modelarii si analiei cu elemente finite, Bucuresti, 2003.

[8] Zienkievicz, O, The finite element method, Heinemann, 2000, ISBN 0 7506 5049 4.

Quick Info Metal Standards for Waveguide Characterization of Materials Metal waveguide inserts can be tailored to have known scattering parameters. Rectangular-waveguide inserts that are made of non-ferromagnetic metals and are sized and shaped to function as notch filters have been conceived as reference standards for use in the rectangular- waveguide method of characterizing materials with respect to such constitutive electromagnetic properties

as permittivity and permeability. Such standards are needed for determining the accuracy of measurements used in the method, as described below.

The Metal Rectangular-Waveguide Insert is sized and shaped to fit the waveguide cross-section and to act as a band-stop filter having a notch frequency of about 9 GHz. The particular waveguide cross sectional dimensions, known in the industry as “WR-90,” are for a nominal frequency range of 8.2 to 12.4 GHz.

In this method, a specimen of a material to be characterized is cut to a prescribed size and shape and inserted in a rectangular-waveguide test fixture, wherein the specimen is irradiated with a known source signal and detectors are used to measure the signals reflected by, and transmitted through, the specimen. Scattering parameters [also known as “S” parameters (S11, S12, S21, and S22)] are computed from ratios between the transmitted and reflected signals and the source signal. Then the permeability and permittivity of the specimen material are derived from the scattering parameters. Theoretically, the technique for calculating the permeability and permittivity from the scattering parameters is exact, but the accuracy of the results depends on the accuracy of the measurements from which the scattering parameters are obtained. To determine whether the measurements are accurate, it is necessary to perform comparable measurements on reference standards, which are essentially specimens that have known scattering parameters. To be most useful, reference standards should provide the full range of scattering-parameter values that can be obtained from material specimens. Specifically, measurements of the backscattering parameter (S11) from no reflection to total reflection and of the forward-transmission parameter (S21) from no transmission to total transmission are needed. A reference standard that functions as a notch (band-stop) filter can satisfy this need because as the signal frequency is varied across the frequency range for which the filter is designed, the scattering parameters vary over the ranges of values between the extremes of total reflection and total transmission. A notch-filter reference standard in the form of a rectangular-waveguide insert that has a size and shape similar to that of a material specimen is advantageous because the measurement configuration used for the


42

reference standard can be the same as that for a material specimen. Typically a specimen is a block of material that fills a waveguide cross-section but occupies only a small fraction of the length of the waveguide. A reference standard of the present type (see figure) is a metal block that fills part of a waveguide cross section and contains a slot, the long dimension of which can be chosen to tailor the notch frequency to a desired value. The scattering parameters and notch frequency can be estimated with high accuracy by use of commercially available electromagnetic-field-simulating software. The block can be fabricated to the requisite precision by wire electrical-discharge machining. In use, the accuracy of measurements is determined by comparison of (1) the scattering parameters calculated from the measurements with (2) the scattering parameters calculated by the aforementioned software.

This work was done by Kevin M. Lambert and Carol L. Kory of Analex Corp. for Glenn Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-18137-1.

(source: [email protected]) "Earth Binoculars" Sense Disasters From Space

An image from TAU's orbiting Hyperspectral Remote Sensor. (TAU) New Tel Aviv University technology combines sophisticated sensors in orbit with sensors on the ground and in the air to create a “Hyperspectral Remote Sensor” (HRS). HRS can give advance warnings about water contamination after a forest fire, or swiftly alert authorities of a pollution spill.

Professor Eyal Ben-Dor of TAU's Department of Geography describes his team’s HRS technology as a combination of physical, chemical, and optical disciplines. “When a devastating forest fire hits the Hollywood Hills, for example, we can see from space how the mineralogy of the soil has changed,” he explains. “Because of these changes, the next rainstorm may wash out all the buildings or leach contaminants into the soil. With our new tool, we can advise on how to contain the pollutants after the fire, and warn if there is a risk for landslides.”

HRS provides information useful to property developers as well. It can offer a soil profile map with detailed information for contractors, farmers, or vintners interested in making major land purchase deals or managing existing ones. It can also indicate where water runoff should be directed, and what minerals may be lacking in a given parcel of land.

About 90% of all gas stations leak contaminants into the soil, according to Ben-Dor. The HRS can monitor gas stations and identify problematic areas. “Our space sensors combined with ground measurements and GPS data will be able to detect and map hydrocarbon contamination in real time. Within a year, we’ll be able to identify these problematic areas far more quickly than with traditional methods,” he says.

The HRS simultaneously acquires hundreds of optical images, each from a different frequency, that enable a “spectral assessment” from distances high in the air via airplanes and in orbit using satellites. This raw data is then processed by the researchers to yield thematic maps.

(Tel Aviv University)

(source: [email protected])


43

STUDY OF A EHD POCKET JOURNAL BEARING

Monica Crudu *, Sorin Cananau**, Mohamad Hajjam***

*University “POLITEHNICA” Bucharest, ROMANIA, e-mail: [email protected] **University “POLITEHNICA” Bucharest, ROMANIA, e-mail: [email protected]

*** Solids Mechanics Laboratory of Poitiers University, France

REZUMAT Această lucrare cercetează efectele suprafeţelor texturate asupra unui lagăr radial ce lucrează în regim de lubrificaţie elastohidrodinamic.Regimul elastohidrodinamic implică obţinerea unor valori mult mai ridicate pentru presiunea maximă şi pentru grosimea filmului de lubrifiant îintrucât în acest caz se ţine cont şi de comportamentul elastic al materialelor. Efectele pozitive ale suprafeţelor texturate asupra creşterii portanţei şi diminuării frecărilor în ceea ce priveşte domeniul: lagărelor, etanşărilor şi a cuplei cilindru-piston sunt deja bine cunoscute. Scopul lucrării este de a determina geometria optima a unui buzunar plasat pe suprafaţa cuzinetului unui lagăr radial, geometrie ce conferă lagărului cea mai mare portanţă şi cea mai mică putere disipată. ABSTRACT

This paper deals with the textured surfaces effects of a journal bearing working in elastohydrodynamic regime. The fact that texture surfaces increase the carrying capacity and decrease the friction losses in the applications concerning the bearings, mechanical face seals and piston-cylinder couple, it’s already known. In the elastohydrodynamic lubrication regime the increase of the maximal pressure and film thickness is more accentuate that in the hydrodynamic regime because we take into account the elastic behavior of the materials. The main goal of this study is to determine the optimal pocket texture geometry, which gives the largest carrying capacity and the smallest power dissipation by geometrical modeling.

CUVINTE CHEIE: Elastohidrodinamic, Buzunar, Portanţă, Putere disipată. KEYWORDS:Elastohydrodynamic, Pocket, Carrying capacity, Power dissipation

1. INTRODUCTION

The elastohydrodynamic theory studies the influence of the elastic deformation on the bearing behavior. Many studies have revealed the positive effects of textured surfaces concerning the field of bearings, mechanical seals and piston-cylinder couple. The two modalities used for texturing are: full texturing and partial texturing. The last one it was proved to be more effective, concerning the load capacity, in mechanical face seals [2], thrust bearings [3], or thermal engines [4] .The difference is that full texturing is based on the individual dimple effect and partial texturing based on the collective effect of the dimples [5].It is also known that pocket texture performs better than partial texturing for hydrodynamic bearings [1]. This paper concerns the effect of pocket texture in elastohydrodynamic journal bearing applications.

The results from investigating the performance of bearing surfaces with rectangle pocket texture suggest that contact characteristics such as minimum film thickness, maximum pressure, axial oil film flow, may be improved through an appropriate surface texture geometry and appropriate texture localization on the contact surface. The results should reveal what is to expect from a full textured journal bearing working in a elastohydrodynamic regime.

2. THEORETICAL MODEL

To solve the problem of elastohydrodynamic regime we have to solve a system of equations consisting in:

• Reynolds equations • The law of elastic deformation of the bearing surface • The variation law of the viscosity with the pressure


44

For the simplification of the model the following assumption for elastohydrodynamic lubrication are considered valid [6]:

• The flow of the fluid is considered laminar • Static load • There are no cavitations effects • The lubricant is a Newtonian liquid • We take into account the material

comportament of the journal bearing (EHD)

Elastohydrodynamic theory, unlike classical hydrodynamic theory, takes into account the variation of the lubricant viscosity with the pressure and the elastic deformation of the film boundaries. In other words the derivation of film shape and pressure profiles for a contact thus requires a simultaneous solution of the basic lubrication and elastic equations, with a viscosity which varies along the film as the pressure alters.

Fig. 1. The theoretical model geometry

The subject of this research is the geometrical modeling of a pocket journal bearing to get:

• A maximum thickness of lubricant film • A minimal power dissipation

The geometrical modeling is performed by the software Accel, based on the Reynolds equation. The validity of the Reynolds equation when applied to pocket bearings has been confirmed in [7]. The bearing is subjected to a low load of 3000N and after at a high load of 10000N. The study concerns the influence of the pocket geometry for the two targets in the elastohydrodynamic lubrication regime. The journal bearing works at a frequency rotation of 4000 rpm and has the following geometrical configuration. We modeled one by one the three dimensions of the pocket using the range of values for the pocket dimensions described in table 3.

Table 1. Geometrical data

Diameter Width Radial clearance

Number of feeds

mm mm mm [0,10]

48 19.37 0.02 1

Table 2. Lubricant characteristics

Viscosity of

lubricant

Lubricant density

Lubricant specific

heat

Lubricant’s proportion

in the mixture

Pa.s Kg/m3 J/Kg/ºC [0-1]

0.01 900 2100 0.5

Table 3. The range of values for the dimensions of the

pocket

Circumferential length (L) Width (b) Depth (s)

◦ mm µm (0-360) (0-19.37) (3-20)

The performances of theoretical model were compared with those of the classical model of a elastohydrodynamic journal bearing and according to that comparison we obtained the final results.

3. RESULTS AND DISCUSSIONS

In the analyze of EHD lubrication regime, the thickness of the film has a very important role. Because we take into account the elastic behavior of the bearing material, we will obtain bigger values for the film thickness by comparison with HD regime. The analysis serves to quantify the evolution of the characteristics with the journal pocket texture parameters and to deduce their optimized values. The first step was the pocket width (b) modelation when the bearing is subjected to a minimal load of 3000N. The optimal value obtained for the film

F

0π 2π

L

b

s

feed

hmin

pocket pocket Sleeve


45

thickness is h = 0.006457 mm, so for b = 13.34 mm the thickness of the film increases by the reference with 2.83%. We use this value obtained for modeling the second dimension, circumferential length. The optimal value obtained is h = 0.007113 mm, so L = 210 mm increases the film thickness by the reference with 13.28%. By modeling the depth of the pocket we obtained for, s = 15 µm a gain of 46.24% in film thickness. (h = 0.009183 mm).

Fig. 2. The variation of film thickness depending on

the width of the pocket By taking the same steps we obtained a decrease of the dissipated power by the reference with 19.45%. (P = 17.43 W) for the next geometrical configuration: L=360◦; b=16.36, s =5 µm.

Fig. 3. The variation power dissipation with the

pocket depth

For the maximal load of 10000N we obtain during the same method the further diagrams for film thickness and power dissipation.

Fig. 4.The variation of film thickness depending on

the width of the pocket

The optimal value obtained is h = 0.005019 mm, so for L=210◦; b=10.34 mm; s = 10 µm on increase the thickness of the film by the reference with 52.27%.

Fig. 5. The variation of power dissipation with the pocket depth

The optimal value obtained is P = 24.55 W, so for L=210◦; b=13.34mm; s = 5 µm the power dissipated is reduced by the reference with 17.81%. The differences of the pressure distribution can be well observed at a maximal load of 10000N than at the minimal load of 3000N.

Fig. 6. The pressure distribution in a classic journal bearing

F=10000N pmax =0.2618*1.E+02MPa


46

Fig. 7. The pressure distribution in a pocket journal bearing

5. CONCLUSIONS

By combining the three optimal values of the bearing dimensions we obtain the optimal pocket geometry that give the bearing the minimal power dissipation and the maximal lubricant film thickness (table4, table5).

Table 4. The centralized results of the study for film thickness

F[N]

b[mm]

L[º]

s[µm]

[%] Gain in minimal

film thickness

3000N 13.34 210 15 19.45

10000N 10.34 210 10 17.81

Table 5. The centralized results of the study

for power dissipation

F[N]

b[mm]

L[º]

s[µm]

[%]Drop in dissipated

power

3000N 16.36 360 20 34

10000N 13.34 210 5 17.81

The positive results obtained for EHD case encourage the study of the pocket journal bearing working in real conditions, meaning dynamic charge, variable rotation frequencies etc.

REFERENCES

[1] Mihai Dobrică, Mircea Pascovici, Michel Fillon

and Traian Cicone “ Texturing effects in plane-inclined slider bearings ”, International Joint Tribology Conference, october 2007

[2] Etsion, I., Laser Surface texturing – Measure to Reduce Friction, 14th Int. Colloquium Tribology, Esslingen, Vol. I (2004), pp. 329-334

[3] Raghavendra Rao, R., Prasad, K.R. Effects of Velocity-slip and Viscosity Variation on Journal Bearings, ANZIAM Journal, 46 (2004), pp. 143-155

[4] Klingerman, Y., Shinkarenko, A.,Etsion, I.Improving Tribological Performance of Piston Rings by Partial Surface Texturing, 2004 AIMETA Conf., Rome, 2004, pp. 607-614

[5] Feldman, Y, Klingerman, Y., Etsion, I. Stiffness and Efficiency Optimization of a Hydrostatic Laser Surface Textured Gas Seal, Journal of Tribology, 129 (2007), pp. 407-410

[6] Pinkus, O., Sternlicht, B. Theory of Hydrodynamic Lubrication, McGraw-Hill, New York, 1961

[7] Dobrica, M.B., Fillon, M., 2005, “Thermohydrodynamic behavior of a Slider Pocket bearing, “ASME J. of Trib., 128, pp.312-318

[8] BLOK, H., 1959, Correlational review of theoretical and experimental data on elastohydrodynamic

[9] DOWSOND,. , and HIGGINSONG,. R., 1966, Elastohydrodynamic Lubrication (Oxford: Pergamon

Quick Info On the occasion of MEDICA 2009 fair, the global No.1 meeting point for the medical sector, ZENIT/NRW.Europa will organise in cooperation with the Healthcare Sector Group (HSG) of the Enterprise Europe Network (EEN) an international Brokerage Event, which aims at providing both the business and science sector with assistance to find partners in the countries of the Enterprise Europe Network for product development, manufacturing and licensing agreements, research co-operation, joint ventures or similar partnerships. Take this chance to:

- Use the event for international business opportunities.

- Meet providers of new technologies from all over Europe in one location.

- Get in contact with potential partners for future collaboration.

- Establish cross-border contacts for long-lasting business relationships.

The venue for the Brokerage Event is hall 6, gallery. Deadline for registration and submission of profiles is the 16 Octobber 2009. Deadline for selection of dialog partners is the 25 October 2009. Deadline for the rejection for meeting requests is the 4 November 2009. Participation fee and payment conditions: - A participation fee of 200 EUR + VAT (up to 5 profiles) will be charged to each participating organisation submitting profiles. For each profile beyond the first 5 a fee of 40 EUR + VAT will be charged. Start-ups (beginning 1.1.2007) will be granted a rebate of 50%; a copy of the certificate of registration or similar to be sent to the main organiser not later than 16 Octobber 2009, mail to:[email protected].

b=10.34 mm L=210º s=10µm pmax=0.3586*1.E+02MP


47

STUDY OF A HD POCKET JOURNAL BEARING

Monica Crudu*,Sorin Cănănău**, Aurelian Fătu***

*University “POLITEHNICA” Bucharest, ROMANIA, e-mail: [email protected] **University “POLITEHNICA” Bucharest, ROMANIA, e-mail: [email protected]

*** Solids Mechanics Laboratory of Poitiers University, France

REZUMAT Efectele pozitive ale suprafeţelor texturate asupra creşterii portanţei şi diminuării frecărilor în ceea ce priveşte domeniul: lagărelor, etanşărilor şi a cuplei cilindru-piston au fost demostrate de tot mai multe studii. Deasemenea este cunoscut şi fapul că texturarea tip buzunar comparativ cu texturarea parţială, amplifică într-o manieră mai accentuată aceste efecte în cazul lagărelor hidrodinamice[1]. Pornind de la această ipoteză, lucrarea de faţă reprezintă un prim pas în studierea efectelor texturării asupra performanţelor unui lagăr radial hidrodinamic prin evaluarea performanţelor conferite de un buzunar plasat pe suprafaţa cuzinetului acestuia. Modelând geometric cele trei dimensiuni ale buzunarului: lăţime, lungime circumferenţiala şi adâncime, se doreşte determinarea geometriei optime, ce conferă lagărului cea mai mare portaţă şi cea mai mică putere disipată.

ABSTRACT More and more studies have revealed an increase of the carrying capacity and a decrease of friction losses due to the positive effects of surface texturing concerning the field of bearings, mechanical face seals and piston-cylinder couple. Also it is well known that pocket texture amplifies this effect for hydrodynamic journal bearing more than partial texture [1]. Based on this hypothesis, this paper represents a first step in studying the texturing effects on hydrodynamic journal bearing by assessing the performances of a pocket journal bearing. The main asset of this study is to determine the optimal geometry, which gives the largest carrying capacity zone and the smallest power dissipation by geometrical modeling the three dimensions of the pocket: width, circumferential length and depth of the pocket. CUVINTE CHEIE: Hidrodinamic, Buzunar, Portanţă, Putere disipată.

KEYWORDS: Hydrodynamic, Pocket, Carrying capacity, Power dissipation .

1. INTRODUCTION

The lubrication of textured surfaces has become in recent years a subject with a major impetus for research. The textured surface is a surface with regulated forms of micro topographies. This micro topographies are creating a film of lubricant when there are not accomplished the conditions for the effect of hydrostatic lift. While the positive implications of the textured surfaces are well known by developing the films thickness for couples with nominal parallel surfaces, associated obviously with the drastic reduction of friction, until now they only aimed seals front, the couple-piston cylinder and axial bearings.

For researches usually there are used two modes of texturing: full texturing and partial texturing. The last one it more effective, concerning the load capacity, in mechanical face seals [2], thrust bearings [3], or thermal engines [4] .The deference is that full texturing is based on the individual dimple effect and partial texturing based on the collective effect of the dimples [5].It is also known that pocket texture performs better than partial texturing for hydrodynamic bearings [1]. This document attempts to establish the effect of pocket texture in the application concerning a hydrodynamic journal bearing. The results should give a clue of what is to expect if we full texture a hydrodynamic journal bearing.

TEHNOLOGIA INOVATIVĂ – Revista „Construcţia de maşini” nr. 3 / 2009

48

2. THEORETICAL MODEL This model is based on the classical Reynolds equation. The Reynolds equation results from the continuity equation for bidirectional flow (1).

0=+z

qx

q zx

δδ

δδ

(1)

Where qx and qz are the unitary flow rate on x and z direction. This results by integrating the speed with the thickness of the lubricant film.

zphwdq

hUxphudq

h

yz

h

yx

δδ

η

δδ

η

⋅⋅

−==

⋅+⋅−==

∫

∫

12

2123

0

0

3

(2)

where, U is the speed, h is the film thickness and η is the dinamique viscosity. By introducing these values for the unitary flows in the continuity equation and considering the flow isothermal we obtain the equation (3) meaning the classical Reynolds equation for laminar, bidirectional flow for an incompressible fluid.

xhU

zph

zxph

x δδη

δδ

δδ

δδ

δδ

⋅⋅⋅=

⋅+

⋅ 633 (3)

For the simplification of the model the following assumption for hydrodynamic lubrication are considered valid [6]:

• The flow of the fluid is considered laminar • The regime of flowing is isothermal • Static load • There are no cavitations effects • The lubricant is a Newtonian liquid

In figure 1 is represented the theoretical model of pocket journal bearing. With pointed line can be observed the pocket geometry on the bearing surface. This geometry is variable, i.e. the tree dimensions of the pocket are modeled in the range of values described in table 3.

