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Artykuły w czasopismach na temat "Systèmes multi-Contacts"
Couture, Jean-Simon. "Multiculturalisme". Anthropen, 2017. http://dx.doi.org/10.17184/eac.anthropen.047.
Pełny tekst źródłaRozprawy doktorskie na temat "Systèmes multi-Contacts"
Quetel, Eric. "Modélisation et simulation de contacts lubrifiés dans les systèmes multi-corps". Valenciennes, 2011. https://ged.uphf.fr/nuxeo/site/esupversions/84b3ed80-36b5-429f-a869-0d38f7165d4a.
Pełny tekst źródłaLifetime predictions and the improvement of the engine effectiveness represent nowadays parts of the most important commercial criteria in the automobile industry in order to response to the new environmental norms and to the constant growth of the market for low-cost components. In the different involved lubricated mecanisms, the ratio of the surface asperity heights to the lubricant film thickness has a decisive influence on the friction forces and thus on the energy dissipation and on the components wear. However, only a few simulation tools are nowadays available for the investigation of such tribological systems constraining the developers to often use their proper know-how or to conduct generally expensive measurements. In order to improve the dimensioning methods, three models are developed for the calculation of non-conforming elastohydrodynamic contacts, particularly for point and line contacts, and are applied to the simulation of cam-roller tappet contacts in high-pressure common-rail pumps and roller-raceway contacts in roller cell pumps. The first model is a one-dimensional representation of the elastohydrodynamic behaviour for heavily loaded contacts. It is based on the assumption that the contact pressure distribution may be approximated from the pressure distribution obtained in dry contacts and evaluate the central lubricant film thickness by means of dimensionless characteristic values. A simplified mixed lubrication model is additionally included. For the second and the third models, a more accurate solution method is adopted in order to consider locally the fluid-structure interaction. A discrete solution of the contact pressure and of the lubricant film thickness is obtained for point and line contacts using the multigrid technique. All three contact models are implemented as general force components or as contact elements in the multi-body system environment ADAMS/View from MSC. Software. Results from the discrete solver conform to those produced with the 1D model, especially for the central lubricant film thickness and confirm the assumption that the contact pressure distribution in heavily loaded elastohydrodynamic contacts approaches that in dry contacts. A robust coupling between the discrete solver for elastohydrodynamic point contacts and the multi-body system environment is achieved. However, instabilities are encountered by applying the solution algorithm to line contact problems due to incompatibilities with the multi-body system environment. Additional investigations are then required before employing the latter to industrial systems and the enhancement capability of the multi-body system environment to such complicated algorithms is questioned. Finally, successful applications of the unidimensional model in a high-pressure pump and in a roller cell pump are presented
El, Omari Hamid. "Amélioration des contacts ohmiques sérigraphies des cellules solaires en silicium multi cristallin". Lyon, INSA, 1994. http://www.theses.fr/1994ISAL0110.
Pełny tekst źródłaAs part of the renewable energies development, solar radiation quantum conversion has already reached industrial level. Present production permits to manufacture 0,1 x 0, 1 m2 solar cells at the rate of one per second. The aim of this work was to analyse and study screen printed contacts because of their importance in the component technology and to define a better industrial elaboration method. The analyse was made with the TLM method applied to multi-crystalline silicon. Contacts were studied according to various steps of the solar cells fabrication : influences of silicon dioxide layer (passivation layer) and titanium dioxide (anti reflection coating) were analysed. Thermal treatments steps (sintering and annealing) necessary for contacts realization, were studied in both cases : classical annealing and rapid thermal annealing. In the case of rapid thermal annealing, the influence of ambient gas and cooling speed were taken into account. The improvement is spectacular for the back contact treated at 850°C. In fact, the contact resistivity is divided by ten (compared with the standard processes) when there are a silicon dioxide layer and a titanium dioxide coating between the wafer and the contact. And this resistivity is divided by ten one more time if there is no silicon dioxide coating
Machado, Charles. "Modélisation et simulation électromécaniques par la MED des systèmes multi-contacts : application à la surveillance des roulements par une mesure électrique". Thesis, Amiens, 2015. http://www.theses.fr/2015AMIE0016/document.
Pełny tekst źródłaRecent studies have shown that an electric measurement made it possible to characterize the multi-contacts interfaces. The research initiated in granular media are transposed in a technological environment dedicated to monitoring and diagnosis of defects in bearings. This innovative method exploits the richness and sensitivity of a localized electrical measurement and correlated to the bearing load status. To demonstrate the potential of this method, experimentals electrical measurements are performed on a bench and signal analysis reveals similarities with traditional monitoring methods. From a numerical point of view, the bearing is modeled with the discrete element method (DEM), usually dedicated to the study of granular media, from which the mechanical behavior of the bearing dynamic is well reproduced. Electromechanical formulation is then introduced to derive a numerical electrical quantity of a bearing in operation, compared with the experiment. Typical electrical signatures in response to complex stresses (defects, clearance, imbalance, etc.) are studied. Studies of the mechanical behavior of rings opens interesting perspectives to understand and model their damage. While many studies have been conducted on the vibration monitoring of bearings, the use of a localized electrical method without sensor is still untapped and has promising results
Machado, Charles. "Modélisation et simulation électromécaniques par la MED des systèmes multi-contacts : application à la surveillance des roulements par une mesure électrique". Electronic Thesis or Diss., Amiens, 2015. http://www.theses.fr/2015AMIE0016.
