Tesi sul tema "Résistance de frottement"
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Marchand, Anne-Sophie. "Etude de la résistance thermique de contact à l'interface de solides déformables en frottement". Lyon, INSA, 1998. http://theses.insa-lyon.fr/publication/1998ISAL0113/these.pdf.
Testo completoA numerical study is realised to estimate the Thermal Contact Resistance (TCR) between the tool and the workpiece during forming processes. The approach is based on a thermo-mechanical microscopic model of the contacting surfaces which assumes that during the relative motion between the tool and the workpiece, the perfectly rigid tool asperities create plastic waves on the workpiece contact surface. Empirical relationships are proposed, to determine the TCR as a function of the interface geometry and the thermal properties. The predictive capability of the relationships is obtained by comparing its outputs with the TCR determined from the numerical calculation. Furthermore, an experimental set up is designed so as to compare the experimental and the numerical values of the TCR and to validate the correlations for dry contacts. Another validation is also done by comparing the results with other thermal models for a particular geometry. These correlations are introduced in the numerical code of hot forming processes
Aliouche, Djamel. "Contribution à l'étude des mécanismes de frottement des étoffes". Mulhouse, 1991. http://www.theses.fr/1991MULH0189.
Testo completoBollo-Kamara, Nicholas Odunola. "Étude de la mobilisation du frottement d'un géotextile sollicite en traction dans un milieu analogique bidimensionnel". Lyon, INSA, 1992. http://www.theses.fr/1992ISAL0071.
Testo completoThis thesis contributes to the understanding of the mechanism (friction) governing the behaviour of fabrics (geotextiles) subjected to tensile forces. A review of existing literature on friction mobilisation at soil-geotextile interface as well as test methods (shear and pull out or extraction) with respect to the latter are presented. A theoretical analysis of the behaviour of geotextiles under extraction in non cohesive soils is arso resented. The resulting constitutive relationships provide the basis for the exploitation of the pull out tests carried out to determine the interface law parameters. The experimental study includes pull out tests in a bidimensional analogue model (SCHNEEBELI's cylindrical steel rollers), and friction tests using shear equipement for an eventual comparison with the extraction test results
Ben, Abdallah Adel. "Influence de la microstructure et des propriétés des matériaux céramiques sur leur résistance à l'usure et leur comportement en frottement". Ecully, Ecole centrale de Lyon, 1990. http://www.theses.fr/1999ECDLA021.
Testo completoBenkhalifa, Mohamed Tai͏̈eb. "Ecoulement visqueux de diffusion binaire dans un pore : application à la détermination du coefficient de diffusion équivalent dans un milieu poreux". Poitiers, 1994. http://www.theses.fr/1994POIT2327.
Testo completoChampagne, Karine. "Contribution à l'étude des paramètres de résistance au cisaillement des barrages en béton du Québec". Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/5512.
Testo completoDetourbe, Sylvie. "Contribution à l'étude des traitements mixtes de nitruration et d'oxydation assistés par plasma en vue d'améliorer la résistance à la corrosion atmosphèrique des aciers". Vandoeuvre-les-Nancy, INPL, 1989. http://www.theses.fr/1989NAN10399.
Testo completoLe, Thiet Trung. "Etude du processus de vibrofonçage d'inclusions cylindriques en chambre d'étalonnage : application aux pieux". Marne-la-vallée, ENPC, 2005. https://pastel.archives-ouvertes.fr/pastel-00001557.
Testo completoMeheux, Mathilde Odile Anne. "Influence des additifs de lubrification sur la formation de tribofilms, le coefficient de frottement et la durée de vie en fatigue des roulements". Ecully, Ecole centrale de Lyon, 2009. http://www.theses.fr/2009ECDL0001.
Testo completoGears, rolling bearings and synchronizers are lubricated with a single oil, selected according to gear specifications in manual transmissions. Lubricant related Rolling Contact Fatigue (RCF) damage has been reported in bearings. Several explanations can be considered, but this work focuses on the effect of lubricant additives. As explained in the literature, the lubricant (base oil and additives) can react at the surface of the test pieces and/or on the fatigue crack faces open to the oil. Some effects like hydrogen embrittlement are known, but it has not been clearly established yet whether the presence of tribofilms and the adsorption of additives contribute to the initiation and/or propagation of fatigue cracks. The influence of lubricant formulation on fatigue life has been evaluated using accelerated fatigue tests (on a twin disc machine) performed under pure rolling and sliding conditions. Under pure rolling, the detergent containing oil generates a reduction of fatigue life compared with the other oils tested. The tribofilm formed at the surface of the discs was studied using surface analysis techniques (EDX, AES). It shows similarity in terms of elemental composition and thickness with model tribofilms generated in a ball on disc tribometer (Mini Traction Machine). The latter was used to evaluate the influence of lubricant formulation on tribofilm formation. The detergent seems to be a key additive generating a thick surface tribofilm. Finally, the chemical content of a crack was analysed. A FIB cross section allowed EDX analysis of the faces. Additive elements were found. Fatigue life did not vary much between the formulations tested under sliding conditions, but the presence of additives in the crack allows the following hypothesis : the chemical content of a lubricant can influence crack propagation
Tcheukam, Toko Denis. "Étude de la couche limite générée par l'action de la houle et/ou du courant sur fond hydrauliquement lisse : application au transport sédimentaire". Le Havre, 1997. http://www.theses.fr/1997LEHA0001.