Fig. 1. The geometry of the theoretical model

The subject of this research is the geometrical modeling of a pocket journal bearing to get:

• A maximum thickness of lubricant film • A minimal power dissipation

The geometrical modeling is performed by the software Accel, realized by professor Dominique Bonneau, member of LMS Angouleme, France. The program is based on the Reynolds equation. The validity of the Reynolds equation when applied to pocket bearings has been confirmed in [7]. The bearing is subjected to a low load of 3000N and after at a high load of 10000N. The study concerns the influence of the pocket geometry for the two targets in the hydrodynamic lubrication regime. The journal bearing works at a frequency rotation of 4000 rpm and has the following geometrical configuration. Table 1. Geometrical data

Diameter Width Radial clearance

Number of feeds

mm mm mm [0,10]

48 19.37 0.02 1

Table 2. Lubricant characteristics

Viscosity of

lubricant

Lubricant density

Lubricant specific

heat

Lubricant’s proportion

in the mixture

Pa.s Kg/m3 J/Kg/ºC [0-1]

0.01 900 2100 0.5

The three dimensions of the pocket were modeled one by one using the range of values for the dimensions of the pocket presented in table 3.

F

0π 2π

L

b

s

feed

hmin

pocket pocket Sleeve


49

Table 3. The range of values for the dimensions of the pocket

Circumferential length (L) Width (b) Depth (s)

◦ mm µm (0-360) (0-19.37) (3-20)

The performances of theoretical model were compared with those of the classical model of a hydrodynamic journal bearing and due to that comparison we obtained the final results.

3. RESULTS AND DISCUSSIONS

The first step is the pocket width (b) model when the bearing is charged with a minimal load of 3000N. The optimal value obtained for the film thickness is h = 0.006472 mm, so for the pocket with b = 10.34 mm the thickness of the film increases by the reference with 2.24%. We use this value obtained for modeling the second dimension, circumferential length. The optimal value obtained for the film thickness is h = 0.007178 mm, so the circumferential length L = 210 mm increases the film thickness by the reference with 13.39%. By modeling the depth of the pocket we obtained for, s = 20 µm a gain of 37.86% in film thickness. (h = 0.008727 mm).

Fig.2. The variation of film thickness depending

on the width of the pocket By taking the same steps we obtained a decrease of the dissipated power by the reference with 33.67%. (P=14.33W) for the next geometrical configuration: b =16.36; L=210°, s =20 µm.

Fig.3. The power dissipation variation with

the pocket depth

For the maximal load of 10000N we obtain during the same method the further diagrams for film thickness and power dissipation (fig 4, fig 5). The optimal value obtained is h = 0.0035 mm, so for L=210◦; b=10.34 mm; s = 10 m on increase the thickness of the film by the reference with 18.9%.

Fig.4. The variation of film thickness depending on the width of the pocket

Fig.5. The power dissipation variation with the pocket depth

TEHNOLOGIA INOVATIVĂ – Revista „Construcţia de maşini” nr. 3 / 2009

50

The optimal value obtained is P = 18.89 W, so for L=210◦; b=16.36; s = 10µm the power dissipated is reduced by the reference with 33.48%. The differences of the pressure distribution can be well observed at a maximal load of 10000N than at the minimal load of 3000N. Although the maximal pressure is bigger for the classical journal bearing the difference is not significant and due to the fact that the carrying capacity zone knows an important increase for the pocket journal bearing, we can say that this special type of bearing is preferred.

Fig.6. The pressure distribution in a classic

journal bearing

Fig.7. The pressure distribution in a pocket

journal bearing

4. CONCLUSIONS

The optimal pocket dimensions, generated by geometrical modeling with Accel, that allow either the minimization of power lost either the maximization of the minimal film thickness in the bearing, under the two imposed nominal loads are presented in table 4 and table 5.

Table 4. The centralized results of the study for film thickness

F[N]

b[mm]

L[º]

s[µm]

[%] Gain in minimal

film thickness

3000N 10.34 210 20 37.86

10000N 10.34 210 10 18.9

Table 5. The centralized results of the study

for power dissipation

F[N]

b[mm]

L[º]

s[µm]

[%]Drop in

dissipated power

3000N 16.36 210 20 33.67

10000N 16.36 210 10 33.48

Due to this positive results and due to the fact that they can be compared with the results obtained for a textured journal bearing[1] we can say that this research represents the first stage in the study of full texturing surfaces of hydrodynamic journal bearings. We say full texturing because we take into account the presence of a just one pocket on the bearing surface. The only flaws that textured surfaces implicate are for the moment, the manufacturing costs, and the laser technique being the most expensive one but also the most precise.

REFERENCES

[1] Mihai Dobrică, Mircea Pascovici, Michel Fillon and Traian Cicone, Texturing effects in plane-inclined slider bearings,International Joint Tribology Conference, october 2007.

[2] Etsion, I., Laser Surface texturing – Measure to Reduce Friction, 14th Int. Colloquium Tribology, Esslingen, Vol. I (2004), pp. 329-334.

[3] Raghavendra Rao, R., Prasad, K.R. Effects of Velocity-slip and Viscosity Variation on Journal Bearings, ANZIAM Journal, 46 (2004), pp. 143-155

[4] Klingerman, Y., Shinkarenko, A.,Etsion, I. Improving Tribological Performance of Piston Rings by Partial Surface Texturing, 2004 AIMETA Conf., Rome, 2004, pp. 607-614

[5] Feldman, Y, Klingerman, Y., Etsion, I. Stiffness and Efficiency Optimization of a Hydrostatic Laser Surface Textured Gas Seal, Journal of Tribology, 129 (2007), pp. 407-410

[6] Pinkus, O., Sternlicht, B. Theory of Hydrodynamic Lubrication, McGraw-Hill, New York, 1961

[7] Dobrica, M.B., Fillon, M., 2005, Thermohydrodynamic behavior of a Slider Pocket bearing, ASME J. of Trib., 128, pp.312-318.

F=10000N

pmax =0.4520*1.E+02MPa

b=7.32 mm

L=210º

S=10µm

pmax=0.3561*1.E+02MPa


51

SLIP/NO-SLIP INFLUENCE ON THE BEHAVIOR OF A RADIAL BEARING WITH A STATIC LOAD. HD ANALYZES

Daniela Coblaş *, Aurelian Fătu**, Alexandru Rădulescu***

* University of Polytechnics, Bucharest, ROMANIA, e-mail: [email protected]

** University of Poitiers, FRANCE, e-mail: [email protected] *** University of Polytechnics, Bucharest, ROMANIA, e-mail: [email protected]

ABSTRACT This paper aims to examine the influence of wall slip on HD lubrication performance of a journal bearing. The study follows two main directions: first to increase fluid film thickness to obtain a greater load capacity and second to reduce power loss. By numerical modelling, we had modified the geometric parameters of a slip surface placed on the sleeve bearing. Results show that for a well chosen surface geometry it is possible to improve the bearing performances.

. KEYWORDS: Wall slip, Journal bearings, Lubrication, Numerical modelling.

1. INTRODUCTION Lubrication is considered one of the most

important factors for the tribologycal research field and involves the study of all phenomena associated with the operation of friction couples.

The importance of studying this phenomenon and the lubrication regime is reflected in the technological area by several directions: the consumption of energy, materials and lubricants, the increase of load capacity, life length and reliability of service for all the mechanical components, [1], [2].

The objective of this paper is the optimization of operating parameters for a radial bearing, part of an internal combustion engine (ICE), which has a slip/no-slip surface defined on the surface of the pad. The computation was possible only by using a modelling program, to change the geometric parameters of the slip zone and see the variation for the bearing parameters for each case.

The analysis followed two main directions: increasing fluid film thickness which leads at a greater load capacity and reducing the loss of power by friction phenomenon.

2. THE PHENOMENON SLIP/ NO-SLIP

To describe the flow of a fluid in a given

situation it is necessary to specify the boundary conditions of flow. When the region occupied by the fluid is bounded by a solid surface, the fluid cannot cross. His speed is necessarily zero in the normal

direction at surface. However, it is not necessarily zero in the tangential directions.

In fluid mechanics, it is traditional to consider that the tangential velocity at a solid surface is zero, and the fluid does not slip on it. This assumption is the condition of “no slip”. But previous studies have shown that the slip phenomenon sometimes appears at the fluid –solid contact at microscopic level and involves the study at molecular scale, [3], [4].

The most commune case of slip is found in nature known as the “Lotus Effect” and it imply the superhydrophobicity of leaf surface that makes the water drops slide and roll on the surface. Water molecules located in the contact zone are not adhering at the solid ones but they partially slide on them. The result is the advance of the water drop on the leaf surface, [5].

Figure 1. Fluid-solid contact area

on the leaf surface.


52

The slip/no-slip phenomenon it is also favoured by the presence of a non-wetting surface, low pressures and low roughness.

When making the transition to a tribologycal model (fig.2), we place the slip surface on the sleeve bearing and the result is a modified velocity profile.

Figure 2. Velocity distribution for Couette flow, fluid film between two surfaces,

case with (optimized bearing) and without slippage at the surface (classical bearing).

For the classical case, at the contact with the

sleeve bearing surface, fluid velocity is equal to zero. For the optimized case, this velocity is no longer naught, but equal to the slip velocity of the fluid in that area. It can be observed also that fluid velocity at the contact with the bearing axle (mobile surface) has the same value for both cases.

Slip phenomenon is influenced by many factors like: strength of liquid-solid interaction, roughness of the surfaces, nature of the interface, operating conditions (the influence of the friction phenomenon, the film pressure, the dispersion of gas), the electrical properties of liquid (dipole moment, salinity).

Previous studies show that the slip/no-slip surface must be defined on the fixed bearing surface, the sleeve surface. If the slip/no-slip surface is defined on the mobile surface then the increase of the load capacity is not possible. It has also been shown that using a sliding surface with a complex geometry can lead to a significant increase of load capacity and the reduction of power loss.

Another important aspect is the shear stress influence. It was observed that the increasing tension over a critical value leads at the appearance of partial slip of the fluid molecules. The conclusion is to impose an initial limiting for this parameter, a limit that must be exceeded to obtain the slip mode.

Surface roughness is one of the other important parameters, and it must be as low as possible to ensure the apparition of the slip phenomenon.

The bearing eccentricity has also a very important role. Even if the slip surface is well-defined, the performance level may be damaged if this ratio increases sharply.

Another important parameter is the fluid film thickness. This parameter has a direct influence on the load capacity. The value of this parameter also influences the lubrication regime of the bearing. It should not fall below 3 µm for the hydrodynamic regime (HD), and 1 µm for the elasto-hydrodynamic regime (EHD). For sparingly values of this parameter the lubrication regime sometimes crosses from fluid to mixed, implicating the contact between surfaces micro-roughness and the load capacity is affected. It has also been proven by other studies that the phenomenon of slip begins in the area with the smallest value of thickness is moving towards areas with larger thickness.

Generally the lubricants used must have a low viscosity to reduce the friction at fluid contact with solid surfaces.

3. THE STUDIED MODEL,

JOURNAL BEARING

The model analyzed is the first level of the crankshaft of a diesel engine with a capacity of 1500 cc. It is a radial bearing, which can operate in various lubrication regimes (dry, mixed, fluid).

The fluid friction regime presumes the existence of a continuous fluid film between the bearings walls, with a minimum thickness of 2-3 µm to prevent contact between surfaces micro-roughness. For this case, film thickness will be maintained at a value above 3 µm, to avoid the transition between the fluid and mixed lubrication.

The slip/no-slip surface is defined on the sleeve bearing surface, as highlighted in Figure 3.

Figure 3. Definition of the slip/no-slip zone

on the sleeve bearing.

Sleeve Bearing

Clasic Profile Modified Velocity Profile

Axle

Slip surface

Axle Velocity

Housing surface

Axle

Feeding groove

Fluid film

Slip zonex

z

F (load)

Slip zone

Housing surface

Feeding groove

x

y ls

Ls


53

Table 1. Model parameters. Parameters Measure Unit Value

Bearing diameter mm 48.00 Width of pad mm 19.37

Radial Bearing mm 0.20 Speed shaft Rpm 4000

Type of fluid - Newtonian

To study the influence of each parameter value was varied and the values for the other two parameters were kept constant. In the process of surface modelling the parameters were modified in this order: width (ls), length (Ls), and slip coefficient (C), with a range of values indicated bellow.

Table 2. Slip surface geometry.

Slip surface parameters Measure Unit Range

Width [mm] [0-19.37]Length [deg] [0-360]

Slip coefficient - [0-100]

4. RESULTS AND DISCUSS

For the hydrodynamic case the optimization of the sliding surface led to important results for small loads, as it can be seen in the result tables. All the values obtained were compared with a reference case, the classical bearing case, without slip surface. Table 3. Results obtained when increasing minimum

film thickness.

Load Geometric parameters

Variation of performance parameters

h [%] + 0.18 10.000 N

ls = 1.08 mm, Ls = 90 deg , C = 20-40 Pf [%] - 0.7

h [%] + 8.13 1500 N ls = 8.08 mm, Ls = 180 deg , C = 20 Pf [%] -17.9

h [%] + 19.91 750 N ls = 10.59 mm, Ls =

180 deg , C = 100 Pf [%] -25.8

a)

b)

c)

Figure 4. Minimum film thickness variation with the surface width (a), surface length (b)

and the slip coefficient(c), for static loads of 750, 1500 and 10.000 N.

Table 4. Results obtained for power loss reduction.



h [%] -28.50 10.000 N

ls = 16.86 mm, Ls = 180 deg , C =

10 Pf [%] -35.30

h [%] -38.40 1500 N

ls = 18.12 mm, Ls = 180 deg , C =

10 Pf [%] -20.74

h [%] - 40.10 750 N ls = 18.12mm, Ls =

180 deg , C = 10 Pf [%] - 8.70

a)


54

b)

c)

Figure 5. Power loss variation with the surface width (a), surface length (b) and the slip coefficient(c),

for static loads of 750, 1500 and 10.000 N.

Comparison with the Classical Case

Figure 6. Pressure distribution at the sleeve surface level for the classical bearing (a)

and the optimized bearing, increasing the minimum film thickness (b) and power loss reduction (c).

As seen in the pictures above for the optimized bearing the pressure distribution is modified, generating performance improvement.

5. CONCLUSION

The main conclusion of the present study is

that for an optimal geometry of the slip/no-slip surface, defined on the housing surface (the sleeve bearing surface), we can obtain a performance improvement for the steady state bearing.

The improvement is materialized in an increase of minimum fluid film thickness (with 19.91 %) and a reduction of power loss (with 40.1 %) that imply many economical aspects: material and lubricant economy (a smaller optimized bearing can support the same load as a classical bearing with greater dimensions), energetic improvement (reducing the energy needed to assure the movement of the mobile surface), the possibility of increasing the load (for the same dimensions but with optimized surface).

However, for this model, operating in HD regime, an improvement is possible only for small load values.

We also find that some inappropriate geometry can lead to a decrease of bearing performances, by reducing fluid film pressure and loosing bearing load capacity.

The positive results obtained point for future analyses of the same model and operating conditions closer to actual operating mode, involving surface deformation, temperature influence and dynamical loads.

BIBLIOGRAPHY

1. Frene, J., Nicolas, D., 2001, “Lubrification Hydrodynamique, Paliers et butées ”, 1990, Editions Eyrolles, Paris, France.

2. Spikes, H., 2001, “Tribology in the twenty-first century”, Tribology Section, Imperial College, Mechanical Engineering Department, London, pp 789-799.

3. Fătu, A., Hajjam, M., Bonneau, D., 20-22/10/2008, “Wall Slip in EDH Journal Bearings”, International Joint Tribology Conference, Miami, Florida.

4. Ma, G.J., Wu, C.W., 11/10/2005, “ Squeeze fluid film of spherical hydrophobic surfaces with wall slip”, Laboratory of Structural Analysis for Industrial Equipment, Department for Engineering Mechanics, Dalian University of Technology, Dalian 116024, China, pp 863-872.

5. *** www.wikipedia.com


55

SLIP/NO-SLIP INFLUENCE ON THE BEHAVIOR OF A RADIAL BEARING WITH A STATIC LOAD. EHD

ANALYZES

Daniela Coblaş *, Mohamed Hajjam**, Alexandru Rădulescu***

* University of Polytechnics, Bucharest, ROMANIA, e-mail: [email protected]

** University of Poitiers, FRANCE, e-mail: [email protected]*** University of Polytechnics, Bucharest, ROMANIA, e-mail: [email protected]

ABSTRACT In this paper we present a study on the behavior of a steady-state radial bearing assuming the existence of slip phenomenon at the fluid-solid interface with the sleeve bearing wall. The bearing operates in elasto-hydordynamic lubrication regime, disconsidering thermal influence, and taking into account the general assumptions considered for determining Navier-Stokes equation for the general hydrodynamic lubrication case. Like presented in the previous article, the computation was possible by using numerical modeling software Accel, available thanks to LMS Laboratory, belonging to Poitiers University. Only by using this software, the available time we had was sufficient to perform this study. .

KEYWORDS: Wall slip, Journal bearings, Lubrication, Numerical modelling.

1. INTRODUCTION

The present paper comes as a continuation of the previous article, which presents the analysis of a steady-state radial bearing, with hydrodynamic (HD) lubrication, ignoring elastic deformation of the surfaces that defines the gap. In this case, the elasticity is taken into account, and the bearing is considered operating in EHD regime, [1], [2].

It is known that EHD lubrication involves the elastic deformations of surfaces, for some component parts of the assembly, even if those are completely separated by a lubricant film, [3], [4], [5].

Figure 1. Pad deformation in operating mode.

Because of high local pressure surfaces are

subjected to deformations during the operating time,

(figure 1), which exerts an influence over film thickness and pressure distribution, like shown in figure 2.

Figure 2. Surface deformation and Pressure distribution for HD (a) and EHD case (b).

Given the characteristics of EHD regime, the

model was subjected to higher loading forces than the previous case, 10000 and 15000 N.


56

2. METHODOLOGY The analysis is made for the same model,

with same dimensions and characteristics (). A Newtonian lubricant is used, and we make the same assumption, that slip occurs along the sleeve bearing wall. Using the same calculation methodology, the modeling software Accel, we modified the values of the slip surface geometric parameters.

Table 1. Model parameters. Parameters Measure Unit Value

Bearing diameter mm 48.00 Width of pad mm 19.37

Radial Bearing mm 0.20 Speed shaft Rpm 4000

Type of fluid - Newtonian

In the process of surface modeling the parameters were modified in this order: width (ls, between 0 and 19.37 mm), length (Ls, between 0 and 360 deg), and slip coefficient (C, between 0 and 100).

C, the slip coefficient is a non-dimensional parameter defining the intensity with which slip occurs, its value maybe greater than 100 but we find out that after a certain value, mostly the optimum value considered, it doesn’t exert any other influence on the operating behavior.

The mathematic equation used for this study is a modified Reynolds equation, which has new terms due to slip assumption, and it can be seen in ref. 3.

The results obtained are satisfactory, we achieved to find an improvement of bearing performances for this case too.

3. RESULTS AND DISCUSS For EHD case, by modeling the geometry of

slip zone we have obtained better results for the smaller load (equal to 10.000 N) then for a greater one (15.000 N). Film thickness was increased with 31. 32% and power loss was reduced with 48.90 %.

Table 2. Results obtained when increasing

minimum film thickness.



h [%] 31.32 10.000 N

ls = 14.35 mm, Ls = 180 deg , C = 80 Pf [%] -34.5

h [%] + 29.07 15.000 N

ls = 15. 61mm, Ls = 170 deg , C = 70 Pf [%] -34.5

a)

b)

c)

Figure 3. Minimum film thickness variation with the surface width (a), surface length (b) and the slip coefficient(c), for static loads

of 10.000 and 15.000 N.

Table 3. Results obtained for power loss reduction.



h [%] - 48.9 10.000 N

ls = 16.86 mm, Ls = 180 deg , C = 10 Pf [%] - 1.5

h [%] - 41.5 15.000 N

ls = 18.12 mm, Ls = 170 deg , C = 70 Pf [%] - 12.1


57

a)

b)

c)

Figure 4. Power loss variation with the surface width (a), surface length (b) and the slip coefficient(c),

for static loads of 10.000 and 15.000 N.

4. THE LOSS OF LIFT BEARING During the computation time, we met

situations where the surface geometric parameters were limited to certain values, due to the appearance of fluid film ripping and transition between fluid and mixed service character.

When length (Ls) exceeds a certain value (180 deg or 240 deg in some cases) fluid velocity (expressing its passing thru the gap) grows rapidly and leads to a sharp increase of pressure in the swell zone (when passing from slip zone to the unmodified surface). The result changed distribution of pressure with a large range of small values. This leads to the loss of lift bearing capacity and charging impossibility.

The explanation is that there are insufficient resisting forces to cancel the effect of load forces.

The minimum pressure values, almost naught at some points, lead to the apparition of contact between solid surfaces, and it means that in these areas the presence of lubricant may be inexistent.

Figure 6. Lifting capacity loss, for an excessive

length of the sliding surface.

Pressure abnormal distribution may be also correlated with the eccentricity ratio which has a different variation depending on load forces, influencing film thickness.

