U.P.B. Sci. Bull., Series D, Vol. 69, No. 2, 2007 ISSN C o n t e n t s

Transcription

1 MECHANICS C o n t e n t s Xin-Jun Liu, Ştefan Staicu, Jinsong Wang Kinematics and kinetostatics analysis of the 3-DOF parallel cube-manipulator 3 HIDRAULICS Dan Robescu, Valentin Enciu Modelisation de l ecoulement de l eau dans une lance universelle à eau pulverisee - turap 19 AERONAUTICS Bogdan C. Teodorescu A crossfeed solution for the roll-coupling problem of high-performance airplanes 31 TRANSPORTS Traian Mazilu A dynamic model for the impact between the wheel flat and rail 45 AGRICULTURAL ENGINEERING Mahacine Amrani Apport du procede de lyophilisation sur la qualite des fraises marocaines 59 BUIDING MACHINE TECHNOLOGY Gabriel Iacobescu, Ionelia Voiculescu, Gheorghe Solomon A theoretical model for estimating the effects of the humidity in some electrode pastes on the diffusible hydrogen in the weld deposit 69 Dragoş Mihai, Eugen Străjescu From wavelength to R G B filter 77

2 Sorin Asproiu, Eugen Străjescu Thermal performance of hybrid injection moulds with molding zone made from non-metallic materials 85 MANAGEMENT Anca Alexandra Purcărea, Elena Fleacă Toward a system approach for power and influence in organization 93 Gheorghe Militaru, Sorin Ionescu Integrating business and society: the link between csr and competitive advantage 105

3 KINEMATICS AND KINETOSTATICS ANALYSIS OF THE 3- DOF PARALLEL CUBE-MANIPULATOR Xin-Jun LIU, Ştefan STAICU, Jinsong WANG Recursive matrix relations for kinematics and kinetostatics of a 3-DOF parallel Cube- manipulator having three prismatic actuators are established in this paper. The concurrent actuators are arranged according to the Cartesian coordinate system with fixed orientation, which means that the actuating directions are normal to each other. Three identical legs connecting to the moving platform are located on three planes being perpendicular to each other too. For such reason this type of mechanism is called Cube-manipulator. Knowing the translation motion of the platform, we develop first the inverse kinematics problem and determine the positions, velocities and accelerations of the manipulator. Further, the principle of virtual work is used in the kinetostatics analysis. Some matrix equations offer compact expressions and graphs for the forces of the three actuators Key-words: kinematics, kinetostatics, dynamics, parallel manipulator, virtual work MODELISATION DE L ECOULEMENT DE L EAU DANS UNE LANCE UNIVERSELLE À EAU PULVERISEE - TURAP Dan ROBESCU, Valentin ENCIU Les lances à eau pulvérisée sont de nouveaux matériels d intervention pour les sapeurs-pompiers roumains. Les paramètres (pressions, vitesses et énergie cinétique) caractérisant l écoulement de l eau sont difficilement mesurables du fait de la géométrie complexe de la lance. Ainsi, la simulation numérique de l écoulement de l eau dans les lances d incendie permet d obtenir les valeurs numériques de ces paramètres, de comprendre les phénomènes physiques de l écoulement et d affiner la géométrie hydrodynamique des lances.

4 The water mist discharge monitors are new entered accessories in firefighting equipment. The values parameters of flow (pressure, velocity and kinetics energy) are not known, because they are difficult to be measured by experiments, taking notice of the complexity of monitor geometry. By modeling the water s flux through monitors, you acquire numeric values of flow parameters and, also, the possibility to understand the phenomenon that take place inside the water monitor and the hydrodynamic improvement of their geometry. Mots cléf : modélisation, lance d incendie A CROSSFEED SOLUTION FOR THE ROLL-COUPLING PROBLEM OF HIGH-PERFORMANCE AIRPLANES Bogdan C. TEODORESCU The present paper deals with the problem of designing appropriate aileron-rudder interconnect ( crossfeed ) laws for improving the rolling characteristics of high-performance airplanes. As a result of analyzing the dependence of the pseudosteady rolling regimes on the airplane control variables, the author proposes a crossfeed law based on a new control correlation criterion, called the transcritical bifurcation criterion. The proposed solution allows both avoiding the occurrence of unwanted phenomena (unstable flight conditions, discontinuous airplane response to control inputs etc.), and increasing the maximum operational roll rate of a given airplane. The efficiency of the proposed crossfeed law has been verified by numerical case studies. Keywords: nonlinear flight dynamics, stability and control