Testo completoGerthoffert, Jonathan. "Prévision des performances de freinage des avions sur les pistes contaminées à partir des mesures de frottement". Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0018.
Testo completoAircraft braking performances depends strongly on runway surface conditions. Water on runway can severely degrade these performances. Airport operators have to inform aircraft crews about runway surface conditions to allow pilots performing landing distance calculations. Friction measuring devices are a widely used tool to characterize runway surface conditions. However, friction results are highly scale-dependent (in terms of mass, speed, tire dimension and pressure…), which are significantly different between ground friction device and aircraft. Ground friction measurements are therefore not representative of aircraft braking performances. The methodology developed in this thesis consists in the construction of a transfer function between the friction measuring device and the aircraft from a modeling of force within the tire/runway contact area. A physical model, the so-called Brush model, has been adapted to wet and flooded runways. A specific model has been developed to describe water effect ontire/runway contact area and force distribution within this contact area. The applicability of this model to a ground friction measuring device and one aircraft has been experimentally validated. Finally, the complete methodology has been validated using experimental data from the Joint Winter Runway Friction Measurement Program (JWRFMP) and data obtained in this thesis
Abderrahim, Abdelkrim. "Utilisation d'un mini-pressiomètre pour la mesure directe du frotttement [i. E. Frottement] à l'interface sol pulvérulent-inclusion". Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPL058N.
Testo completoSouza, Eduardo de Cursi. "Amarrage par des fils sans raideur à comportement unilatéral". Montpellier 2, 1991. http://www.theses.fr/1991MON20054.
Testo completoLe, Thiet Trung. "Étude du processus de vibrofonçage d'inclusions cylindriques en chambre d'étalonnage. Application au pieux". Phd thesis, Ecole des Ponts ParisTech, 2005. http://pastel.archives-ouvertes.fr/pastel-00001557.
Testo completoZhao, Fei. "Study on mechanical properties of the in situ TiB/TiC reinforced titanium matrix composites". Troyes, 2010. http://www.theses.fr/2010TROY0030.
Testo completoThe aim of this research is to study the effects of reinforcements TiB and TiC materials by experimental analyzing structures and mechanical testing of properties of in situ synthesize TiB/TiC reinforced titanium matrix composites. The tensile, friction and fatigue properties of in situ TiB/TiC reinforced composites structures were tested. Finite element analysis was also used to simulate the effect of the reinforcements. The results show that the reinforcements can play an important role in the composites properties. The elastic modulus and shear modulus have some relation with the type, the quantity, the shape and the distribution of the reinforcements in the composite materials. Some formulas about the modulus of the composites are suggested by modelling the composite behaviours with numerical method. The reinforcements can prevent the crack initiation and propagation in static load. For the fatigue properties, the reinforcement TiB reduces the fatigue life of the composites under high level of load, but increases it in low load conditions, while TiC reinforcements can improve the fatigue strength of the composites. So in practice, the applying conditions of the composites should be considered. The contents of the reinforcements should be determined by taking account of the manufacturing costs, so that we can to optimize the practical needs and to but reduce the costs
Sahyoun, Abdallah. "Étude numérique de la formation des assemblages par clinchage et de leur résistance mécanique". Compiègne, 2012. http://www.theses.fr/2012COMP2013.
Testo completoLepré, Nathalie. "Synthèse et élaboration d'un matériau composite pour garnitures de freins : caractérisations physico-chimique et mécanique du materiau". Le Havre, 1997. http://www.theses.fr/1997LEHA0005.
Testo completoPeronne, Simon. "Modélisation expérimentale et analyse spatio-temporelle de l'hydrodynamique de la zone de déferlement à la zone de swash". Caen, 2010. http://www.theses.fr/2010CAEN2064.