Comparison with the Classical Case Figure 5 shows the modified pressure

distribution for the optimized bearing, comparing it with the classic bearing, and reveling the mathematical meaning in this optimization.

Lift Capacity Loss

Slip

Slip

No- Slip

Sleeve Surface

Slip Zone

Slip Zone

Slip Zone

Axel SurfaceAxel Velocity

Slip Velocity

h

Sleeve Surface

Sleeve Surface


58

It is easy to see the difference between the two surface integrals, and one can imagine the different resulting values giving the actual improvement.

Figure 5. Pressure distribution at the sleeve surface level for the classical bearing (a) and the optimized

bearing, power loss reduction (b) for a load of 15.000 N.

5. CONCLUSION

As we conclude in the previous article to, by considering the appearance of the slip phenomenon and by modeling the slip surface geometry, we achieved to improve bearing behavior for the steady state EHD operating mode.

Minimum film thickness was increased with a 32.31 % and power loss was reduced with 48.01%, for a load of 10.000 N.

We showed how an inappropriate geometry of slip zone can lead to the loss of the bearing lifting capacity.

As concluded in ref. 3, one of the issues raised by construction of this type of bearing is the life length of modified surfaces, issue that will find its question along the development of manufacturing technologies for this type of surfaces, which at this time imply high costs.

Computer assisted simulation has proved its usefulness and also the necessity of this type of solutions and their development, in order to have the possibility to adjust each one for different research themes.

BIBLIOGRAPHY

1. Cottin-Bizonne, C., 2002, “Hydrodynamique a l’interface

solide-liquide: etude par medures de forces de surfaces et simulation de dynamique moléculaire”, Lab. Physique de la Matière Condensée et Nanostructures, Université Claude Bernard Lyon I, France.

2. Bayada, G., Benhaboucha, N., Chambat, M., 11/09/2007, “Wall slip induced by a micro polar fluid”, INSA-Lyon, CNRS UMR 5208-5259, Villeurbanne, France, pp 89-100.

3. Yingxi, Z., Granick, S., 10/08/2001, “Rate-dependent slip of Newtonian liquid qt smooth surfaces”, Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801, pp 0961051–0961054.

4. Yingxi, Z., Granick, S., 27/10/2002, “No-slip boundary condition switches to partial slip when fluids contains surfactant”, Department of Materials Science and

Engineering, University of Illinois, Urbana, Illinois 61801, pp 10058-10063.

5. Ma, G.J., Wu, C.W., 10/12/2004, “ Abnormal behaviour of a hydrodynamic lubrication journal bearing caused by wall slip”, Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Dalian University of Technology, Dalian 116024, China, pp 492-499.

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European brokerage event on urban mobility Event Type: Brokerage Events Start Date: 17-Nov-2009 End Date: 18-Nov-2009 City: Montbéliard Country: France

Description: Enterprise Europe Network Grand Est in France is organising a brokerage event during the International Conference MOBILIS that will take place in Montbéliard(Franche-Comté - East of France) from 17th to 18th of November 2009. The conference is organised by the Vehicle of The Future, a National competitiveness cluster. The conference is dedicated to urban mobility. The last edition of the conference that took place in november 2008 is online : www.mobilisconference.com The topics of the brokerage event are the following : URBAN CLEAN VEHICLES Type of vehicles - Vehicles for persons or goods transportation, for services - urban or peri-urban environment - individual or collective use… Engines, motors - electric, - gas - hybrid - thermal, … Energy storage Batteries, Hydrogen Fuel cells… DRIVING SMART SYSTEMS - to facilitate navigation (geopositioning, embedded systems, data exchanges,…) - to help driving (driver assistance) - for maintenance, fleet management - for booking or payment… MOBILITY MANAGEMENT - Simulation or traffic optimization - Modal transfer or intermodality - Parking systems… INNOVATIVE MATERIALS, PROCESSES AND SYSTEMS TO IMPROVE SUSTAINABILITY, ERGONOMICS, COMFORT, SECURITY. smart sensors, signal treatment, engine parts, integration…


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THEORETICAL RESEARCHES REGARDING THE STATIC BEHAVIOUR OF A TRANSVERSAL SLIDE

FOR MULTIFUNCTIONAL MACHINE TOOLS

Raluca Magdalena Nita, Loredana Paun, Roxana Grejdanescu

SC ICTCM SA, Bucharest, ROMANIA, e-mail [email protected]

REZUMAT Lucrarea isi propune studiul prin metoda elemetelui finit a comportatii statice a unui ansamblu sanie transversala, componenta aunei masini unelte multifunctionale, sub actiunea fortele in timpul functionarii, in situatia in care sania este facuta din material clasic (otel sau fonta) cat si din material compozit pultruzionat. Prezinta importanta determinarea performantei, fiabilitatii, rezistentei si sigurantei in functionare deoarece acestea reprezita caracteristici fundamentale ce au o influenta deosebita asupra rezultatelor finale ale procesului de prelucrare. ABSTRACT The paper aims to study with the finite elements method the static behavior of transversal slide, component of a multifunctional machine tool, under the function during processing, in the conditions of steel and a composite slide. It’s very important to determine the performance, resistance and security in functioning because this represent fundamental characteristics on the final results of the processing process. KEYWORDS: machine structure, composite, finite element analisys, static comportament CUVINTE CHEIE: structura masina, compozit, analiza cu element finit, comportare statica

1. ASPECTS OF THE FINITE ELEMENT ANALISYS The finite element method is an approximate numerical method for calculation, which can be used where is necessary for calculating the specific strains, the displacements and tensions, if a well definite dimensional geometry, for a loading, for well-defined boundary conditions and for material with known characteristics.[7] In case of an analysis of a complex system, such as in a cross sled of a multifunctional machine tools, is an important step of the analysis with the finite element method and is the specification of the characteristics of contact, which depends on the elastic properties of bodies that come in contact, the their geometry, but also how they are applied the loads acting on the system analyzed, because during their application size and shape of surfaces in contact may change. You can also change the distribution of tensions in these areas [1], [6].

For o more exact simulation of the problems that appears at the body contact, the contact technology it is rigorous implemented in the interfaces that help the user in them simulation, in order the obtained results to be as precise as possible even in the complex system cases. In the desing stage are used CAD programms (Computer Aided Design) of them data files represented the design product [5] Those files proper for the CAD program that you use, presents through others (materials, deviations, etc.) spatial geometry (3D), complete or partial, of the structures, pieces which are designed [5]. The CAD file is assumed in the proccesors of the MEF programs, even if the calculation model with MEF it doesn’t always correspond with the real geometry of the calculation structure, much more, this transfer could not be complete, because of some incompatibilities between the way of stockage and interpretation of the data in the two programs (files known by the program) [5].


60

For these reasons, after the data bases transefer in the MEF program, the calculation model geometry must be corrected or adapted to the program. Data bases created in CAD programs are in general proper for every program and sometimes can be converted in standardized forms. One of the most used type of files for the datebase transfer between the programs is the IGES file (Initial Graphics Exchange Specification), which has the extension igs [5]. 2. SPECIFIC SOLICITATIONS SPECIFIC FOR THE NEW INTEGRATED MATERIALS The multifunctional machines tools should also ensure that high speed processing, in high reliability conditions, requiring high precision, reliability and durability in operation increased. [8] For processing with high speed for operation of the high precision conditions, is necessary to use materials with low specific weight. The pultrusionated composite materials are heterogeneous and anisotropic materials so that their mechanics is more complex than that of conventional materials [8]. The basic element of a laminated composite structures is the individual layer (laminate) reinforced unidirectional fiber inserted into a resin (matrix).[9] As shown in figure 1, in the general case, request a lamine plan consists of three components were reported in the main directions in the material: Longitudinal application - the normal stress σ║ direction is parallel fibers [9]; Transversal application - the normal tension σ┴ acts perpendicular to the direction of fibers; Request tangential - caused by tangential stresses τ # acting parallel and perpendicular to the direction of fibers. Defining the three requests are made on a representative volume element of the laminate. On the macroscopic laminate can be imagined as a "Anisotropic homogeneous continuous element” [9], in which the fibers of infinite length are inserted into the matrix. The transversal section of laminate is not homogeneous so that the calculation is made with medium tension. These composites materials are pultrusionat profiles formed by rovings of glass by spun glass embedded in a resin thermal mass[2]. For the purpose that the pultruzionate profiles were designed, they are built by dragging the rovings of spun glass after the fibers were molten by resin, through a special molds where is determinate the designed profile and, after heating with melting fibers through resin, stabilization occurs with cooling profile shape, sizing and cutting it to length, which gives them the end of manufacture very high stiffness elements.

The characteristi properties of the composites material from witch are made the slides are presented in table 1 and the values for the characteristic rigidities in table 2. All this values are valable for temperatures between -200C and 600 C. [9]

Figure 1. Stratified composites and the solicitations

for an element volum of the lamina [9]

Table 1. Characteristic stress [9] Specific loodings MPa Bending force on logitudinal direction

fb,0° 240

Bending force on transversal direction

fb,90° 100

Traction force on logitudinal direction

ft,0° 240

Traction force on transversal direction

ft,90° 50

Compresion force on logitudinal direction

fc,0° 240

Compresion force on transversal direction

fc,90° 70

Shearing force fτ 25

Table 2. Values for the characteristic rigidity [9] Material characteristics

[MPa] [--]

Elascity module on longitudinal direction

E0° 23 000 / 28 000

Elascity module on transversal direction

E90° 8 500

Tangential elascity module

G 3 000

Poisson coeficinet

v0°,90° 0.23

Poisson coeficinet

v90°,0° 0.09


61

3. GENERATING THE FINITE ELEMENT MODEL. The fist step in finite element method analisys it is the model elaboaration and in special structure meshing, in another words passing from the phisical material from which the structure is being executed, to the conventional model- dicreet, for which will be done the finite element analisys. (FEA).[6] Very important problems that are taken into consideration when it is done the meshing are the nodes number: maximum and minimum; elements type; number of elements: maximum and minumun elements; maximum and minimum dimensions of the elements, imposed by the structures details and the calculation aim. Meshing process si a very complex one and has as scope optaining of an approach as better as possible of the real structure, from geometrical point of view, of the way of forces application of the forces, of the gidities, of the masses [5],[6]. Through this the study of the infinite points of the continuous given structure it is approximated through the study of the finite number of points – bends – of the meshing array of the discrete model [5]. The discreet mesh approximate, from mechanical and geometrical point of view the real structure. Meshing should be realized through an as uniform as possible array from lines and/or surfaces for model elaboration, processing and result interpretation to be as simple. The model was meshed with 10952 elementes and 22455 nodes as in fig. 2. The static analyses of the transversal slide behaviuor assumes the determination of the static deformations of the structure under the distribuite pressure action under the conditions of using different tipes of materials as composite and steel [8]. Distribuite pressere it is applied on the superior face of the transversal slide as in fig. 3.

Figure 2. Meshing array

Figure 3. Solicitation of the transversal slide

Distribuite pressure value is 0.21 MPa, and is progressively applied in time of o second as in fig. 4. 4. RESULTS OF THE STATIC BEHAVOIUR OF A STEEL TRANSVERSAL SLIDE After the simulation program development the post processing represents the phase of effectively examining of the results, in tabular of in graphic form. The graphic representation of the results it is easier for interpretation and more facile for the user. It were taken into consideration for comparison the total deformation, the total deformation along x axis, equivalent elastic strain and maximum principal elastic strain.

Figure 4. Distribuite pressure

Figure 5. Total deformation

Figure 6. Maximum deformation on X direction


62

Figure 7. Equivalent elastic strain

After the simulation were obtained the folowing results: total deformation it is aproximatevely 0.39 mm (fig. 5), the maximum deformation on X direction 0.016 mm (fig. 6), equivalent elastic strain 0.005 mm (fig. 7), maximum principal elastic strain 0.0005 mm (fig. 8). 5. RESULTS OF THE STATIC BEHAVIOUR OF A COMPOSITE TRANSVERSAL SLIDE The results of the static behaviour of a composite transversal slide are presented in figure 8 …12.

Figure 8. Maximum principal elastic strain

Figure 9. Total deformation

Figure 10. Maximum deformation on X direction

Figure 11. Equivalent elastic strain

Figure 12. Maximum principal elastic strain

After the simulation were obtained the folowing results: total deformation it is aproximatevely 3.4163 mm (fig. 9), the maximum deformation on X direction 0.14 mm (fig. 10), equivalent elastic strain 0.00495 mm (fig. 11), maximum principal elastic strain 0.00508 mm (fig. 12).


63

CONCLUSIONS Finite elements method is a numerical method to analyze problems related to mechanical deformable structures through which were calculated specific strains, displacements and stress. In this case was used fot the determination of the static behaviour, from specific deformations and displacements of the transversal slide of a multifunctional machine tool, under the condition of executing the slide from composite and steel. After results post processing were effectively examined the simulations results was determined that under the condition of bending the same distribuite presseure at the composite slide are recorded deformations 10 times bigger as at the steel slide.

REFERENCES [1] Mihailidis A, Pupaza C., Nerantzus I, Karaoglnidis G.,

Modeling and simulation of o spherical bearing mount, Annals of DAAAM for 2008 & Procidings of the 19th Internationl DAAM Symposium, ISSN 1726-9679 ISBN 978-3-901 509-68-1.

[2] Suh, J.D., Lee, D.G, Composite Machine Tool Structure for high Speed Milling Machines, Annals of DAAAM for 2008 & Procidings of the 19th Internationl DAAM Symposium, ISSN 1726-9679 ISBN 978-3-901 509-68-1.

[3]. Bathe, K.J (1990) Finite Elementen Methoden, Springer Verlag, ISBN 0-387-15602-X, Berlin.

[5] Ghionea Ionut, Considerations about the methodology and rezults for the finite elemenent analysis of a mechanical assembly, Proceedings of the 16th Intenational Conference on Manufacturing Systems- ICMaS, ISSN 1842-3183.

[6] Sorohan, S, Constantinescu, I, Practica modelarii si analizei cu elemente finite, Bucuresti, 2003.

[7] Zienkievicz, O, The finite element method, Heinemann, 2000, ISBN 0 7506 5049 4.

[8] Schmitz, t. L. And Donalson, r. R., 2000, Predicting High Speed Machining Dynamics by Substructure Analysis, Annals of CIRP, 49/1:303-308.

[9] Fiberline composites, www.fiberline.com, Accesed on 2009-02-20.

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Process Engineer - Instrumentation

Top five dominate process level measurement device supplies The market for level measurement devices remains robust as manufacturers continue to launch new instruments and drive new projects forwards. Sean Ottewell reports

A new market study by VDC Research on the global process level measurement market finds that the top five suppliers of process level measurement devices world-wide are: Endress+Hauser, Emerson Process Management, VEGA Grieshaber, Yokogawa Electric Company, and Siemens Milltronics Process Instruments.

Emerson Process Management and Siemens lead the way in shipments of the two largest product categories - hydrostatic devices and sonic/ultrasonic devices.

"While these five suppliers of process level measurement devices have the lion's share of the market, it is critical to remember that this market is highly fragmented, with dozens of other segment leaders operating

in very specific technical or installation environment niches," indicated Chris Rezendez, Executive Vice President of VDC Research Group.

The study, which forecasts the market through 2013 also found that: the global market for process level measurement sensors is expected to decline by nearly 15 per cent in 2009 but will begin to grow in late 2010 or the first half of 2011; increased efficiency demands and regulatory compliance drivers are the top factors driving long term growth; the greatest gains in shares are seen in Foundation Fieldbus as the standard is becoming more widely accepted; emerging wireless standards are expected to make inroads into the global market over the forecast period; and worldwide, the verticals exhibiting the strongest now- and near-term performance are chemical/specialty chemical markets, petrochem and pharmaceutical.


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Emerson Process Management has demonstrated its ongoing commitment to level measurement with the new Rosemount 5300 guided wave radar (GWR) level transmitters for SIL2 safety instrumented systems. Following successful third-party evaluation, the 5300 series now comes with the required failure modes, effects and diagnostic analysis (FMEDA) report. As a result, says Emerson, companies in the oil and gas production, refining, petrochemical, chemical and power industries can benefit from the superior performance of GWR technology while ensuring compliance with associated IEC industry standards.

The 5300 Series was evaluated, as per hardware assessment IEC 61508, by global organisation Exida. The resulting FMEDA report, with safe failure fraction (SFF) over 90 per cent, shows SIL2 suitability. As per IEC 61508 and IEC 61511 the documentation provides safety instrumentation engineers with the required failure data and with proof test recommendations. With a five-year-plus proof test interval, the proof test can be co-ordinated with plant turnaround, minimising process interruption and reducing risk to personnel.

The Rosemount 5300 series is a two-wire GWR for challenging level and interface measurements on liquids, slurries and solids. It leverages the company's 30 years of radar expertise and is designed to improve plant profitability through superior reliability, state-of-the-art safety features, effortless handling and unlimited connectivity.

It has an enhanced capability to handle disturbing factors, longer measuring range, and lower dielectrics, even with a single probe. The robust design prevents leakage and performs reliably, especially under extreme process conditions.

Heavy-duty probes are available to meet the extreme temperatures and pressure challenges with multiple layer of protection and advanced echo logics for reliable overfill detection.

he 5300 series' two-wire technology enables fast and inexpensive installation. With user-friendly graphical interfaces and wizards, measure-and-learn functionality, suggestions for application-specific configuration and PlantWeb digital architecture functionality, the transmitter integrates easily into new or existing control systems. This, in addition to maintenance-free operation and advanced diagnostics, results in a quicker return on investment with overall improved uptime and enhanced safety.

VEGA Grieshaber continues its efforts in the same market with an order encompassing the complete level, switching and pressure instrumentation for Germany's largest paper mill. Production start-up in the new paper mill is planned for March 2010.

The order includes, among other things, VEGABAR pressure transmitters with ceramic CERTEC measuring cell, various types of VEGAPULS radar sensors as well as VEGACAP and VEGASWING level switches. The instruments will be used in all areas of the new plant - from stock preparation to paper machine.

The new paper machine has a working breadth of 10.1 m and an operating speed of 1900 metres/minute. Every year, 650000 tons of test liner and corrugated medium are to be produced from 100 per cent recycled fibres in weights from 70-130 g/m2.

In another new move, BASF and VEGA Grieshaber have extended the existing framework contract. The contract covers the worldwide delivery of level and switching instrumentation from VEGA for the manufacturing locations of the BASF Group. According to VEGA, this contract underscores and deepens the trust as well as the successful cooperation between the two companies.

(source http://www.engineerlive.com/Process-Engineer/Instrumentation/Top_five_dominate_process_level_measurement_device_supplies/22149/?dm_i=381,2F9S,76KG1,7NPH,1)


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RECHERCHES EXPERIMENTALES SUR LE COMPORTEMENT THERMIQUE DES LUBRIFIANTS USES

Alexandru V. Rădulescu1, Irina Rădulescu2

1 Université POLITEHNICA de Bucarest, Bucarest, ROUMANIE, e-mail : [email protected] 2 S.C. I.C.T.C.M. S.A. Institut de Recherches Technologiques pour la Construction des Machines, Bucarest,

Roumanie, e-mail : [email protected]

RESUMÉ Cet article propose d'étudier le comportement thermique des lubrifiants frais et usés, en tenant compte de la variation de la viscosité par rapport à la température. Le modèle rhéologique proposé pour les lubrifiants frais et usés est le modèle de Newton, pour lequel les tensions tangentielles dans le fluide sont proportionelles avec les gradients de vitesses. Les informations concernant la viscosité des lubrifiants peuvent être considérées comme une « fenêtre » pour analyser les autres propriétés des fluides. La viscosité est toujour plus facile à mesurer que beaucoup d’autres propriétés des lubrifiants, en constituant un outil très important pour la caractérisation des fluides. ABSTRACT This article proposes to study the thermal behavior of fresh and used lubricants, taking account to the variation of viscosity versus temperature. The proposed rheological model for fresh and used lubricants is the Newton model, where the shearing stresses in the fluid are proportional to the velocity gradient. Information on the viscosity of lubricants can be regarded as a "window" to analyze other fluids properties. The viscosity is always easier to measure than many other properties of lubricants, providing a very important tool for the fluids characterization. MOTS CLEF: comportement thermique, lubrifiants frais et usés, viscosité, temperature KEYWORDS: thermal behavior, fresh and used lubricants, viscosity, temperature

1. INTRODUCTION

D’une manière générale, tous les mécanismes

lubrifiés, à la condition que le graissage ne se fasse à fond perdu, sont susceptibles d’être surveillés dans leur fonctionnement par analyse de leur lubrifiant en service. Les résultats permettent de déceler des anomalies caractéristiques telles que, [6] : la contamination par des particules internes à

l’équipement; l’évolution par comparaison des résultats

obtenus entre chaque analyse; le type d’usure; la pollution par des agents extérieurs entraînant

une détérioration du lubrifiant et/ou une usure par abrasion. Concernant le choix de la méthode de

surveillance du degré d’usure des lubrifiants, on peut mentionner les analyses physico-chimiques évaluant la qualité lubrifiante de l’huile, la détermination de la teneur en produits d’usure,

l’examen microscopique et le comptage de particules en suspension dans l‘huile.