Pełny tekst źródłaRecent studies have shown that an electric measurement made it possible to characterize the multi-contacts interfaces. The research initiated in granular media are transposed in a technological environment dedicated to monitoring and diagnosis of defects in bearings. This innovative method exploits the richness and sensitivity of a localized electrical measurement and correlated to the bearing load status. To demonstrate the potential of this method, experimentals electrical measurements are performed on a bench and signal analysis reveals similarities with traditional monitoring methods. From a numerical point of view, the bearing is modeled with the discrete element method (DEM), usually dedicated to the study of granular media, from which the mechanical behavior of the bearing dynamic is well reproduced. Electromechanical formulation is then introduced to derive a numerical electrical quantity of a bearing in operation, compared with the experiment. Typical electrical signatures in response to complex stresses (defects, clearance, imbalance, etc.) are studied. Studies of the mechanical behavior of rings opens interesting perspectives to understand and model their damage. While many studies have been conducted on the vibration monitoring of bearings, the use of a localized electrical method without sensor is still untapped and has promising results
Omar, Farah Samatar. "Modélisation multiphysique des roulements à billes par la Méthode des Éléments Discrets en régime Élasto-Hydro-Dynamique". Electronic Thesis or Diss., Amiens, 2022. http://www.theses.fr/2022AMIE0059.
Pełny tekst źródłaDuring this PhD thesis, we have focused on a digital tool for modeling ball bearing operating under elstohydrodynamic (EHD) regime. Based on an original description involving the discrete element method (DEM), the developed digital tool integrates all the components of ball bearings and enables realistic behavior under mechanical loading and kinematic conditions. Two models of ball bearings were considered and simulated with the digital tool, namely SKF 6208 radial contact ball bearing and SKF 7208 angular contact ball bearing. In order to check the standard indicators recommended by most ball bearing manufactures, a stiffness model for elliptical hertzian contact and an improved EHD formulation for lubricated contact are implemented in the discrete model of ball bearings. In addition, we have introduced into the discrete modeling an electrical capacitance model coupling rheological and dielectric properties of the lubricant with the Hertz's pressure at the contact between the ball and the raceways. The numerical predictions of lubricant film capacitance provided by numerical simulations are in good accordance, both qualitatively and quantitatively, with the experimental data available in the literature. The combination of the discrete modeling and the electrical approach enables efficient solutions to be provided in terms of lubrication regime in relation to the lubricant properties to optimize the bearing lifetime
Bruyère, Vincent. "Une modélisation multi-physique et multi-phasique du contact lubrifié". Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00782322.
Pełny tekst źródłaBruyère, Vincent. "Une modélisation multi-physique et multi-phasique du contact lubrifié". Electronic Thesis or Diss., Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0110.
Pełny tekst źródłaClassically, many assumptions are used to model the fluid behaviour in a lubricated contact : continuous film, constant viscosity across the film thickness, film thickness is very thin compared to other contact dimensions, Newtonian lubricant... However, some of them are not well-founded for the study of Elasto-HydroDynamic contacts with high sliding or to estimate the liquid distribution at the exit of the contact. An original numerical approach, based on the general fluid mechanics equations and taking into account the fluid/solid coupling and thermal effects, is developed here in order to give more physical insights to the usual modelling. First of all, the thermal effects are shown on the friction coefficient evolution for Thermo- EHD contacts. A minimum value is found concerning the friction value for the pure sliding case. It is explained by analyzing the heat transfer between the solids and the lubricant. The origin of the resulting local modifications of the film thickness and the existence of a film thickness for zero entrainment velocity cases are related to the presence of a high viscosity gradient through the film. A qualitative comparison is performed with experimental data from literature, validating the results. Second, the free surface flow of the lubricant around the contact is experimentally and numerically studied with a diffuse interface method. The capillary effects on the air/lubricant meniscus position are analyzed and quantitatively compared with experimental data from literature. Good agreements are found. An analytical approach is then developed, based on the numerical study of the two-phase flow. An analytical law predicting the liquid distribution is obtained. The exit area of EHD contacts is then investigated with a vaporous cavitation model highlighting the necessity of taking into account the effects of surrounding air and surface wettabillity. Finally, a first approach of the tri-dimensional two-phase flow is performed, showing the capillary effects on the interface location