5 A DYNAMIC MODEL FOR THE IMPACT BETWEEN THE WHEEL FLAT AND RAIL Traian MAZILU The flat is a serious fault of the rolling surface of the railway wheel. It appears when the wheel is blocked and slides on the rail during braking process due to the wear. The rolling of the wheel flat is dangerous due to the impact force, which applies stresses both to the track and the wheel and generates impact noise. This article presents the model for the analysis of wheel flat/rail interaction. The rail is considered as an infinite Euler beam supported on the continuous foundation with two elastically layers. The vehicle is reduced at a system of two elastic connected masses. The non-linear Hertzian wheel/rail contact is considered too. The solution of the motion equations are obtained by using an original Green s functions method. The influence of the flat geometry and rail pad stiffness for different cases of the vehicle traffic are presented. Keywords: wheel flat, vehicle, rail, Green functions APPORT DU PROCEDE DE LYOPHILISATION SUR LA QUALITE DES FRAISES MAROCAINES Mahacine AMRANI Ce travail expose l analyse et la modélisation de la cinétique de dessiccation des fraises entières et par tranches au cours du procédé de la lyophilisation. Un lyophilisateur Virtis 35L Gardiner a été utilisé. La lyophilisation a été réalisée à différentes températures de la plaque chauffante et pour différentes épaisseurs du produit. L'étude d impact des différents paramètres de lyophilisation des fraises, a démontré que la température a une incidence importante sur la réduction de la durée du procédé. Cela a pour effet d'abaisser le coût du procédé tout en préservant la qualité du fruit sec, ouvrant ainsi le

6 champ à l'application de cette technologie au traitement de denrées nouvelles. Mots clefs : modélisation, lyophilisation, fraises, Maroc, qualité. This work exposes the analysis and the modeling of the kinetics of desiccation of strawberries during the freeze-drying process. A lyophilisator Virtis 35L Gardiner was used. Freeze-drying was carried out at various temperatures. The impact study of the various parameters of freeze-drying process of Moroccan strawberries, showed that the temperature has an important incidence on the reduction process duration. thus minimizing the cost of the process while preserving the quality of the dry fruit and opening the field with the application of this technology to the treatment of new food products. Key words: modeling, freeze-drying, strawberries, Morocco, quality A THEORETICAL MODEL FOR ESTIMATING THE EFFECTS OF THE HUMIDITY IN SOME ELECTRODE PASTES ON THE DIFFUSIBLE HYDROGEN IN THE WELD DEPOSIT Gabriel IACOBESCU, Ionelia VOICULESCU, Gheorghe SOLOMON Taking into account the unfavourable effects the hydrogen has on the weld deposit it is of great importance that the diffusible hydrogen in the welded joint be controlled by checking the humidity in the electrode pastes. This action involves the determination of the effects the humidity in the electrode pastes has on the diffusible hydrogen in the welded joint by measuring the latter on an eprouvette loaded by welding with basic electrodes previously kept in the climate room that is with an already known humidity in the paste. This research study aims at establishing a theoretical model (a mathematical one) for the effects of the humidity in some basic electrode pastes on the diffusible hydrogen in the welded joint. Actually it is very difficult and no one has succeded do far to establish

7 the correlation (the total quantity of hydrogen present in the electrode paste mass) and the diffusible hydrogen in the weld deposit. Keywords: diffusible hydrogen, theoretical model, electrode, humidity. FROM WAVELENGTH TO R G B FILTER Dragoş MIHAI, Eugen STRĂJESCU This paper describes the implementation of an R G B filter based on the wavelength of illumination. For filter implementation have been used linear approximations for the CIE colour functions with a particular good approximation in the red domain. The algorithm is special for the good execution speed and the capacity to be implemented in virtual any system. Keywords: R G B, wavelength, filter, image processing, colour function INFLUENCE OF MOLD PROPERTIES ON THE QUALITY OF MOLDED PARTS Sorin ASPROIU, Eugen STRĂJESCU Around one third of all plastics materials are processed by injection molding, because it offer producing parts cheaper and quickly. Injection molding is a process that supposes applying heat to a plastic material to soften it and forces it to flow into a closed mold. Then, the material cools and solidifies, forming a specific product. The manufacturing of quality injection-molded parts depends on the part and mold design, process control, and material selection. The major issues in the development of injection molding tools include the progress in material technology and the developments in tool design methodology. It is essential to develop fast methods to manufacture tools for injection-molded-like prototype parts or mass-

8 produced parts. Due to these high requirements, it is more significant to use simulation methods to optimize the part before manufacturing. Keywords: Rapid prototyping; rapid tooling; rapid tool inserts; injection molding simulation. TOWARD A SYSTEM APPROACH FOR POWER AND INFLUENCE IN ORGANIZATION Anca Alexandra PURCĂREA, E. FLEACĂ This paper approaches the organizational science through a theoretical thinking in the field of power and influence within organization. The aim is to develop a model of power configuration within the organization, applying the system key concepts. The analysis has been taken into account the following aspects: reviewing the psychologists and sociologists researchers' efforts on power and influence phenomena, and the results of the authors previous empirical researches on quantifying the power factors within organizations. The main insight gained by the paper is that the managerial influence process model could be linked to the others organizational processes and integrated into a cohesive whole. Keywords: Organizational science, power bases, influence tactics INTEGRATING BUSINESS AND SOCIETY: THE LINK BETWEEN CSR AND COMPETITIVE ADVANTAGE Gheorghe MILITARU, Sorin IONESCU In this paper, we propose a new way to look at the relationship between business and society that does not treat corporate success and social welfare as a zero-sum game. Integrating business and

9 social needs take more than good intentions and strong leadership, it requires adjustments in organization. Companies must shift from a fragmented, defensive posture to an integrated, affirmative approach. Empirical data was collected from a cross-industry sample in Romania using a questionnaire form. It was shown that the corporations are not responsible for all the world s problems, nor do they have the resources to solve them all. Keywords: Corporate social responsibility, competitive advantage, social reputation, innovation