L’interprétation de certains résultats de mesure est souvent délicate notamment parce que l’évolution, jugée anormale, d’un élément de l’analyse peut avoir plusieurs causes. Grâce à une meilleure connaissance des phénomènes d’usure et de dégradation des matériaux ainsi qu’au développement de nouvelles technologies assistées par l’informatique, la maintenance conditionnelle par l’analyse des huiles représent un outil de progrès pour les responsables de maintenance, [1, 2].

Du point de vue de l’instrumentation associée qui permet d’analyser l’échantillon prélevé, il faut remarquer le viscosimètre, l’Aquatest, la chromatographie en phase gazeuse, la méthode Karl Fisher, la mesure du point éclair en vase clos, l’analyseur photométrique de la tache, le spectromètre à absorption infrarouge ou d’émission à torche à plasma, le magnétiseur de particules, le compteur de particules etc.


66

Plusieurs modes opératoire peuvent être appliqués à un même échantillon, d'une part pour analyser différents paramètres caractéristiques de l'huile, d'autre part pour établir un diagnostic objectif de plusieurs techniques concordant sur la même analyse. Aussi, cette sélection dépend de la requête émise par le service qui fait appel à l'analyse des huiles (politique de maintenance liée à l'équipement concerné).

Parmi cettes méthodes utilisées pour analyser le degré d’usure du lubrifiant, la mesure de la viscosité est essentielle puisque la comparaison avec celle du lubrifiant usagé permet de vérifier ses propriétés d’écoulement mais aussi son éventuelle dilution, par du carburant par exemple.

Un des plus évidents facteurs qui peuvent avoir un effet sur le comportement rhéologique d'un lubrifiant est la température. Certains lubrifiants sont très sensibles à la température, et une relativement faible variation se traduira par une modification importante de la viscosité.

L’analyse de l'effet de la température sur la viscosité est essentielle dans l'évaluation des lubrifiants qui seront soumis à des variations de température en service ou à des transformations, telles que les huiles moteurs, graisses, et les adhésifs thermofusibles, [3,5].

Cet article propose d'étudier le comportement thermique des lubrifiants frais et usés, en tenant compte de la variation de la viscosité par rapport à la température.

2. NOTIONS DE THÉORIE

Le modèle rhéologique proposé pour les lubrifiants frais et usés est le modèle de Newton, pour lequel les tensions tangentielles dans le fluide sont proportionelles avec les gradients de vitesses:

dyduητ = (1)

Dans l’équation (1), la constante de proportionalité est la viscosité η, qui a une variation importante avec la température. Cette variation dépend de la nature chimique des huiles: la viscosité des huiles naphténiques diminue avec la température plus vite que celle des huiles paraffiniques. De ce point de vue, plusieurs lois de variation de la viscosité avec la température sont proposées, [3]: • Le modèle de Jarchov et Theissen:

ttB

e +−

⋅= 95

50

50ηη (2), où: η – la viscosité; η50 – la viscosité à 50 0C; B – paramètre adimensionel; t – température.

• Le modèle de Cameron:

tb

Ke += 95η (3), où: η – la viscosité; K – paramètre de viscosité; b – paramètre de température; t – température.

• Le modèle de Reynolds: ( )50

50−= tmeηη (4),

où: η – la viscosité; η50 – la viscosité à 50 0C; m – paramètre de température; t – température.

3. BANC D’ESSAI EXPÉRIMENTALE

Les viscosités des fluides se mesurent par

application de la loi de Newton à un type d’écoulement déterminé. Les appareils les plus utilisés sont les viscosimètres à capillaires et les viscosimètres à rotation. Dans les viscosimètres à rotation, le fluide étudié est cisaillé entre deux surfaces, l’une fixe et l’autre mobile en rotation.

La vitesse de déformation du fluide est reliée à la géométrie de l’appareillage et à la vitesse de rotation. La contrainte de cisaillement est déduite du couple appliqué. Il est ainsi possible de déterminer la viscosité d’une fluide.

Le banc d’essai expérimentale a été un viscosimètre Brookfield à cône-plateau, présenté dans la Figure 1. Le liquide est ici placé entre un cône et un disque, l’un tournant, l’autre immobile. L’avantage de cet appareil est que pour de grands angles d’ouverture du cône (Figure 2), la vitesse de déformation est constante dans tout l’entrefer.

Le viscosimètre est adapté pour l’acquisition numérique des données et offre la possibilité de déterminer la variation de la viscosité avec la température, [7].

Figure 1. Viscosimètre Brookfield à cône-plateau


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Figure 2. Géométrie des cônes utilisés

Afin d’obtenir des informations practiques concernant le comportement thermiques des lubrifiants avec divers degrées d’usure, on a testé trois types d’huiles roumaines, en état frais et usée (degré d’usure de 30%, 70% et 100%): − 10W40 – huile pour les moteurs à l’essance; − H46 – huile pour les cylindres hydrauliques; − M30 – huile pour les moteurs Diesel. Les propriétés physique et chimique des huiles testés sont présentées dans le Tableau 1, [8]. Tableau 1. Propriétés physique et chimique des huiles testés, [8]

HuileParamètre 10W40 H46 M30

Densité à 15°C 890 kg/m3 900 kg/m3 905 kg/m3

Viscosité à 100°C 14.0-16.3 cSt

6.5-8.9 cSt

9.4-12.5 cSt

Indice de viscosité 145 92 90 Point d’écoulement -30 0C -25 0C -21 0C

Point d’inflamabilité 215 0C 200 0C 230 0C

4. RÉSULTATS

Les rhéogrammes caractéristiques obtenues

avec le viscosimètre Brookfield, pour tout les huiles testés, sont présentées dans les Figures 3, 4 et 5.

Dans chaque figure, on a représenté la variation de la viscosité avec la température, pour quatre degrés d’usure de l’huile: 0% (huile frais), 30%, 70% et 100% (huile usé).

On peut observer que la viscosité baisse avec la température, ce qui est un comportement normale pour l’huile, mais, en plus, elle depend du degré d’usure de l’huile.

Figure 3. Variation de la viscosité avec la température pour l’huile 10W40

Figure 4. Variation de la viscosité avec la température pour l’huile H46

Figure 5. Variation de la viscosité avec la température pour l’huile M30

Les résultats numériques de la variation de

viscosité avec la température on été traités à l’aide de la méthode de l’analyse de régression [4], afin d’obtenir les valeurs des paramètres thermique des huiles, correspondants aux équations (2), (3) et (4).

Les résultats obtenus sont présentés dans les tableaux 2, 3 et 4.


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Tableau 2. Valeurs principales pour les paramètres thermiques de l’huile 10W40

Modèle de Jarchov et Theissen Paramètre Huile

η50, Pa⋅s B Coeff. de

corrélation Frais 0.0520 5.287 0.9989

Usé 30% 0.0446 5.426 0.9976 Usé 70% 0.0403 5.460 0.9978 Usé 100% 0.0354 5.478 0.9972

Modèle de Cameron Paramètre Huile K, Pa⋅s b, 0C Coeff. de

corrélation Frais 2.628⋅10-

4 766.67 0.9989

Usé 30% 1.963⋅10-

4 786.75 0.9976

Usé 70% 1.713⋅10-

4 791.71 0.9978

Usé 100% 1.478⋅10-

4 794.39 0.9972

Modèle de Reynolds Paramètre Huile

η50, Pa⋅s m, 0C-1 Coeff. de

corrélation Frais 0.0509 -0.0459 0.9988

Usé 30% 0.0435 -0.0473 0.9996 Usé 70% 0.0392 -0.0477 0.9996 Usé 100% 0.0344 -0.0478 0.9995

Tableau 3. Valeurs principales pour les paramètres thermiques de l’huile H46




Usé 30% 0.0227 6.177 0.9968 Usé 70% 0.0234 6.096 0.9951 Usé 100% 0.0213 6.294 0.9961



5 907.66 0.9972

Usé 30% 4.723⋅10-

5 895.71 0.9968

Usé 70% 5.264⋅10-

5 883.84 0.9951

Usé 100% 3.937⋅10-

5 912.59 0.9961




Usé 30% 0.0216 -0.0548 0.9993 Usé 70% 0.0223 -0.0539 0.9991 Usé 100% 0.0202 -0.0560 0.9993

Tableau 4. Valeurs principales pour les paramètres thermiques de l’huile M30




Usé 30% 0.0940 6.488 0.9993 Usé 70% 0.0918 6.314 0.9987 Usé 100% 0.0910 6.284 0.9988



4 954.05 0.9988

Usé 30% 1.429⋅10-

4 940.88 0.9993

Usé 70% 1.663⋅10-

4 915.58 0.9987

Usé 100% 1.698⋅10-

4 911.22 0.9988




Usé 30% 0.0877 -0.0582 0.9994 Usé 70% 0.0865 -0.0563 0.9997 Usé 100% 0.0857 -0.0561 0.9996 5. DISCUSSIONS ET CONCLUSIONS

Les informations concernant la viscosité des lubrifiants peuvent être considérées comme une « fenêtre » pour analyser les autres propriétés des fluides. La viscosité est toujour plus facile à mesurer que beaucoup d’autres propriétés des lubrifiants, en constituant un outil très important pour la caractérisation des fluides.

En analysant les donnés expérimentales présentés dans les tableaux 2, 3 et 4, on peut observer une importante tendance de diminution des valeurs de la viscosité avec le degré d’usure du lubrifiant. Pour tout les trois huiles analysés, on constate que la viscosité du fluid usé est plus petite que celle du fluide frais. Concernant la variation de la viscosité avec la température, on a proposé trois modèles: Jarchov et Theissen, Cameron et Reynolds.

Tous ces modèles sont convenables pour approximer cettes variations, mais le meilleure est le modèle de Reynolds.

Enfin, le principal résultat de cette recherche est une nouvelle méthodologie pour l'évaluation et la quantification de l'usure et de la durabilité des lubrifiants, en tenant compte de la variation de la viscosité du lubrifiant par rapport à la température.


69

RÉFÉRENCES [1] Ahlborn G.H., “Lubricant Barrier Film

Contaminated Ball Bearings - A Bearing Life Threat?”, Lubrication Engineering, 1979, volume 35, nr.12, pp. 677-686.

[2] Bolster R.N., “Removal of Fluid Contaminants by Surface Chemical Displacement. Suiface Contamination”. Londres : Plenum Press, 1979.

[3] Briant, J. et al. "Propriétés rhéologiques des lubrifiants", Édition Technip, 1985

[4] Crocker, D.C. "How to use regression analysis in quality control", American Society for Quality Control, Vol. IX, 1983

[5] Ram A., “High Shear Viscosimetry. Rheology. Theory and Applications”. Eirich F.R. New York, London: Academic Press, 1967. pp. 251-284.

[6] Ville F., “Pollution Solide dans les Lubrifiants, Indentation et Fatigue des Surfaces”, These de Doctorat: INSA Lyon, 16 Nov. 1998.

[7] *** Catalogue CAP 2000+ viscometer, www.brookfieldengineering.com/

[8] *** Catalogue pour les huiles SC ICERP SA Ploiesti, http://www.icerp.ro/fise/Lubricerp/Uleiuri

Quick Info Power Engineer - IT Automation

Digital automation for coal gasification plant Shanghai Coking Chemical Corporation and Emerson Process Management announced that Emerson had been selected to provide its PlantWeb digital plant architecture with Foundation fieldbus technology for the $375 million expansion of the coal gasification plant in Shanghai. The project has doubled the plant’s output of methanol and carbon monoxide to help meet the rapidly increasing need for methanol in the region. The expanded plant began operation in June 2008. The plant converts coal to synthesised gas, methanol, and carbon monoxide. The expansion project produces hourly 11,618 cubic metres of synthesised gas, 22,000 cubic metres of carbon monoxide, and 56 tons of methanol. The synthesised gas is supplied to customers in the Shanghai Chemical Industry Park, while the methanol and carbon monoxide are used as a chemical intermediate for acetic acid. “We selected Emerson’s PlantWeb architecture because it provides a simple digital architecture that can be easily configured to meet the complex requirements of our process,” said Mr. Guanghua Li, chief engineer for Shanghai Coking and Chemical Corporation. “The improved predictive capabilities and streamlined communications provided by PlantWeb technology will help us meet our high availability targets for the expanded plant. Emerson’s extensive experience in large project management was another factor in the selection process. We have already been very impressed with Emerson’s strong local engineering and support capability.” In addition to installing PlantWeb, Emerson’s contract includes project management, system integration, configuration, commission and start-up, and maintenance services. Emerson’s PlantWeb digital architecture delivers operational excellence by networking thousands of smart devices


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throughout plants, enabling optimum control, while continuously gathering diagnostics data that is used for asset optimisation, including predictive maintenance. Plant personnel use the data to correct potential equipment and process problems before they interrupt production. Shanghai Coking Chemical Corporation is a large comprehensive chemical company, which uses coal as its primary raw material. It is the largest producer of city coal gas in the Shanghai area, providing 50% of Shanghai’s gas demand with a current daily output of 3.2 million cubic metres. The company’s main products include 1.5m t/a coke, 800k t/a methanol and 360k t/a carbon monoxide. Its annual sales are more than $700 million. For more information, visit www.emersonprocess.com (source:http://www.engineerlive.com) Power Engineer - Renewable Energy

Solar solutions for thin-film generation DEK Solar has announced that its PV1200 photovoltaic metallisation platform is not only being deployed around the world to meet the challenges of silicon wafers but also, to meet the commercial challenges of thin-film substrates. DEK says it is driving the production of thin-film PV cells towards mass market adoption through a range of cost and productivity benefits. The emergence of new types of solar cells produced using thin-film technology presents solar manufacturers with a number of advantages including cost benefits against increasingly expensive silicon wafers.

For example, thin-film technology enables solar cells to be constructed on flexible substrates, opening up many new opportunities to embed solar power generation into diverse commercial applications. Working closely with influential producers, DEK has developed a range of metallization solutions for thin-film substrates. Processes include precision deposition of silver epoxy compounds for metallisation, as well as the application of other active and interconnect layers, using printing techniques similar to those already proven in bulk silicon solar cell production. “As the production of solar cells increases globally, producers need better and faster production technology, backed by shorter lead-times and customer support capable of supporting ongoing productivity,” explains DEK’s Alternative Energy Business Development Manager, Darren Brown. “Here at DEK Solar, we’ve already established world-class production values for companies building photovoltaic cells on silicon wafers and we’re delighted that we can now deliver the same opportunities to thin-film cell producers. Combined with leading-edge production technology, our global support infrastructure provides even the most progressive companies with the back-up they need to maximise throughput and yield. What’s more, I’m confident that our commitment to partnering with our customers will continue to optimise the production of thin-film solar cells for mass-market adoption into the future.” DEK’s PV1200 solar metallisation line delivers 1200 cells-per-hour throughput, six-sigma process rating, 12.5 micron resolution and advanced handling capabilities. For more information, visit www.deksolar.com (source:http://www.engineerlive.com)


71

ASPECTE PRIVIND PROIECTAREA OPTIMIZATĂ A ELEMENTULUI DE STRUCTURĂ TIP BRAŢ ARTICULAT

AL UNUI ROBOT RRR

Adrian Ghiorghe

Politehnica University of Bucharest, ROMANIA,Faculty of Engineering and Management of Technological Systems

e-mail : [email protected]

REZUMAT Optimizarea elementelor de structura ale robotilor industriali este esenţială in proiectarea modernă optimizată prin simularea cu element finit şi modificarea structurii în a obţine o structură cu o rigiditate maxima. Prin aplicarea algoritmului de optimizarea structurală şi topologică s-a urmărit determinarea valorilor optime pentru variabilele de proiectare în condiţiile reducerii de material în structura robotului. Optimizarea structurală prin MEF constă în realizarea modelului geometric parametrizat al ansamblului robotului, prin considerarea unor mărimi geometrice ca variabile de proiectare, impunerea unor condiţii restrictive asupra modelului şi stabilirea unei funcţii obiectiv a optimizării. Prin rulări succesive ale analizei prin MEF, sunt variate valorile variabilelor de proiectare şi sunt procesate variabilele de stare, pentru stabilirea fezabilităţii setului de variabile de proiectare, în vederea determinării unui set optim (minim) din punct de vedere al funcţiei obiectiv.

ABSTRACT Optimization of structural elements of industrial robots is essential in modern design optimized by finite element simulation and obtain a modification of the structure with maximum rigidity. By applying structural and topology optimization algorithm was intended to determine optimal values for design variables in terms of reducing material in the structure of the robot. Structural optimization is to achieve MEF parameterized geometrical model of the assembly robot, by considering some geometric sizes as design variables, imposing restrictive conditions on the model and establish an objective function to optimize. The runs of the FEM analysis, are different values of design variables and state variables are processed, to determine the feasibility set of design variables in order to determine an optimal set (minimum) in terms of objective function. KEYWORDS: structural optimization, robot, stiffness, frequency CUVINTE CHEIE: optimizare structurală, robot, rigiditate, frecvenţă

1. INTRODUCERE

Proiectarea optimizată a elementelor de structură ale unui robot industrial trebuie să corespundă unor criterii dimensionale, design(formă), material şi funcţionale impuse.

În proiectarea optimizată a structurii robotului inginerul proiectant trebuie să se ia în calcul câteva aspecte legate de abordarea temei impuse ţinând cont şi de solicitările la care va fi supusă structura robotului. Aici vor aparea câteva întrebări pe care proiectantul trebuie să şi le pună legate de rezistenţa elementul de structură la solicitările reale, dacă este supradimensionat, dacă materialul ales corespunde, deformaţia elementului de structură va depăşi limitele impuse, comportamentul braţelor acestuia corelat cu elementele din cuple de rotaţie ale structurii robotului.

Metodele moderne de proiectare optimizată ale unui

structuri de robot implică utilizarea programelor de proiectare asistată şi analiză cu elemente finite (CAD-FEM).

În cadrul programelor de analiză şi verificare ale elementelor de structură şi structurii complete a roboţilor industriali, analiza cu elemente finite a unui subansamblu sau a unui întreg ansamblu a devenit o necesitate în proiectarea modernă. Se poate realiza un model virtual al robotului cu elementele de structură care să poată fi optimizat prin program.

Problematica metodei ţine de raportarea structurii modelate pe calculator la o structură fizică de la care să se poată obţine unele rezultate privind comportarea statică, modală şi dinamică.


72

2. OPTIMIZAREA FORMEI CONSTRUCTIVE A ELEMENTELOR DE

STRUCTURĂ ŞI RESTRICŢIILE IMPUSE DE STRUCTURĂ ÎN URMA

ANALIZEI CU ELEMENT FINIT

Elementele de structură şi structura asamblată a robotului modelată pe calculator, într-o primă etapă, reprezintă aproximarea structurii fizice. În funcţie de rezultatele experimentale obţinute se modelează structura virtuală a elementelor de structură ale robotului până când se obţine o comportare aproape identică cu cea a structurii fizice. Stadiul actual al cercetărilor teoretice şi experimentale în vederea îmbunătăţirii construcţiei optimizate a elementelor de structură şi structurii complete a roboţilor, a relevat că principalele variabile de proiectare optimizată a structurilor sunt materialele noi care să înlocuiască materialele tradiţionale caracterizate de proprietăţi fizico-mecanice nesatisfăcătoare utilizate pentru elementele de structură şi modelarea optimizată a formei elemetelor de structură prin algoritmi şi programe de utilizare.

Pentru îmbunătăţirea comportării statice şi dinamice a structurii unui robot industrial precum şi a unui element de structură oarecare trebuie satisfăcute următoarele cerinţe:

- greutate minimă a structurii portante; - rigiditate statică maximă a elementelor de

structură; - săgeată minimă a elementului de execuţie (end-

effectorul); - frecvenţă de rezonanţă cât mai mare, în afara

domeniului de frecvenţe din mediul de lucru; - momente de inerţie minime, cu implicaţii asupra

săgeţii dinamice a end-effectorului. În analiza cu elemente finite a structurii unui robot

articulat se identifică câteva etape care ar trebui urmărite şi analizate rezultatele prin definirea elementelor discretizate; definirea proprietăţilor fizico-mecanice ale materialului elementelor de structură şi restricţiile impuse acestora, datorate elementelor de acţionare pentru subansamble prin introducerea restricţiilor în toate nodurile în care se presupune că avem contact între elementul conducător şi cel condus; calcularea matricii de rigiditate pentru structură; introducerea încărcărilor statice (forţe şi momente pe toate axele x, y, z), în nodurile care definesc legăturile între subansamble; analiza statică, prin determinarea deplasărilor şi tensiunilor care apar în structură;deplasările şi tensiunile pot fi corespunzătoare axelor x, y, z sau o compunere a acestora, iar în cazul tensiunilor se vor determina tensiunile principale şi globale; analiza modală prin determinarea frecvenţelor proprii şi a modurilor proprii de vibraţie; permite simularea comportării subansamblelor pentru toate

modurile proprii; în acest fel se pot stabili tipurile de moduri proprii care solicită structurile (torsionale sau de încovoiere) şi se pot trage concluzii legate de elementele de ranforsare care trebuie introduse pentru îmbunătăţirea comportării structurilor; analiza modală dă informaţii asupra frecvenţelor proprii şi modurilor proprii de vibraţie ale structurii, datorate forţelor de greutate, pentru structura considerată izolată de restul elementelor; optimizarea elementelor de structură pe baza analizei statice şi modale, prin introducerea de nervuri şi diafragme pentru zonele unde se constată deformaţii sau amplitudini mai mari ale modurilor proprii de vibraţie; analiza dinamică, care constă în introducerea în nodurile în care se consideră încărcarea statică, a unei forţe dinamice, distribuţia în mai multe noduri, care preiau încărcarea.

Figura 1. Optimizarea structurală în procesul de proiectare

În calculul analizei rigidităţii (Nakasone et al., 2006)

se bazează pe ecuaţia de rigiditate (1) prin discretizarea cu elemente triunghiulare finite şi calcularea matricii de rigiditate pentru structură (2), şi forţele (3):

(1)

(2)

(3)


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Se va propune pentru fiecare structură a mai multor variante de elemente de structură tip braţe prin plasarea unor nervuri sau diafragme pentru a se scadea greutatea cu o îmbunătăţire, creştere a rigidităţii elementului de structură având în vedere modelul experimental al robotului. Practic se va înregistrarea o deformaţiei obţinută experimental şi se va comparara ca ordin de mărime cu cea dată de analiza statică. După care se va analiza cauzele care contribuie la diferenţe între modelul experimental şi cel teoretic şi propuneri de reducere a acestora.

Prin reducerea masei structurii robotului, simultan cu creşterea rigidităţii statice sunt îmbunătăţite valorile frecvenţelor proprii care cresc.

Scopul este de a găsi cea mai bună utilizare a materialului pentru o structură supusă acţiunii unei forţe sau mai multor forţe distribuite. Din această perspectivă optimizarea topologică permite proiectarea elementelor de structură pentru obţinerea unei rigidităţi maxime.

Optimizarea topologică poate fi aplicată pentru un singur caz de încărcare sau pentru o încărcare multiplă, aplicată simultan. Pentru un număr k de cazuri de încărcare diferite, funcţia de greutate este definită:

ic

k

ii

iccc UwUUUF ∑

=

=1

21 ),...,,( , (4)

unde iw reprezintă greutatea structurii pentru cazul de

încărcare cu energia de complianţă structurală icU .

Funcţia care trebuie minimizată cU este înlocuită în

caz cu funcţia F .

3. ANALIZĂ ŞI REZULTATE

Primul pas al analizei cu elemente finite este crearea unui model CAD pentru structura completă a robotului Fanuc LR Mate 100iB ţinând cont şi de restricţiile impuse în articulaţii folosind softul de modelare 3D, SolidWorks 2008.

În scopul de a analiza comportarea statică, analiza modală prin determinarea frecvenţelor proprii şi a modurilor proprii de vibraţie folosind un soft Ansys Workbench 10.0 de analiză cu element finit.

Pentru analiza FEM a structurii robotului am considerat ca date de intrare după cum urmează: forţe distribuite pe Ox, Oy, Oz la o încărcare a gripperului de 50kg~490N şi o distribuţie de temperatură în zona de lucru de 50°C. Structura analizată static cuprinde: deformare totală şi deplasarea pe direcţiile de stres principale şi echivalente (von Mises), stres, precum şi modurile de frecvenţă în gamă a structurii robotului. Rezultatele comparative ale limitelor maxime atinse în termeni de deformare sunt prezentate în tabelul de mai jos. Pasul final de optimizare depinde de ceea ce trebuie să fie îmbunătăţită, care va stabili parametrii pentru a

fi analizate. Analiza de parametri, cum ar fi: deformare, rigiditate sau frecvenţă trebuie să fie luate în considerare în scopul de a optimiza modelul de robot. Parameter Total

deformationX axis

deformation

Y axis deformation

Z axis deformation

Mimimum 0 -0.068 -0.009 -0.323 Maximum

0.374 0.110 0.265 0.054

Tab. 1. Deformaţiile totale şi după direcţiile Ox,Oy,Oz Principal stress 1xe8 Pa

Mimimum Principal stress

Middle Principal stress

Maximum Principal stress

Equivalent stress

Mimimum -9.894 -4.054 -3.413 0.691 Maximum

0.167 0.769 2.468 6.223

Tab. 2. Deformaţiile principale la încărcare Frequency Modes

in Range 1st 2nd 3rd 4th

Structure only frequency (Hz)

51.57 58.95 153.24 187.65

Maxim 0.197

0.216 0.211 0.270

Tab. 3. Domeniul modurilor de frecvenţă

Figura 2. Geometria structurii robotului Fanuc

Figura 3. Discretizarea(mesh) structurii robotului

Figura 4. Deformaţia totală a structurii robotului


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Figura 5. Deformaţia pe directia axei X

Figura 6. Deformaţia pe directia axei Y

Figura 7. Deformaţia pe directia axei Z

Figura 8. Solicitarea maximă la stres

Figura 9. Solicitarea medie la stres

Figura 10. Solicitarea minimă la stres şi încărcarea echivalentă(von-Mises)

Figura 11. 1-ul domeniu al frecvenţelor proprii şi al modurilor proprii de vibraţie

Figura 12. Al 2-lea domeniu al frecvenţelor proprii şi

al modurilor proprii de vibraţie Figura 13. Al 3-lea domeniu al frecvenţelor proprii şi

al modurilor proprii de vibraţie

Figura 14. Al 4-lea domeniu al frecvenţelor proprii şi

al modurilor proprii de vibraţie

După modelarea solidă în modulul CATIA Part Design a braţului robotului se consideră a avea un material aliaj aluminiu de tipul 7079 cu următoarele proprietăţi fizice, importante în decursul analizei: modulul lui Young (72000 N/mm2), coeficientul lui Poisson (0.33), densitatea (0.0027 g/m3), coeficientul de dilatare termică (2.5×10-5

K), rezistenţa admisibilă (27000 N/mm2). Pentru a optimiza un element de structură prin

analiza statică s-a izolat braţul robotului la care se va aplica o încărcare statică cu forta=490N pe toate cele trei direcţii x, y, z. Braţul în urma materialului ales are o masa=3.55879 kg, tipul mesh=solid standard, număr de elemente: 63152, număr de noduri: 100181, dimensiunea elementului=5.4833 mm, toleranţa=0.27416 mm.


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În figura 15 este afişat rezultatele încărcării printr-o imagine Von Mises Stress, dar pot fi obţinute şi altele (Deformation, Principal Stress şi Precision), corespunzătoare calculului modelului de braţ considerat, alături de aceste ferestre, este prezentată şi paleta de culori care însoţeşte rezultatul – imagine Von Mises. Valorile cele mai mici ale tensiunilor se află în partea de jos a paletei, cele maxime în partea de sus a acesteia, dar fereastra de dialog conţine şi valorile explicite, în zona Extrema Values. Culorile albastre şi bleu indică tensiuni scăzute, iar culorile galben spre roşu tensiuni ridicate.

Figura 15: Rezultate Von Mises echivalent pe x,y,z

Figura 16. Rezultate Von Mises echivalent pe x,y,z a unor variante de braţe propuse

În figura 16 este afişat rezultatele încărcării a mai multor variante de braţe propuse pentru a îmbunătăţii comportarea statică şi cele două tabele tab.4 şi tab.5 cu valorile găsite în urma calcului cu element finit. Se va alege prima variantă pentru că s-a comportat mai bine şi din punct de vedere al formei.

CONCLUZII Cercetările efectuate au vizat:reducerea greutăţii

structurii; minimizarea deformaţiei elementelor de structură după direcţia Ox,Oy,Oz în vederea îmbunătăţirii rigidităţii;studiul efectelor optimizării structurale, în condiţii de solicitare statică, asupra comportării dinamice a ansamblului robotului.

Au fost stabilite două strategii de optimizare: optimizarea ansamblului din punct de vedere al rigidităţii şi optimizarea ansamblului din punct de vedere al greutăţii structurii şi a braţului robotului.

Rezultate fig. 15

Tipul Minim Localizarea Max Localizarea

Stres axa X von Mises Stress

0.703244 N/m^2

(-10.6165 mm, -67.8818 mm, 0 mm)

3.97268e+006 N/m^2

(-42.4908 mm, 76.2738 mm, -64.1056 mm)

Deplasări axa X

Rezultatele deplasărilor

0 mm (50.1333 mm, 6.13936e-015 mm, -64.5175 mm)

0.0111476 mm (-2.71822 mm, 303.932 mm, -24.13 mm)

Stres axa Y von Mises Stress

5.49144 N/m^2

(43.3419 mm, -51.2213 mm, 0 mm)

1.62343e+007 N/m^2

(-1.97137 mm, 71.916 mm, -24.13 mm)


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Deplasări axa Y


0 mm (50.1333 mm, 6.13936e-015 mm, -64.5175 mm)

0.0585494 mm (2.71822 mm, 303.932 mm, -24.13 mm)

Stres axa Z von Mises Stress

6.27877 N/m^2

(43.3419 mm, -51.2213 mm, 0 mm)

1.63821e+007 N/m^2

(-1.97137 mm, 71.916 mm, -24.13 mm)

Deplasări axa Z


0 mm (50.1333 mm, 6.13936e-015 mm, -64.5175 mm)

0.0601608 mm (2.71822 mm, 303.932 mm, -24.13 mm)

Tab. 4. Rezultate Von Mises echivalente pe x,y,z

Rezultate fig. 16

Tipul Minim Localizarea Max Localizarea

Stres axa X von Mises Stress

16.5776 N/m^2

(44.7779 mm, -50.2875 mm, 76 mm)

1.71093e+007 N/m^2

(58.9497 mm, 60.588 mm, 49.1376 mm)

Deplasări axa X


0 mm (62.7 mm, 0 mm, 29.01 mm)

0.0633982 mm (3.05937e-014 mm, 304 mm, 65.5 mm)

Stres axa Y von Mises Stress

1.73899 N/m^2

(-18.5555 mm, -66.4582 mm, 73 mm)

1.59826e+006 N/m^2

(58.9497 mm, 60.588 mm, 49.1376 mm)

Deplasări axa Y


0 mm (62.7 mm, 0 mm, 29.01 mm)

0.00483607 mm (3.05937e-014 mm, 304 mm, 65.5 mm)

Stres axa Z von Mises Stress

1.07031 N/m^2

(-2.88942 mm, -68.9395 mm, 76 mm)

3.3744e+006 N/m^2

(58.9497 mm, 60.588 mm, 49.1376 mm)

Deplasări axa Z


0 mm (62.7 mm, 0 mm, 29.01 mm)

0.010182 mm (-2.82614 mm, 303.926 mm, 65.5 mm)

Tab. 5 : Rezultate Von Mises echivalent pe x,y,z şi deplasările a unei variante propuse de braţ

REFERINŢE [1]. Dr. Jürgen Sauter, Boris Lauber, Pascal Häußler, Dirk Vieker -Structural Optimization – Integration and Gaps in Workflows of Numerical Simulation Processes,NAFEMS Seminar: „Integration of Numerical Simulation into the Development Process, November 17 - 18, 2003 Wiesbaden, Germany. [2]. Meske, R./Mulfinger, F./Warmuth, O./NAFEMS Seminar "Modellieren von Baugruppen und Verbindungen für FE Berechnungen", "Topology and Shape Optimization of Components and Systems with Contact Boundary" Conditions/24.-25.April2002,Wiesbaden [3]. Sauter, J./Fricke, H./Güngör, Z./Himmler,G./Hougardy, P./Lauber, B./Müller, O./Neithardt, W./Schirrmacher, R./Internationaler "Integrierte Topologie- und Gestaltoptimierung im virtuellen Produktentstehungsprozess" –Einbindung in die iViP Architektur und industrielle AnwendungVDI-Kongress/14.-15. September 2000/Würzburg [4]. Bakhtiary, N; Allinger, P; Friedrich, M; Mulfinger, F; Sauter, J; Müller, O; Puchinger, M. “A new Approach for Sizing, Shape and Topology Optimization”, SAE International Congress and Exposition 1996, 26.-29. February 1996, Detroit/Michigan, USA. [5]. Müller, O; Albers, A; Sauter, J; Allinger, P. “Topology Optimization of Large Real World Structures, NAFEMS World Congress 1999”, 26.-28. April 1999, Newport (Rhode Island),USA. [6]. Dorin, Al., Chiriţoiu, R., ”Analysis of the articulated stuctures of industrial robots using finite element method”, 1998, TCMM nr. 33, Ed. Tehnică, Bucureşti, ISBN 973-31-1238-0, pag.283-288;

[7]. Dorin, Al., Chiriţoiu, R., ”Optimizarea topologică prin metoda elementelor finite a structurilor articulate ale roboţilor industriali”, Construcţia de maşini, 2000 (52), nr,9. [8]. Dorin, Al., Chiriţoiu, R., ”Proiectarea parametrică a elementelor de structură ale roboţilor industriali prin metoda elementelor finite”, Conferinţa ştiinţifică TEHNOMUS, Ediţia a-X-a, 28-29 mai 1999, Universitatea “Ştefan cel Mare” din SUCEAVA. [9]. Dorin, Al., Predincea, N., Chiriţoiu, R., ”Soluţii constructive pentru braţele de roboţi”, Conferinţa ştiinţifică TEHNOMUS, Ediţia a-IX-a, 30-31 mai 1997, Universitatea “Ştefan cel Mare” din SUCEAVA. [10]. Ispas, C., Pupăză, C., Dogariu, C., ”Cercetări experimentale asupra structurii montanţilor maşinilor orizontale de alezat şi frezat”, Conferinţa Naţională de maşini-unelte, 1986, Bucureşti. [11]. Ispas, C., Dogariu, C., Pupăză, C., Zapciu, M., Mohora, C., Bălan, E., ”Studii teoretice şi experimentale privind deformaţiile statice ale elementelor de structură din ansamblul maşinilor-unelte”, Conferinţa Naţională de maşini-unelte, 1986, Bucureşti. [12]. Blumenfeld, M., ”Introducere în metoda elementelor finite”, Editura Tehnică, Bucureşti, 1995; [13]. Alamoreanu, E., ”Metoda elementelor finite şi elementelor de frontieră”, Universitatea POLITEHNICA din Bucureşti (litografiată), 1995; [14]. Olaru, A., Chiriţoiu, R., Mihai, N., ”Dinamica elementelor, sistemelor şi structurilor utilizate la roboţi şi manipulatoare”, (Lucrări de cercetare experimentală, modelare şi simulare), Universitatea POLITEHNICA din Bucureşti, 1997.


77

INOVAREA ÎN CADRUL SISTEMELOR COMPLEXE DE PRODUCŢIE

Radu Popescu

INCE - CEIS, ROMANIA, [email protected]

REZUMAT Articolul se preocupa de procesul inovării în cadrul sistemelor complexe de produse (S.C.P.). Acestea au un înalt conţinut de cunoaştere şi deci un rol crucial în Economia Cunoaşterii. Interacţia dintre inovarea de produs şi inovarea de proces este similară cu interacţia dintre inovarea de componente şi inovarea de arhitectură . ABSTRACT The paper analyses the proces of inovation in the field of Product Complex Systems (PCS).These systems have a high content of knowledge and an important place in the Knowledge Economy. Interaction between product and process inovation has similarities with the interaction between mechanical parts and that of firm architecture. KEYWORDS: inovation, Product Complex Systems, process, product CUVINTE CHEIE: inovare, sisteme complexe de producţie, proces, produs 1. INTRODUCERE

Vom analiza caracteristicile procesului de inovare

cu particularizari pentru diverse domenii ale construcţiei de maşini. Subliniem ca valabilitatea afirmaţiilor se extinde şi asupra altor domenii industriale. Se consideră patru factori cu influenţă decisivă asupra procesului de inovare. 1. Accesibilitatea resurselor ce se pot aloca inovării. 2. Capacitatea organizatorică de a conduce procesul

de inovare. 3. Ocazia de a inova . 4. Stimulentele pentru a inova.

Primii doi factori vizează direct inovarea la nivel de firmă. Ultimii doi reflectă mediul din cadrul firmei cu activitate de inovare.

Accesibilitatea resurselor pe care o firmă le alocă pentru inovare este corelată cu nivelul investiţiilor în domeniul C-D, numărul de cercetători şi ingineri, nivelul cunoaşterii tehnologice şi organizaţionale acumulate şi extinderea relaţiilor dintre firme. Este decisivă capacitatea unei organizaţii de a aprecia limitele până la care poate să-şi solicite resursele financiare şi umane şi poate gestiona generarea, acumularea şi integrarea cunoaşterii adecvate. Variaţia capacităţii organizaţiilor de a gestiona procesul de inovare este studiată amplu. Numeroşi cercetători au iniţiat studii care au investigat diverşi factori ce indică această variaţie.

Stimulentele şi oportunităţile pentru a inova sunt influenţate de politica guvernamentală, structura industriei, atractivitatea pieţelor şi eficienţa sistemului de protecţie a proprietăţii intelectuale, precum şi de constrângerile instituţionale.

Este din ce în ce mai recunoscut că diferenţele în natura produselor (de exemplu : bunuri de consum versus bunuri industriale sau bunuri simple versus sisteme complexe de produse), afectează în mod semnificativ o parte sau toţi aceşti factori.

Ne vom preocupa de procesul inovării în cadrul sistemelor complexe de produse (S.C.P.). Acestea au un înalt conţinut de cunoaştere şi deci un rol crucial în Economia Cunoaşterii. Efectele constrângerilor instituţionale asupra acestor procese există. Tipul de cunoaştere şi capabilităţi pentru a fi competitivi în (C.P.S.) – există şi sunt necesare. 2. PROCESUL DE INOVARE ŞI MEDIUL INSTITUŢIONAL PENTRU S.C.P

Cercetările privind investiţiile şi inovarea în domeniul industrial s-au concentrat pe modelele de inovare din industriile cu producţie de masă, Rothwell (1992) modelul ciclului de viaţă al industriei (Waterback 1994) şi modelul interactiv produs şi proces de inovare Pisano 1996).


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Procesului de inovare asociat cu S.C.P. i s-a acordat o atenţie mai redusă, deşi vizează bunuri care au o valoare adăugată înaltă şi sunt bunuri de capital de un nivel tehnic şi tehnologic deosebit de înalt. Aceste produse, reţele sau utilaje pentru care producţia se realizează în loturi mici sau chiar unicat, sunt menite să satisfacă necesităţile unor utilizatori individuali, reprezentaţi deseori de firme mari (Hobday 1997).

Exemple clasice sunt: simulatoarele de zbor, echipamentele din industria aeronautică, reţelele de telecomunicaţii, sisteme de transport pe calea ferată fără roţi, pe baza fenomenului levitaţiei magnetice (sistemul MAGLEV este realizat în Germania şi pus in prezent în exploatare în China), centrale nucleare livrate la cheie, sistemele de sateliţi, maşinile unelte grele prevăzute cu comandă numerică (MUCN), echipamentele grele pentru industria chimică şi petrochimică etc.

S.C.P. urmează un model diferit de evoluţie faţă de cel descris în general în ciclul de viaţă al produsului şi prin urmare necesită un set diferit de capacităţi.

Se pare că interacţia dintre inovarea de produs şi inovarea de proces este similară cu interacţia dintre inovarea de componente şi inovarea de arhitectură de-a lungul timpului. Aceasta permite tipizarea, dezvoltarea şi comercializarea S.C.P.

În cazul sectorului telecomunicaţiilor, capabilităţile esenţiale şi factorii de succes al firmei de telecomunicaţii, se află în domeniul standardelor tehnice, a proiectării şi integrării sistemelor, unde generaţiile de produse sunt fabricate dar şi înlocuite rapid. Cu toate stimulentele şi oportunităţile pentru a investi şi inova, firmele sunt afectate de mari provocări, nu doar de natura schimburilor tehnologice şi a cererilor pieţei dar şi de mediul instituţional în care aceasta este localizată.

Havis şi North (1971) arătau că firma este o entitate economică care acţionează în cadrul unui set de reguli politice, sociale şi legale de bază deferite drept cadrul instituţional al societăţii. Acest cadru instituţional stabileşte bazele pentru producţie, distribuţie şi schimb ca stimulente şi constrângeri pentru a reglmenta şi regla activităţile economice. În timpul perioadelor de prosperitate, cadrul instituţional poate afecta modelul viitor al inovării în termeni de noi capabilităţi, care oferă superioritate faţă de sistemul tehnic existent.

Cercetările arată că dezvoltarea S.C.P., în timp, generează schimbări tehnologice corelate de-a lungul unei căi de dezvoltare specifice. În aceste industrii, reglementările provind concurenţa şi circumstanţele tehnice pot influenţa stabilirea standardelor industriale.

Odată ce un standard devine larg utilizat este dificil ca tehnologiile alternative să fie acceptate deoarece cumpărătorii sistemelor complexe de produse au investit sume mari de bani (costuri

scufundate) în tehnologii cu ciclu lung de operare (deci în activitate durabilă).Aceasta însemnă că un complex produs - sistem care construieşte pe un standard de proiectare dominant poate să aibă o bază largă de utilizatori.

În acest fel producătorii sistemului beneficiază de venituri crescătoare. Prin contrast, înainte ca un standard aflat în competiţie, să poată fi larg adoptat, infrastructura existentă în funcţiune trebuie să fie dezmembrată, ceea ce implică o barieră de intrare greu de depăşit. La nivelul unei firme, schimbarea tehnologică rapidă şi creşterea profunzimii cunoaşterii tehnologice în ultimele decenii au generat creşterea complexităţii tehnologice în aproape toate sectoarele, dar mai ales în S.C.P.

În consecinţă, datorită fondurilor necesare şi riscurilor majore, tot mai puţine organizaţii au capabilităţile sau voinţa să acopere toate domeniile. Întreprinderile preferă să acceseze noua cunoaştere de la surse externe şi să inoveze prin asimilarea şi adaptarea cunoaşterii externe.

Nevoia de a integra cunoaşterea externă şi cunoaşterea internă, de a colabora cu alte organizaţii, are implicaţii majore pentru structura organizatorică a firmei (de exemplu: se trece de la structura funcţională la structura pe proiecte sau la o organizaţie a învăţării). Se extinde astfel învăţarea înainte de acţiune cât şi învăţarea în procesul muncii, precum şi cea de construire a unor capabilităţi (concentrarea pe capabilitate dinamică). Succesul în realizarea acestor schimbări nu mai este rezultatul oferirii şi furnizării unui număr de factori discreţi cum ar fi bunele abilităţi, competenţă, management de proiect, tehnici moderne de cercetări de marketing sau o puternică orientare pe necesităţile clientului.

În aceste cazuri, succesul rezultă din abilitatea de a gestiona şi din sensibilitatea atât la schimbările tehnologice cât şi la cerinţele pieţei.

Un studiu mai aprofundat ( pentru aeronautică ) arată că noţiuni simple, cum ar fi competenţele de bază şi de integrarea verticală ( care sunt generate de către industriile cu producţie de masă tradiţionale) pot fi inadecvate pentru firme. Ele pot dăuna abilităţii firmei de a stăpâni dinamica evolutivă a sistemelor complexe de produse.

Odată stabilit contextul mai larg care cuprinde industriile S.C.P. ne vom concentra pe secţiunea care urmează pe problema accesibilităţii resurselor şi capabilităţii firmei de a inova în aceste industrii. 3. ACCESIBILITATEA RESURSELOR ŞI CAPABILITĂŢILE DE INOVARE

Accesibilitatea resurselor şi capacitatea de

inovare în S.C.P. sunt prin natura lor evolutive. Cercetătorii identifică trei aspecte ale procesului de


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inovare în S.C.P. care pot fi atribuite dinamicii acestora:

- interdependenţa tehnică dintre componentele şi subsistemele sistemului;

- interdependenţa dintre funcţiile unei organizaţii;

- sprijinul pe relaţiile externe; Vom studia impactul celor trei aspecte asupra

procesului de inovare în cadrul întreprinderilor. Interdependenţa tehnică dintre

componente/subsisteme. Interdependenţa tehnică dintre subsisteme

afirmă că: există o interacţie biunivocă complexă între rezolvarea problemelor tehnice şi definirea cerinţelor funcţionale ale subsistemelor, care poate produce dificultăţile tehnice iniţiale. Deseori, aceasta implică redefinirea soluţiei tehnice alese.

Puternica interdependenţă de sistem arată că, orice schimbare care afectează sistemul poate fi introdusă doar gradual, deoarece există un mare număr şi un volum mare de componente implicate, precum şi un număr însemnat de încercări care trebuie efectuate. Natura iterativă şi diversă a proiectării sistemelor complexe de produse poate fi ilustrată în cazul proiectării motoarelor de aeronave. Pentru a dezvolta motoarele aeronavelor civile, efortul investiţional este de un miliard de dolari şi 10 ÷ 12 ani până se obţine profit, deci peste un deceniu de cash flow negativ .

Cerinţele pieţei există în cadrul unui context social de acreditare a viabilităţii aeriene : procesul internaţional care asigură avioanelor şi motoarelor lor în privinţa siguranţei de zbor. Pentru a obţine acreditarea pentru zboruri transatlantice, un avion trebuie să fie capabil să realizeze zboruri în deplină siguranţă şi să aterizeze în bune condiţii chiar dacă a pierdut nu motor la jumatatea drumului.

Pentru a îndeplini aceste cerinţe este necesar ca peste 40.000 componente şi subsisteme ale motorului să funcţioneze împreună corect, să aibă o greutate acceptabilă (suficient de mică), un consum de combustibil, emisiune de noxe, poluare, nivel de zgomot, dimensiuni, cost, temperatură, nivel al vibraţiilor, reduse, viteză mare precum şi capacitatea de a face faţă situaţiilor care apar (cum ar fi o pasăre care loveşte paletele ventilatoarelor şi le distruge).

Proiectarea aerospaţială este un proces multi nivel realizat ierahic.La fiecare nivel, problema care cere o soluţie funcţională care este rezolvată şi calificată prin studiu.

Acest proces de a coborâ problemele în jos pe ierarhie, de a le rezolva şi apoi de a transmite soluţiile în sus implică posibilitatea pentru a exploda costurile reproiectării. Astfel, distrugurea unei palete a ventilatorului la ultimul studiu al testării poate să coste 100 de milioane dolari şi să implice reproiectarea aproape de la început.

Interdependenţa dintre funcţiile organizaţiei este accentuată de creşterea

Interdependenţa dintre funcţiile organizaţiei. volumului şi profunziunii cunoaşterii, de necesitatea şi nevoia de a înţelege piaţa tot atât de bine ca şi cerinţele tehnice din timpul proiectării şi dezvoltării procesului: 2005. Aceasta presupune ca, schimbările de sistem în ciuda faptului că sunt viabile din punct de vedere tehnic, să nu fie posibile datorită inerţiei organizaţionale (de exemplu: rezistenţa la schimbare) şi a constrângerilor (structura organizatorică neadecvată).

În cazul unei companii multinaţionale de telecomunicaţii, inerţia constrângerilor are efecte asupra orientării strategice a firmei.

- Orientarea anterioară: producţia de masă a sistemului de schimb şi a telefoniei mobile;

- Noua decizie: mişcare strategică importantă; de la a fi în principal o afacere bazată pe fabricaţie la a deveni un furnizor de soluţii, pornind de la consultarea clientului, specificarea nevoilor, la proiectarea sistemului, instalarea sistemelor, servicii post-vânzare şi modernizarea sistemelor.

Pentru a-şi atinge obiectivul strategic firma trebuie să facă un efort investiţional în domenii de vârf: să achiziţioneze noi capabilităţi tehnice în domeniul I.T. şi al afacerilor legate de servicii.

Aceasta implica şi schimbări majore în modul în care era organizată munca în cadrul organizaţiei. Echipele multifuncţionale şi interfuncţionale urmau să fie organizate pentru a putea să înlocuiască actuala structură organizatorică, bazată pe o disciplină ierarhică strictă. Acum, fiecare echipă devenea responsabilă pentru un anumit client, pe întreg ciclul dezvoltării unui anumit produs.

Noua organizare a muncii a devenit radical diferită de procesul existent anterior al afacerilor firmei, în care fiecare stadiu era în responsabilitatea unui grup funcţional sau departament iar munca era îndeplinită într-o manieră secvenţială, etapizată.

Răspunsul angajaţilor a fost diferit: - departamentele de marketing şi dezvoltarea

afacerilor au arătat un deosebit entuziasm şi un interes viu.

- departamentul tehnic şi C-D au manifestat rezistenţă.

În locul unor schimbări radicale ale structurii organizatorice, până la cea a organizaţiei complet bazate pe proces, care ar fi fost mai adecvate pentru ducerea la bun sfârşit a tipului de sarcini conţinute de planul strategic, firma a decis să formeze o echipă pilot, care să experimenteze noua structură mai întâi la o scară redusă şi să o extindă gradat.

Între timp restul firmei a fost antrenat şi pregătit pentru implementarea noii structuri la scară largă, într-un stadiu ulterior.


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Directorul coordonator a explicat raţionamentul din spatele acestei strategii incrementale astfel:’’ În loc să vindem doar cutii, suntem hotărâţi să ne deplasăm spre oferirea de soluţii mai bune şi mai complete clienţilor noştri.

Aceasta este direcţia industriei de telecomunicaţii. Totuşi, nu putem schimba organizaţia peste noapte. Pentru unele lucruri trebuie să ne bazăm pe procesele şi produse existente, în vederea generării venitului. Schimbarea trebuie să fie realizată, dar gradat.’’ CONCLUZII

Procesului de inovare asociat cu S.C.P. i s-a

acordat o atenţie mai redusă, deşi vizează bunuri care au o valoare adăugată înaltă şi sunt bunuri de capital de un nivel tehnic şi tehnologic deosebit de înalt.

Aceste produse, reţele sau utilaje pentru care producţia se realizează în loturi mici sau chiar unicat, sunt menite să satisfacă necesităţile unor utilizatori individuali, reprezentaţi deseori de firme mari, care realizează un volum important de investiţii.

SPC prezintă un nivel înalt sinergii datorate complexităţii tehnice şi manageriale.

BIBLIOGRAFIE 1 Bragg, A., Bragg, M., ”Developing new business ideas”, Prentice Hall London, 2005. 2. Ciumara, M., “Investiţie şi corupţie în economia de tranziţie a României”, Al cincelea simpozion internaţional “Investiţiile şi relansarea economică.”Bucureşti, 2003 3. Cooper, L., ”Leadership and Management in the 21st Century”, Oxford University Press, 2005. 4. Curtin, T., Hyman, D., Husein, N., ”Managing a Crisis”, Polgrave Macmilton, London, 2005. 5. Popescu, R., Stoica, M., “Provocări ale Managementului în secolul XXI”, Germania, Bochum, Proceedings, 2004.

Quick Info

12th IEEE/IFIP Network Operations and Management Symposium Osaka, Japan 19-23 April 2010 NOMS 2010 will offer four types of sessions: technical, application, poster, and panel sessions. Technical sessions will present high-quality papers on the latest research results in the network operations and management area. Application sessions will include papers focusing on the experience in IT and telecommunications industries, such as service providers, OSS vendors, and equipment manufacturers. The scope here includes customer requirements, management system implementations, and business practices. Poster sessions provide an insight into work-in-progress. Panel sessions will focus on business implications, market trends, and emerging applications with panelists who are the technology and business leaders. IEEE is the world’s largest professional association advancing innovation and technological excellence for the benefit of humanity. IEEE and its members inspire a global community to innovate for a better tomorrow through its highly cited publications, conferences, technology standards, and professional and educational activities. IEEE is the trusted “voice” for engineering, computing and technology information around the globe.

IEEE Quick Facts IEEE has:

more than 375,000 members in more than 160 countries; 45 percent of whom are from outside the United States

more than 80,000 student members 329 sections in ten geographic regions

worldwide 1,860 chapters that unite local members with

similar technical interests 1,789 student branches in 80 countries 483 student branch chapters at colleges and

universities 390 affinity groups -- IEEE Affinity Groups are non-technical sub-units of one or more Sections or a Council. The Affinity Group patent entities are Consultants' Network, Graduates of the Last Decade (GOLD), Women in Engineering (WIE) and Life Members (LM).


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SPRIJINIREA PE LEGĂTURILE EXTERNE ÎN PROMOVAREA INOVĂRII

Radu Popescu

INCE - CEIS, ROMANIA, [email protected]

REZUMAT Necesitatea valorificării rezultatelor externe este impusă de către schimbările tehnologice rapide. Firmele trebuie să echilibreze tot mai mult opţiunea între a menţine competenţele necesare pentru realizarea S.C.P.(sistemelor complexe de produse) şi prevenirea efectului de răspândire, atunci când modelul tehnologic se schimbă. ABSTRACT External results assesment is a necesity requested, by the speed of technological changes. Companies have to balance between two options: To maintain the necessary competencies in order to build Product Complex Systems and to prevent the lack of concentration and specialisation when the technological model changes. KEYWORDS: inovation, capitalization, Product Complex Systems, external results CUVINTE CHEIE: inovare, valorificare, sisteme complexe de producţie, rezultate externe 1. INTRODUCERE

Firmele mari, cu tradiţie, adoptă o strategie de creştere a eficienţei dinamice şi reducerii eficienţei statice prin focalizarea asupra capabilităţii integrative şi a tehnologiilor componente decisive, în paralel cu aportul de alte tehnologii noi, preluate de la I.M.M. specializate pe tehnică de vârf. Această decizie strategică presupune şi duce în acelaţi timp la interacţii mai strâse între firmele mari şi cele mici.

De altminteri, pe plan mondial se constată că, sursa de inovare provine tot mai mult de la firme mici de înaltă tehnologie, în vreme ce firmele mari preiau rolul de a asimila rezultatele inovării tehnologice.

De exemplu: I.M.M. încep treptat să acţioneze ca specialişti orientaţi spre cercetare şi devin tot mai responsabile pentru promovarea cunoaşterii în domenii de vârf (biotehnologie, nanotehnologii). Marile firme de procesare utilizează aceste cercetări pentru a dezvolta un domeniu vast de noi produse dar nu şi-au dezvoltat ele înşile producţia şi publicaţiile de specialitate.

Astfel, o mare firmă lider mondial pe piaţă în domeniul energiei şi infrastructurii de transport, oferă date referitoare la legăturile între firme pentru a livra proiecte importante.

Compania este organizată în 6 sectoare: energie, trasmiterea şi distribuţia acesteia, transport, industrie, marină, contractare.

Ea oferă un domeniu complex de sisteme,

componente şi servicii care acoperă atât proiectarea cât şi fabricaţia, dar şi contractele de mentenanţă pe termen lung. Firma are o experienţă vastă şi competenţe/ priceperi în sistemele integrate şi managementul proiectelor livrate la cheie.

Firma avea în 1998 / 1999 o cifră de afaceri ( C.A.) de peste 14 miliarde de dolari şi 114.000 salariaţi în 60 ţări. În Marea Britanie este leader pentru energie şi căi ferate (engineering, cu un nivel al exportului de 40% ).

O caracteristică care se conturează tot mai clar la proiectelor de export : există un număr mare de subcontractanţi şi furnizori cu care filialele au înţelegeri de colaborare. Aceste relaţii de colaborare au contribuit la creşterea valorii adăugate.

Multe colaborări sunt firme mici neimplicate în export direct. Acest tip de colaborare între firme mici şi firme mari este eficient pentru că ele au bunuri şi capabilităţi complementare. În vreme ce firmele mari au puterea bunurilor şi capabilităţilor pentru a licita pentru mari proiecte internaţionale, care sunt spijinite de către agenţiile de credit pentru export, firmele mici contribuie şi ele şi beneficiază de implementarea şi realizarea acestor proiecte, furnizând expertiză în ariile în care sunt specializate.


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În concluzie: traiectoriile tehnologice care evoluează, se dezvoltă împreună prin acumularea înţelegerii şi învăţării la nivel individual şi intra respectiv interorganizaţional.

De altfel, acest proces de învăţare tinde să fie gradual şi să urmeze calea imprimată de activităţile anterioare.

Noţiunea de dependenţă de calea aleasă explică faptul că activităţile anterioare ale firmei şi rutinele existente pot constrânge activitatea ei ulterioară (viitoare). Datorită complexităţii şi aspectului tacit al unor astfel de rutine şi componente acestea sunt dificil de imitat şi astfel contribuie la tezaurul de competenţe şi capabilităţi distinctive al firmei.

Setul total diferit de constrângeri organizaţionale specific fostelor ţări socialiste, Rusia şi China, va afecta procesul de inovare şi în particular cel al sistemelor complexe de produse. În ţările cu o economie de piaţă consolidată firmele pot să-şi aloce după dorinţă resursele şi să formuleze şi implementeze strategiile lor competitive (M. Porter 1980). În ţările foste socialiste resursele şi capabilităţile sunt menţinute şi dezvoltate diferit sub influenţa unor procese ca :

- liberalizarea masivă a activităţilor; - liberalizarea preţurilor; Astfel, China separă controlul managerial de

proprietate, pentru a promova agenţii economici autonomi şi concurenţa, dar nu şi privatizarea.

2. IMPLICAŢII PENTRU POLITICA

FIRMEI

Natura tehnologiilor complexe de produs diferă în mod radical de tehnologia produselor de masă. Procesul inovator în S.C.P. se pune în termeni de :

- accesibilitatea resurselor pentru firme; - capacitatea de inovare a firmei; - stimulentele şi oportunităţile de inovare;

Aceasta determină natura evolutivă a specificului competenţelor de dezvoltare a firmei. În Occident, se practică costurile scufundate (sunk costs), pentru clienţi şi interdependenţa între subsisteme, de unde, importanţa externalităţilor. Sprijinirea pe amplificarea legăturilor externe are o influenţă dominantă asupra strategiei şi structurii firmei. Firma nu se mai poate baza în continuare pe capabilităţile procesului intern de informare. Nici pe menţinerea avantajului competitiv prin economia de scară, deoarece presiunile pentru personalizarea produsului au înclinat balanţa de la scară spre domeniu. Pe aceste baze, reţelele de organizaţii sunt privite ca mijloace de amplificare a cadrului de timp pentru dezvoltarea noului produs şi dezvoltarea noilor pieţe.

3. PRODUSE ŞI PROCESE DE INOVARE

Vom aborda problema prin sublinierea

distincţiei dintre inovarea de produs şi cea de proces.Inovarea de produs, vizează introducerea de noi bunuri şi servicii într-o anumită piaţă.

Noile produse se bucură în general de publicitate.Inovarea de proces a fost de mare importanţă în ţările dezvoltate şi constituie sursa principală pentru o dezvoltare continuă şi rapidă a productivităţii în industrie.

În 2002, cercetătorii Edquist, Hommen şi Mc Kelvey, au arătat că, inovarea de produs este mai ales creatoare de locuri de muncă, iar inovarea de proces, reduce numărul de locuri de muncă.

Din analiză rezultă : inovarea de proces contribuie la creşterea standardului de viaţă, prin reducerea volumului de muncă cerută pentru un nivel dat de producţie şi permite surplusului de forţă de muncă să fie utilizat de către alte firme. Autorii justifică concluzia pe baza unui volum mare de studii empirice efectuat în ţări dezvoltate.

În România distincţia dintre inovarea de produs şi cea de proces este importantă din 3 motive.

1. Inovarea de produs, inclusiv introducerea de noi produse în portofoliul firmei sau pe o anumită piaţă, dar şi crearea de produse complet noi, par a produce atât creşterea producţiei cât şi cea a numărului locurilor de muncă.

2. Inovarea de proces (cea de tip tradiţional: reducerea costurilor prin economisirea forţei de muncă) permite rezolvarea problemei şomajului prin crearea de noi locuri de muncă în întreprinderi. În firmele cu surplus de forţă de muncă şi cost redus al forţei de muncă, procesul de inovare menit să reducă costul produsului nu reduce neapărat numărul de locuri de muncă. În această situaţie tehnologiile ce presupun muncă intensivă (consum mare de forţă de muncă) precum şi procesele, oferă mai ales o soluţie de reducere a costurilor de producţie, în raport cu tehnologiile care reduc necesarul de forţă de muncă pe baza intensităţii capitalului.

3. Multe tehnologii noi de proces în afară de reducerea costurilor oferă produse de calitate şi funcţionalitate superioară faţă de cele existente.

România are nevoie acută de tehnologii pentru a creşte calitatea şi funcţionalitatea produselor sale.

Nu este nici un dubiu că inovarea (aplicarea cunoaşterii şi a noilor idei la producţie, marketing, distribuţie) sunt esenţiale pentru România.


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Natura acestei inovări este decisivă. Aceasta trebuie să corespundă specificului României, cum ar fi descreşterea şomajului.

Aceasta înseamnă o creştere a orientării spre inovarea de produs: atât introducerea de noi produse în firmele industriale româneşti, cât şi crearea în România de noi produse din punct de vedere economiei la nivel global.

Procesul de inovare poate să se bazeze pe utilizarea eficientă a costului relativ redus al firmelor mici.

Îmbunătăţirea calităţii şi sporirea valorii producţiei este mai importantă decât minimizarea costului forţei de muncă. Subliniem că aplicarea în România a tehnologiilor bazate pe capital intensiv, şi a proceselor tehnologice menite să economisească forţa de muncă nu are încă o eficienţă ridicată. 4. BUNĂSTAREA COMUNITĂŢII

În economia de piaţă este important să nu uităm

scopul dezvoltării economice: bunăstarea, calitatea vieţii individului şi a comunităţii. Calitatea vieţii nu poate fi confundată cu nivelul P.N.B. Există mulţi factori în afara performanţei economice agregate care afectează bunăstarea.

Ocaziile de a accesa, crea şi aplica cunoaşterea, sunt inegal distribuite în societatea umană; ele generează o şi mai mare inegalitate în Economia Cunoaşterii (E.C.) la nivel global.

În consecinţă, o strategie de dezvoltare adecvată pentru E.C. în România va lua în consideraţie acest fapt, prin asigurarea distribuirii serviciilor necesare de bază, din punct de vedere uman: educaţie şi sănătate, pe cât posibil de echitabil. Utilizate adecvat noile tehnologii de informare şi comunicare pot sprijini echitatea.

Subliniem că: Economia Cunoaşterii nu este neapărat o caracteristică a economiei avansate şi nici doar cea mai recentă extindere a economiei industriale. E. C. este un nou stadiu de evoluţie a economiei globale cu implicaţii cuprinzătoare pentru fiecare, naţiune, firmă, regiune şi are un important impact social.

Economia Cunoaşterii impune modificarea strategiei de dezvoltare industrială. Noile realităţi ale E.C. impun decizii esenţiale privind adaptarea: - dezvoltarea tehnologică continuă a ţărilor avansate; - realizarea unor noi tehnologii specifice, necesare dezvoltării unor state mai puţin avansate, ca România, pentru a le face capabile să răspundă la provocările Economiei Globale a Cunoaşterii .

Kennth Arrow (laureat al premiului Nobel) sublinia (2001) două caracteristici ale noii cunoaşteri tehnologice.

- Noua cunoaştere tehnologică este costisitor de dezvoltat, dar odată dezvoltată, poate fi folosită în mod repetat, fără costuri suplimentare.

- Această caracteristică face cunoaşterea un cost fix şi o sursă de venituri crescătoare. Noua cunoaştere tehnologică este difuzată prin canale care nu pot fi privite ca fiind pieţe. Privite doar ca pieţe, ele nu sunt capabile să creeze sau să disimineze cunoaşterea în mod eficient, spre diverse segmente ale economiei.

Guvernele trebuie să joace un rol decisiv în

crearea şi diseminarea cunoaşterii ştiinţifice şi tehnologice, să promoveze spiritul organizaţiilor ale învăţării.

Carl Dahlman arăta că, răspândirea E.C. are ambele aspecte: oportunităţi şi ameninţări, pentru ţările în curs de dezvoltare:

- pe baza lucrărilor Băncii Mondiale asupra caracteristicilor E.C. şi implicaţiile politice asupra economiei naţionale

- măsurarea obiectivă a răspândirii activităţilor bazate pe cunoaştere în dezvoltarea ţării, pentru a putea fi comparate modul cum se plasează şi performenţa în raport cu alte tari.

5. ORGANIZAŢII ALE ÎNVĂŢĂRII

Transformarea întreprinderilor industriale româneşti din firme ale epocii industriale revolute, în companii care acţionează cu succes în Economia Cunoaşterii, în organizaţii ale învăţării, presupune modificarea treptată a climatului cotidian în raport cu învăţărea, a culturii de întreprindere. Principalele caracteristici pe care le constatăm la firmele preocupate de această problemă sunt.

Învăţarea este unul dintre puţinele avantaje competitive uşor accesibile pentru firmele româneşti. Aceasta presupune acţiunile mai jos menţionate.

1. Organizaţiile invăţării sprijină munca de echipă, delegarea largă de autoritate, responsabilitatea, creativitatea şi ameliorarea continuă a calităţii.

2. Învăţarea este integrată în desfăşurarea şedinţelor, acţiunea grupurilor de lucru şi în cadrul proceselor de muncă.

3. Sunt iniţiate acţiuni de învăţare încrucişate, între membrii echipelor de lucru. Persoanele care asimilează o gamă largă de principii şi deprinderi utile în procesul muncii sunt recompensate. Policalificarea şi pluricalificarea sunt apreciate şi deschid calea spre o promovare rapidă.

4. Învăţarea este integrată în toate activităţile personalului.

5. Este acceptată şi apreciată învăţarea de dragul învăţării.

6. Erorile sunt privite ca fiind ocazii pentru învăţare.


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7. Firma are încredere în alegerea cursurilor, a domeniilor pentru care salariaţii şi-au exprimat opţiunea. Salariaţii apreciază singuri necesităţile de învăţare.

8. Persoane cu diferite funcţii, din diverse departamente, învăţă împreună.

9. Sunt încurajate relaţiile de instruire colegială şi monitorizare a progreselor pentru a extinde şi accelera învăţarea.

10. Întreg personalul, indiferent de poziţia ierarhică are acces la învăţare.

Organizaţiile învăţării sunt acele unităţi în care

învăţarea constituie o prioritate. Învăţarea constituie în aceste unităţi atât un proces cât şi o sursă de valoare. În mod ideal fiecare individ din cadrul firmei este implicat în perfecţionarea sa prin procesul de învăţare.

Organizaţia, ca sistem, este implicată în continua îmbunăţăţire a tuturor activităţilor sale, a produselor şi serviciilor oferite, pe baza învăţării despre învăţare. Deoarece atât salariaţii cât şi întrega unitate se dezvoltă, personalul simte o permanentă reînoire a legăturii sale cu munca. Clienţii vor fi serviţi mai bine, iar întreprinderea îşi poate construi propriul său viitor.

În organizaţiile învăţării constatăm că: - învăţarea este abil integrată în activităţile

cotidiene; ea constituie o componentă firească a muncii şi nu o anexă;

- învăţarea constituie un proces continuu nu un eveniment aleatoriu;

- organizaţia învăţării este creativă: personalul transformă în permanenţă firma, îi accelerează evoluţia;

- organizaţia învaţă de la sine însăşi; - salariaţii învaţă organizaţia în privinţa creşterii

eficienţei, ameliorării permanente a calităţii şi inovării continue;

- întregul personal simte plăcere şi entuziasm deoarece face parte dintr-o organizaţie a învăţării.

CONCLUZII

Sursa de inovare provine tot mai ales de la firme mici de înaltă tehnologie, în vreme ce firmele mari asimilează rezultatele inovării tehnologice.

I.M.M. încep treptat să acţioneze ca specialişti orientaţi spre cercetare şi devin tot mai responsabile pentru promovarea cunoaşterii în domenii de vârf.

Colaborarea între firmele mici şi firmele mari este eficient pentru că ele au bunuri şi capabilităţi complementare.

Se constată că inovarea de produs este mai ales creatoare de locuri de muncă, iar inovarea de proces, reduce numărul de locuri de muncă. BIBLIOGRAFIE 1 Bragg, A., Bragg, M., ”Developing new business ideas”, Prentice Hall London, 2005. 2. Ciumara, M., “Investiţie şi corupţie în economia de tranziţie a României”, Al cincelea simpozion internaţional “Investiţiile şi relansarea economică.”Bucureşti, 2003 3. Cooper, L., ”Leadership and Management in the 21st Century”, Oxford University Press, 2005. 4. Curtin, T., Hyman, D., Husein, N., ”Managing a Crisis”, Polgrave Macmilton, London, 2005. 5. Popescu, R., Stoica, M.,“Provocări ale Managementului în secolul XXI”, Germania, Bochum, Proceedings, 2004.


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CLASICII REALIZĂRII EXCELENŢEI




REZUMAT. Comportamentul firmelor excelente, al firmelor care obţin realizări deosebite se remarcă prin acţiuni neconvenţionale (detaliile separă media de elită). Dintre acestea se remarcă: apropoierea de clienţi, implicarea specialiştilor de înaltă calificare, cultivarea entuziasmului pentru activităţile firmei, exigenţa în domeniul asigurării calităţii. ABSTRACT. The behaviour of excellent firms, companies able to obtain important achievements is characterised by inconventional activities (details separate the average firms of the excellent ones). Amoungh them we can observe: to meet the clients needs, involvement of highly qualified specialists, enthusiasms firms activities, high level quality assurance. CUVINTE CHEIE: firmă, excelenţă, specialişti, calitate KEYWORDS: firm, excellency, specialists, quality

1. INTRODUCERE

Tom Peters şi Robert Waterman arătau că, cele opt atribute ale excelenţei, aplicate de către companiile de succes, au efect deoarece au o bază teoretică verificată îndelung în practică. Acesta, deşi ignorată de majoritatea managerilor a trecut testul timpului şi aplicarea ei prezintă atractivitate pentru cei avizaţi.

Prin transpunerea în practică a celor opt principii s-au stimulat eforturi excepţionale din partea unor oameni absolut obişnuiţi şi aceasta cu regularitate. Companiile excelente au dus la apariţia unor campioni ai productivităţii, grupuri de indivizi care cred cu tărie în ideile lor, care înfrâng şi înlătură birocraţia şi-şi promovează proiectele în cadrul sistemului şi în afara acestuia, la clienţi. Aceşti campioni constituie o permanentă sursă de inovare; cunoaşterea şi iniţiativa sunt armele lor preferate.

Comportamentul campionilor, al celor ce obţin realizări deosebite se remarcă prin acţiuni cum ar fi:

- firma Hewlett Packard se mândreşte cu nivelul înalt al aproprierii de clienţi;

- ingineri - posesori ai M.B.A.- se implică în aspectele practice ale implementării noilor produse în fabricaţie;

- comportamentul lor este tot atât de entuziast ca al salariaţilor de la vânzare;

- pretutindeni în cadrul firmei domneşte un înalt standard de calitate al activităţii.

Excelenţa firmei e însoţită de o cultură organizaţională pe măsură.

Deşi multe dintre întreprinderile industriale excelente lucrează în domeniul producţiei de bunuri, ele se autointitulează ”Afaceri în domeniul serviciilor”.

Scopul lor este servirea clienţilor, aceştia domnesc în mod suveran. Clienţii nu sunt ”trataţi” cu tehnologii neverificate sau cu produse cu adaosuri inutile.

Clienţii primesc produse ce durează şi servicii livrate prompt. Calitatea înaltă şi serviciul prompt sunt în mod invariabil marcajul excelenţei.

Pentru a fi obţinute, este desigur necesară cooperarea tuturor, nu numai puterea şi efortul echipei manageriale de vârf. Companiile excelente necesită şi pretind şi obţin performanţe extraordinare de la oamenii obişnuiţi, medii.

Nu performerii de excepţie constituie cheia. Este solicitată atenţia, hotărârea fermă şi

stimularea continuă a omului obişnuit, denumită: ” productivitate prin oameni ”.

Aproape toate companiile o anunţă, dar puţine o realizează.

Nu este nevoie să apelăm numai la exemple din S.U.A., Japonia, Germania sau Marea Britanie. Firmele româneşti se afirmă nu doar în domeniul I.T. Am remarcat firme industriale româneşti care s-au înscris deja pe traiectoria excelenţei, cu toată


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turbulenţa mediului economic intern. Analiza recent efectuată la firma Hofigal din industria farmaceutică arată că această firmă dinamică şi inovativă se apropie mult de excelenţa durabilă.

Redăm mai jos atributele excelenţei în viziunea lui T. Peters şi R. Waterman. 2. CELE OPT ATRIBUTE ALE

EXCELENŢEI 1. Predispoziţia spre acţiune: preferinţa de a

face ceva, în loc să se vehiculeze o idee pe nesfârşite cicluri de analiză şi la comitetele de raportare.

2. A rămâne aproape de client: a afla preferinţele clienţilor şi a le satisface.

3. Autonomie şi antreprenoriat: a diviza corporaţia în firme mici şi a le încuraja să gândească independent şi competitiv.

4. Productivitate prin oameni: a crea în toţi salariaţii conştiinţa că eforturile lor sunt esenţiale şi că se vor bucura la rândul lor de răsplata succesului realizat de către firmă.

5. Firma să fie condusă de valori: a insista ca managerii să rămână preocupaţi de afacerile esenţiale ale firmei şi să promoveze o cultură puternică.

6. Menţinerea în cadrul afacerii de bază : a rămâne în cadrul afacerii pe care firma o cunoaşte mai bine (a decide care este specialitatea esenţială a companiei şi a lupta pentru dezvoltarea acesteia).

7. Organizare simplă, alocarea personalului strict necesar: a menţine un număr minim de niveluri ierarhice, cu puţini salariaţi la nivelurile superioare ; o singură dimensiune structurală trebuie să aibă prioritate (produsul, funcţiunea, zona geografică).

8. Păstrarea elasticităţii şi a fermităţii : a stimula un climat de înalt devotament faţă de valorile esenţiale ale campaniei, corelat cu preferinţele salariaţilor care acceptă valorile de bază (o combinaţie paradoxală a dirijării de la centru cu autonomia individuală).

Din toate cele opt atribute ale excelenţei apare în mod transparent legătura complexă şi strânsă, ce denotă în fapt armonizarea dintre strategia firmei şi cultura organizaţională a acesteia. În firmele excelente se poate remarca energia extraordinară, dincolo şi mai presus de datorie, pe care salariatul o depune pentru a influenţa destinul firmei şi propriul său destin.

Simpla cunoaştere a faptului că poţi să-ţi exerciţi controlul face diferenţa.

O altă trăsătură caracteristică a companiilor excelente este abilitatea de a conduce ambiguitatea şi paradoxul. Entuziasmul nu se poate contabiliza, nici inovarea, iraţionalitatea descoperirii, a produsului nou.

Instrumentele de analiză, cum ar fi costurile, nu sunt suficiente. Ceea ce economistul cu gândire

convenţională spune că nu este posibil, companiile excelente reuşesc în mod obişnuit.

De la focalizarea pe cost se trece la cea pe calitate. Flexibilitatea proiectului înlocuieşte regulile de comportament scrise cu contribuţia şi devotamentul fiecărei persoane.

Chiar şi managementul devine mai plăcut. În loc de jocuri cerebrale într-un turn de fildeş steril, se modelează valori prin antrenament şi exemplu pe teren, cu lucrătorul şi în folosul preţuitului produs-serviciu.

Se oferă o şansă speranţei, imaginaţia se înflăcărează, devine creatoare.

3. SCHIMBAREA SURSELOR

EXCELENŢEI.

Schimbarea domneşte pretutindeni; în prezent avem de fapt o accelerare a schimbării. Turbulenţa mediului modifică condiţiile în care acţionează companiile şi impune noi metode de management.

Multe dintre firmele excelente, odinioară exemple strălucite de reuşită, cum ar fi I.B.M. îşi pierd locul fruntaş, în vreme ce altele rămân în top.

În lucrarea ”Frontierele excelenţei” (1994) Robert Waterman lansează o nouă soluţie privind realizarea excelenţei: ”echipa auto condusă”. Mesajul, aflat chiar în subtitlul cărţii este că, trebuie să învăţăm de la firmele care dau prioritate utilizării potenţialului uman. Autorul ne sfătuieşte să învăţăm de la cei mai buni atâta vreme cât aceştia mai sunt în frunte şi continuă să progreseze. Chiar şi cei mai buni nu sunt totdeauna atât de buni pe cât par. Multe companii şi-au ascuns slăbiciunile în spatele dimensiunilor colosale.

În prezent scara de producţie nu mai poate oferi avantaj competitiv şi nici chiar simplă protecţie contra noilor competitori. Managerii ale căror minţi sunt rămase în status quo folosesc metode perimate şi transformă excelenţa în eşec.

Apar noi strategii, tehnologiile noi şi cunoaşterea devin accesibile; informaţia, viteza şi controlul oferă noi posibilităţi de succes.

Un nou tip de companii excelente se afirmă: ele sunt flexibile, rapide în reacţii, îndrăzneţe. Caracteristica lor este îmbunătăţirea şi schimbarea continuă.

Mai jos prezentăm noile idei privind excelenţa companiilor, aşa cum le sintetizează Robert Heller în lucrarea : ”În căutarea excelenţei europene” .

Acesta consideră că renaşterea firmelor europene este urmărită pe zece căi :

1. Transmiterea autorităţii (o delegare profundă a acesteia) fără însă a implica pierderea controlului sau a deciziei finale.

2. Transformarea culturii de întreprindere în secretul obţinerii succesului pe termen lung.

3. Demararea unor schimbări radicale, în întregul sistem al corporaţiei şi nu numai


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într-un compartiment care se manifestă deficitar.

4. Divizarea firmei in vederea obţinerii succesului, prin păstrarea sau câştigarea avantajelor ce caracterizează firmele de mici dimensiuni, in vreme ce compania, rămâne sau devine tot mai mare.

5. Exploararea potenţialului organizaţiei prin noi metode de abordare a conducerii centrale a companiei.

6. Menţinerea firmei in fruntea competiţiei, într-o lume în care vechile metode de a învinge au încetat să mai funcţioneze.

7. Realizarea unei reînnoiri constante, a feri succesul de contaminarea virusului decadenţei.

8. Conducerea celor ce motivează – a managerilor – astfel încât salariaţii să se motiveze ei înşişi.

9. A face echipele de lucru să acţioneze cu succes, devine o abilitate indispensabilă pentru atingerea excelenţei.

10. Realizarea managementului calităţii totale prin conducerea mai bună a tuturor activităţilor.

Din analiza mai atentă a lucrării lui Robert Heller rezultă că, firmele nu aplică o singură metodă în mod absolut. Intr-adevăr, confruntând valoroasele idei ale lui R. Heller cu o realitatea europeană în general, se constată că, managerii dau în mod frecvent dovadă de creativitate, acolo unde nu este neaparată nevoie sau este chiar indezirabilă. Lipsa unei autentice delegări, precum şi a obisnuiţei de a se concentra o perioadă mai îndelungată asupra unei singure activităţi - urmare a necesităţii de a rezolva problemele cele mai diverse în mod operativ - conduc pe manageri la realizarea unui mix de metode, nu totdeauna ales în mod fericit. Este adevarat ca aici există şi un aspect pozitiv, în cazul managerilor de elită. Aceştia reuşesc uneori, ca prin îmbinări inspirate, să creeze noi metode şi să adopte soluţii remarcabile pentru o anumită situaţie cu care se confruntă firma. Ne vom opri asupra aspectului legat de combinarea diverselor metode şi soluţii adoptate de firme în vederea potenţării efectelor pe care aceasta le aşteaptă, asupra surselor esenţiale de sinergie. Atunci când efectele sinergice sunt corect utilizate, beneficiile urmează în mod firesc, sub forma reducerii costurilor, a diminuării activitaţilor ce alminteri se efectuează în mod inutil, de mai multe ori în diferite sectoare ale companiei, a creşterii semnificative a loialităţiii clienţilor, a obţinerii unor preţuri mai mari, a realizării unor produse şi servicii cu caracter inovator, a sporirii remarcabile a numărului oportunităţilor de afaceri, a sporirii implicării personalului firmei.

CONCLUZII

Se poate remarca faptul că firmele nu aplică pentru a avea succes pe piaţă o singură metodă în mod absolut. Confruntând valoroasele idei ale lui R. Heller cu o realitatea europeană în general, se constată că, managerii dau în mod frecvent dovadă de creativitate. trebuie să învăţăm de la firmele care dau prioritate utilizării potenţialului uman. Promotorii excelenţei ne sfătuiesc să învăţăm de la cei mai buni atâta vreme cât aceştia mai sunt în frunte şi continuă să progreseze.

Companiile excelente au dus la apariţia unor campioni ai productivităţii, grupuri de indivizi care cred cu tărie în ideile lor, care înfrâng şi înlătură birocraţia şi-şi promovează proiectele în cadrul sistemului şi în afara acestuia, la clienţi. Aceşti campioni constituie o permanentă sursă de inovare; cunoaşterea şi iniţiativa sunt armele lor preferate.

BIBLIOGRAFIE

1. Ansoff, I., Mc Donnel, E., Implanting Strategic Management, Prentice Hall International, London, 1990.

2. Burduş, E.şi colectivul, Managementul schimbării organizaţionale, Editura economică, Bucureşti, 2000.

3. Dan, V., Isaic -Maniu, R., Muscalu, M.-S., Răgălie, Şt., Stan, E., Întreprinderea şi integrarea europeană, Editura Expert, Bucureşti, 2004.

4. Drucker, P. Managing for the Future, Butterworth Heinemann, Oxford,1994.

5. Heller, R., In Search of European Excellence, Harper Collins Publishers, London, 1998.

6. Nicolescu, O., Verboncu, I., Management, Editura Economică, Bucureşti, 1999. 7. Olaru, M., Managementul calităţii,

Editura Economică, Bucureşti, 1999. 8. Peters, T., Waterman, R., In Search of

Excellence, Harper Collins Publishers, New York, 1982.

9. Stoica, M., Doval, E., Popescu, R. , Ivănel, D., Jors, C. Evaluarea riscului financiar - bancar, Editura TIPART, Bucureşti, 2004, Tipart, Bucureşti, 2004.

11. Vasilescu, I. Românu, I. Dicţionar de investiţii, Editura Lumina Lex, Bucureşti, 2003.

10. Vasilescu, I. şi colectivul, Eficienţa şi evaluarea investiţiilor, Editura EfiCon, Press, Bucureşti, 2004.

12. Waterman, R., The Frontiers of Excellence, Nicholas Brealey Publishing, London, 1994.


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Quick Info Promoting entrepreneurs means creating jobs The European Enterprise Awards were launched three years ago to recognise and reward initiatives that support entrepreneurship at regional level. More than 350 national, regional and local authorities – including towns, cities and regions as well as public-private partnerships – competed in the 2008/2009 European Enterprise Awards. Participating countries – EU Member States and Norway – could select up to two candidates for the European competition. 13 were shortlisted for the awards in Prague. It is the Scarborough Renaissance Partnership, which has received the Grand Jury’s Prize for its pioneering enterprise and cultural renaissance work in the seaside town of Scarborough in north-east England. The project was selected for its impressive results in brining down seasonal unemployment. Five other initiatives from local authorities in Finland, Germany, Hungary, Spain and Sweden received award. The event was the final highlight of the First European SME Week, the European Commission's pan-European campaign to promote entrepreneurship in Europe and was organized in close cooperation with the Czech EU Presidency and the Committee of the Regions. Prizes were presented by European Commission Vice President Günter Verheugen, responsible for enterprise and industry, who said: “I am impressed how many initiatives have been created to make life easier for SMEs. Today's winner, the Scarborough Renaissance Partnership, demonstrates that promoting SMEs is in the benefit of our societies and can bring unemployment down. I invite all to share best practices. Our vision to be a world class space for SMEs can become true if we follow the examples of our today's winners.” Luc Van den Brande, President of the Committee of the Regions, said: "These awards are important, because they highlight the importance of local and regional authorities in encouraging entrepreneurship throughout the European Union. Through their local and regional policies, public authorities can help create the right conditions for entrepreneurship to flourish. I welcome the opportunity that these awards bring to acknowledge the key role that regions and cities play in creating jobs and developing growth."

The six 2009 European Enterprise Awards winners are: Grand Jury’s Prize Scarborough Renaissance Partnership (UK) has transformed a seasonal economy with unemployment in the winter 50% higher than in the summer into a more balanced year-round entrepreneurial climate offering increased employment prospects, particular through the development of a business park and state-of-the-art centre for creative and cultural industries. Entrepreneurship Promotion Instituto IDEAS (Spain) - a university-based enterprise-support programme has helped establish 400 innovative companies and enabled the creation of 4 000 jobs in the Valencia Region over the past 15 years. Red Tape Reduction ANTI-BUREAU (Hungary) – a company created by the Hungarian city of Miskolc to eliminate bureaucracy and cut costs in the management of local government services by combining and rationalising a wide range of services from heating, sewage and water, to refuse treatment, and even public transport and parking. Enterprise Support Gothia Science Park (Sweden) - an incubator, technology park and collaboration platform for IT companies with particular success in computer gaming development has created 50 businesses with 300 employees and helped in the diversification of a region previously heavily dependent on two large automotive engineering plants. Investment in Skills The Women's Enterprise Agency (Finland) – expert mentoring programme that encourages women to become entrepreneurs by one-to-one and group mentoring to new and growing SMEs. Responsible and Inclusive Entrepreneurship The Waldkirch Employment and Qualification Company -WABE (Germany) - a non-profit organisation involving a local network of citizens, private companies and government authorities that has helped 300 unemployed people with special placement problems find jobs in local businesses. Finally, the Jury's special mention goes to the project: "Our Power Spot," Bieliny, Poland - its unique tourism experience with field games using the region's folklore. The European Enterprise Awards were launched three years ago to recognise and reward initiatives that support entrepreneurship at regional level. (source: http://europa.eu/rapid/pressReleasesAction)


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EXCELENŢA ŞI DURABILITATEA INTREPRINDERILOR




REZUMAT. Evoluţia gândirii la nivel mondial în domeniul afacerilor, mai ales a gândirii strategice privind firma de afaceri, firma sau întreprinderea industrială, este un proces de sedimentare treptată a cunoştinţelor acumulate. Obiectivul principal al preocupărilor îl constituie ameliorarea situaţiei firmei, în momentul efectuării studiului şi în perspectivă atingerea excelenţei acesteia. ABSTRACT. The evolution of global thinking in business, especially strategic thinking on company business, company or industrial firms, is a gradual sedimentation process of accumulated knowledge. The main objective of the company's concern is improving the situation at the time of the analysis and achievement of excellence in the future. CUVINTE CHEIE: excelenţă, afacere, intreprindere industrială KEYWORDS: firm, excellency, business, industrial entreprise

1. INTRODUCERE Evoluţia preocupărilor în domeniul ameliorării activităţii firmei este jalonată de două curente principale de gândire . Cele două paradigme sunt :

A. Paradigma raţionalităţii strategice. B. Paradigma comportamentului

strategic. Interesul nostru se îndreaptă spre aceasta

din urmă, ai căror reprezentanţi (Lindblom, Peters, Waterman) îşi plasează eforturile într-un domeniu oarecum opus şcolilor de raţionalitate strategică. Deciziile strategice sunt situate într-un context strict pragmatic.

Obiectivul principal al preocupărilor îl constituie ameliorarea situaţiei firmei, în momentul efectuării studiului. Acţiunea se bazează pe motivarea personalului, o organizare simplă şi ascultarea atentă a clienţilor.

Tom Peters şi Robert Waterman, în lucrarea ”În căutarea excelenţei”(1982), un best seller al epocii, au răspândit –cu această ocazie- în mediul academic şi de afaceri, termenul de cultură de întreprindere sau cultură organizaţională, referitor la climatul uman din cadrul firmei.

Termenul de excelenţă, este de atunci

utilizat în mod frecvent pentru a caracteriza companiile de succes (companiile excelente, conform autorilor).

Aceştia susţin că, firmele excelente execută mai bine decât competitorii lor un număr de opt acţiuni importante.

Un deceniu şi jumătate mai târziu, în Europa, Robert Heller continuă, completează şi actualizează preocupările lui Peters şi Waterman.

În lucrarea ”În căutarea excelenţei europene” (1998), Heller analizează principalele zece strategii, aplicate de către firmele europene pentru a dobândi excelenţa.

În articolul alăturat prezentăm conceptele de bază ale lui T. Peters, R. Waterman şi R. Heller.

Considerăm ca fiind excelente firmele care, prin strategii adecvate, posedând un leadership (capacitate de a conduce) remarcabil, o cultură organizaţională şi o tradiţie de valoare, reuşesc să prospere în raport cu competitorii, înfruntând cu succes adversitatea mediului economic, prin valorificarea cu înaltă eficienţă a oportunităţilor acestuia.


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Putem privi deci excelenţa ca fiind combinaţia de succes dintre resurse, modalitatea organizării ( tehnice şi economice) şi eficienţa procesului managerial, în dinamica sa. Prin însăşi esenţa ei, excelenţa implică o combinare şi utilizare inspirată şi eficace a resurselor existente sau atrase ale firmei. Apare astfel ca imperios necesară analiza rolului sinergiei în atingerea excelenţei. Generarea sistematică şi menţinerea sinergiilor pozitive, pe termen lung, apar ca esenţă a dezvoltării durabile a firmelor excelente.

2. ORGANIZAŢII DURABILE

Considerăm trei piloni ai dezvoltării durabile, acceptaţi de către specialişti. -Dezvoltarea economică: generarea de bogăţie –

mai ales pentru cei săraci – în modalităţi compatibile cu ceilalţi doi piloni.

-Protecţia mediului ambiant: evitarea impactului negativ asupra sistemelor naturale şi sociale (poluarea, depopularea etc.). -Includerea socială: evitarea inegalităţilor prea mari de avere, sănătate, şanse de viaţă.

Faptul că şi afacerile pot fi durabile este controversat. În acelaşi timp este dificil să susţii şi să implementezi idealurile dezvoltării durabile dacă acestea nu pot fi aplicate şi lumii afacerilor, companiilor. Dificultăţile în aplicarea principiilor dezvoltării durabile la nivelul întreprinderilor industriale provin din următoarele considerente. A. Durabilitatea este o proprietate a sistemelor (de exemplu, economia) mai degrabă decât a componentelor, cum ar fi întreprinderile. Totuşi, majoritatea întreprinderilor industriale mari sunt sisteme complexe. B. Natura şi importanţa durabilităţii variază mult în funcţie de ramura industrială. Întreprinderile din industria chimică, metalurgică sau din unele sectoare ale industriei uşoare au asupra mediului un impact mai profund şi de durată mai mare în raport cu firmele din industria constructoare de maşini, electrotehnică sau electronică. Durabilitatea în domeniul serviciilor generale şi chiar şi a celor industriale este mai redusă în raport cu aceea a companiilor prelucrătoare. C. Durabilitatea însăşi este încă destul de controversată, atât datorită lipsei unor date statistice cât şi din cauza divergenţelor sociale şi culturale.

Astfel, responsabilitatea socială este cea rezultată din obiectivele stabilite de stakeholderi (deţinătorii de interese) şi de indicatorii de performanţă.

Obiectivele şi indicatorii sunt menite să asigure avantajul competitiv al firmei şi valorile pe termen lung ale acţionarilor (shareholderilor)

O altă problemă ce se poate ridica este aceea a tipului de durabilitate.

Susţinătorii tipului dur / tare al dezvoltării durabile tind să vadă protecţia mediului şi includerea socială ca fiind absolute şi nu doresc să facă nici un fel de compromisuri în favoarea dezvoltării economice. Partizanii dezvoltării durabile de tip slab / moderat, acceptă să negocieze pentru a facilita dezvoltarea economică.

Am ajuns în zona în care dezvoltarea durabilă ce vizează mediul ambiant şi cea privind durabilitatea dezvoltării afacerii, a întreprinderii, se despart. În cazul pe care-l studiem ne referim la prelungirea ciclului de viaţă al întreprinderii.

Vom reveni cu unele precizări în privinţa deciziei privind dimensiunea acceptabilă a impactului negativ asupra mediului natural sau social, în raport cu profitabilitatea. În cele ce urmează ne vom concentra asupra durabilităţii afacerii.

Scopul fundamental al afacerilor este de a obţine profit. Acesta poate fi realizat prin crearea de valoare pentru clienţi, corespunzător preferinţelor în schimbare ale acestora.

O afacere durabilă trebuie să îndeplinească condiţii de adaptabilitate şi flexibilitate. Crearea de valoare economică implică un beneficiu social prin realizarea unor acumulări de capital financiar care vor permite o viaţă mai confortabilă pentru noile generaţii şi creşterea numărului locurilor de muncă în prezent. Vom sublinia că, o afacere durabilă are şi alte obiective importante în afara profitului. Acestea rezultă chiar din esenţa dezvoltării durabile, ca principiu:

- protecţia mediului, care constă în menţinerea şi chiar extinderea valorilor capitalului natural;

- incluziunea socială, care constă în ameliorarea şi sporirea valorilor de capital social.

Deoarece dezvoltarea economică se bazează din ce în ce mai mult pe cunoaştere şi pe competenţele umane, putem adăuga un alt obiectiv al durabilităţii întreprinderii sau afacerii, acela de a mări valoarea capitalului uman prin educaţie, training şi prin alte mijloace. Creşte astfel rolul investiţiei în cunoaştere.

Strategia firmei de afaceri trebuie să se preocupe nu numai de obiectivele mai sus menţionate, oricât de importante ar fi acestea. Strategia trebuie să creeze o viziune împărtăşită,


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comună, referitoare la direcţia spre care întreprinderea se îndreaptă. Doar o strategie acceptată de către ansamblul personalului are şanse să fie implementată cu succes, să fie flexibilă şi durabilă.

Aceasta depinde de înţelegerea esenţei strategiei, de atractivitatea pe care aceasta o exercită asupra fiecărui salariat. Din acest motiv este de dorit ca strategia să fie realizată de jos în sus, să fie inspirată de realităţile fiecărui loc de muncă. În acest fel strategia firmei va avea vitalitate, va fi armonizată cu cultura organizaţiei.

Prin cultivarea perseverentă a relaţiilor generate de binomul strategie – cultură organizaţională se constituie şi menţine principala sursă de sinergii pozitive ce propulsează compania spre excelenţă şi-i asigură durabilitatea .

3. INTEGRAREA EXCELENŢEI CU

DURABILITATEA ÎN CAZUL ÎNTREPRINDERILOR INDUSTRIALE

Obţinerea unei viziuni împărtăşite în cadrul firmei permite crearea treptată a unei culturi organizaţionale suportive. Armonizarea dintre strategie şi cultura organizaţională constituie astfel esenţa şi garanţia excelenţei durabile. Se vor obţine în consecinţă, în mod cu mult mai facil :

- amplificarea performanţelor ce corespund nevoilor autentice ale întreprinderii, nevoi care nu se concentrează doar pe produs ;

- avantajul competitiv va rezulta din consideraţii ce vizează ansamblul ciclului de viaţă al produsului ;

- creşterea nivelului de comunicare în cadrul firmei, cu consecinţe asupra sporirii colaborării externe, obţinerea de informaţii suplimentare şi pertinente, posibilitatea de a influenţa pozitiv dezbaterile, de a identifica noi oportunităţi de afaceri;

- se va realiza înţelegerea faptului că, eco-eficienţa este mai ales un proces ce trebuie dezvoltat, decât un obiectiv ce trebuie atins momentan ;

- se va înfăptui integrarea durabilităţii (inclusiv a eco-eficienţei) în ansamblul afacerii, astfel încât să formeze o competenţă cheie, de bază, a acesteia.

Excelenţa va rezulta în mod firesc din sinergia elementelor enumerate mai sus, bazându-se în fiecare moment al evoluţiei sale pe acţiunea armonizată a binomului strategie-cultură organizaţională. Vom arăta acest fapt în cursul lucrării. Valorile promovate de manageri devin nefolositoare, fără forţă, dacă nu sunt acceptate şi trăite de către personalul organizaţiei. Faptul este cu atât mai adevărat pentru cazul managerilor de vârf care orientează eforturile unităţii. Aceştia influenţează situaţiile pe termen scurt şi lung prin tradiţia pe care o susţin şi consolidează, precum şi prin personalul pe care-l promovează treptat în echipa managerială. Pentru a asigura permanenţa armonizării strategie-cultură, echipa managerială motivează, şi impresionează salariaţii, orientându-i spre o viziune pozitivă, care ţinteşte valori importante şi duce la atingerea unor ţeluri dorite, râvnite. În acest fel este realizat un leadership autentic. Viziunea trebuie să fie prezentată într-un mod convingător, fascinant, captivant, irezistibil, astfel încât salariaţii să se simtă inspiraţi şi dornici să urmeze calea propusă. În Noua Economie bazată pe cunoaştere, productivitatea oamenilor şi a resurselor sporeşte şi-şi schimbă semnificaţia. În prezenta apar noi sisteme de măsurare care integrează mai bine excelenţa şi durabilitatea firmelor. Acestea se afirmă şi se impun treptat. În tabelul nr.1. prezentăm o comparaţie între vechile şi noile măsuri ale producţivităţii resurselor în cadrul firmelor industriale.

Tabelul nr.1. Schimbarea modului de măsurare a productivităţii resurselor

Măsuri vechi.

Măsuri noi.

Volumul total realizat. Intensitatea cunoştinţelor. Volumul de producţie realizat. Valoarea generată pe volumul de producţie realizat. Investiţia de capital Valoarea obţinută pe unitatea de capital investit. Cantitatea de material consumat pentru realizarea produsului.

Volumul de material folosit pentru a servi un client.

Energia şi materialul consumate. Energia şi materialul recuperate. Focalizarea pe produs. Focalizarea pe funcţiunea elementului. Eficacitatea pe termen scurt. Eficienţă pe termen lung.


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Schimbarea modului de a măsura rezultatele afectează treptat modul de a privi şi acţiona al celor implicaţi. Avem un proces de schimbare a motivaţiei. Companiile care se bucură de un nivel înalt de armonizare strategie-cultură au o flexibilitate sporită (care o amplifică chiar şi pe cea a proceselor tehnologice şi echipamentelor din halele de fabricaţie). Această flexibilitate permite adaptarea mai rapidă a firmei la cerinţele mediului economic. În perioadele de recesiune economică firma va supravieţui cu succes iar în momentul ivirii unor oportunităţi, unitatea va fi capabilă să le sesizeze şi să le valorifice, asigurându-şi o prosperitate durabilă. La un nivel înalt al armonizării dintre strategie şi cultura organizaţională, compania va putea să-şi construiască treptat căi proprii de ieşire din impas, chiar în lipsa unor oportunităţi momentane. Managerii adevăraţi, cei care fac lucrurile să se întâmple, integrează solidarităţile create din timp, cunoaşterea potenţialului personalului şi specificul proceselor pentru a reacţiona cu succes la provocările mediului şi a oferi excelenţă durabilă firmei pe care o conduc. Sinergiile ce rezultă din această armonizare se acumulează treptat şi propulsează firma spre culmile excelenţei durabile.

Leadershipul este cel care amorsează procesul iar ulterior, are un rol activ, de reglare şi menţinere a impulsului iniţial. Efortul pentru menţinerea excelenţei, pentru durabilitate, este asigurat de însăşi procesul de generare al sinergiilor rezultate din armonizarea strategie - cultură organizaţională.

CONCLUZII

Dezvoltarea economică se bazează din ce în ce mai mult pe cunoaştere şi pe competenţele umane. Un alt obiectiv al durabilităţii întreprinderii sau afacerii, acela de a mări valoarea capitalului uman prin educaţie, training şi prin alte mijloace. Creşte astfel rolul investiţiei în cunoaştere.

Strategia trebuie să creeze o viziune împărtăşită, comună, referitoare la direcţia spre care întreprinderea se îndreaptă. Doar o strategie acceptată de către ansamblul personalului are şanse să fie implementată cu succes, să fie flexibilă şi durabilă.

BIBLIOGRAFIE

1.Burduş, E.şi colectivul, Managementul schimbării organizaţionale, Editura economică, Bucureşti, 2000. 2.Heller, R., In Search of European Excellence,Harper Collins Publishers, London, 1998. 3. Nicolescu, O., Verboncu,I., Management, Editura Economică, Bucureşti, 1999. 4.Peters, T., Waterman, R., In Search of Excellence, Harper Collins Publishers, New York, 1982. 5.Stoica, M., Doval, E., Popescu, R. , Ivănel, D., Jors, C. Evaluarea riscului financiar- bancar, Editura TIPART, Bucureşti, 2004. Tipart, Bucureşti, 2004. 6.Vasilescu, I. Românu, I. Dicţionar de investiţii, Editura Lumina Lex, Bucureşti, 2003. 7.Vasilescu, I. şi colectivul, Eficienţa şi evaluarea investiţiilor, Editura EfiCon, Press, Bucureşti, 2004.


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