Testo completoA study on the dynamics of the free surface and flow from the surf zone to the swash zone is proposed, based on results obtained from an experimental model in wave flumes, monitoring Lagrangian of the free surface and Eulerian measurements of the internal flow. After an inventory of results related to this area, a first part is devoted to the description of measuring systems, validation of measurement tools in this area and the presentation of the possible swells scenarios. Secondly, the use of algebraic and analytic tools in data processing is described and justified. A method for extracting the bore velocity from the surf zone from video measurements is also presented. The analytical work is divided into four stages. An analysis of the characteristics of the bore in the surf zone is proposed based on the video measurements. Then, the generation and eventual release of secondary waves (high or low frequencies) from non-linear processes, through different approaches classical and original, is treated. A comparison between the secondary wave generation and the dissipation of the potential energy is proposed and a study on wave pairing is also written. Thus, the internal flow in the transition zone between the inner surf zone and swash zone is studied to describe the interactions between offshore currents generated during the backwash phase and incident bore. Finally, after an analysis of boundary conditions in the inner surf zone, the last part is devoted to the study of the flow in the swash zone and the related bottom shear stress and friction factor
Toutiri, Corneille. "Modélisation dynamique et thermique d'une fibre de verre en cours d'étirage". Poitiers, 1999. http://www.theses.fr/1999POIT2261.
Testo completoPennec, Fabienne. "Modélisation du contact métal-métal : application aux microcommutateurs MEMS RF". Toulouse 3, 2009. http://thesesups.ups-tlse.fr/611/.
Testo completoThe insertion of RF MEMS micro-switches into real architecture necessitates reduced actuation voltage and dimensions that gives more importance to surface effects. Therefore most of the limitations are related to the quality of the contact and the reliability. In this context, a tool for calculating the electrical contact resistance of DC contact micro-switches has been developed. The tool will be very efficient for investigating the impact of materials, roughness and topology on the quality and the contact performances. Firstly an overview of the different available methods (analytical, numerical, experimental) to analyze the mechanical and electrical contact of rough surfaces has been performed. Then we have designed and fabricated two architectures of test structures, one with mechanical actuation and the other with electrostatic actuation in order to validate the contact modeling methodology that we implement. The originality of this work relies on a novel approach by using a reverse engineering method to generate the real shape of the surface. The mechanical contact analysis is then performed through finite element multi-physic simulation using ANSYS 11 platform. The mechanical analysis is completed with an electrical analysis, using analytical formulations derived from electrical contact theories and referring to the previous mechanical results. .
Van, Ruymbeke Bruno. "Etude expérimentale des régimes de coexistence toroïdal/spiral en écoulement de Taylor Couette diphasique avec injection de bulles Quantitative visualization of swirl and cloud bubbles in Taylor–Couette flow, in Journal of Visualization 20, 2017". Thesis, Brest, 2018. http://www.theses.fr/2018BRES0059.
Testo completoThis experimental study deals with wall friction reduction by injection of millimetric bubbles. This work is in the continuity of Mehel (2006) and Fokoua (2013) PHDs. We focus on the friction modulation, Taylor's cells characteristics and the gas phase structure, for coexistence regimes (alternance between toroidal-spiral patterns). The gap geometry is characterized by the ratio of radii (0,9). The Reynolds and the air volumetric fraction are varied in the ranges [1700-50000] and [0-0,1%] respectively. By high-frequency visualizations and defect (dislocations and cell fusions) analysis method, we characterized the transition between the regimes of structured coexistence, unstructured coexistence and developed chaos. By Stereo-PIV (2D3C) measurements, we characterized the liquid phase in a meridian plane and discriminated the contributions of random and coherent motions to the turbulence. Simultaneous measurements of the torque exerted on the inner cylinder evidence different mechanisms influencing the wall friction: turbulent shear either due to the bubbles wake or to the jets between cells and relaxation of the azimuthal velocity gradient. The analysis according to the patterns and regimes shows that the maximum torque is reached for the toroidal pattern and structured regime. The high frequency images of the bubbles were analyzed by discriminating their radial position in the gap. Self-similar laws with respect to the rotational Froude numbers either characterizing the cells or the inner cylinder are obtained for both void fraction and axial velocity of the gas phase. The air volumetric fraction controls the rising velocity of the cells, the azimuthal velocity of the gas and the frequency of the azimuthal wave
Talantikite, Malika. "Etude structurale, rhéologique et électrochimique de fluides complexes réducteurs potentiels de traînée". Thesis, Le Mans, 2017. http://www.theses.fr/2017LEMA1012/document.
Testo completoIn terms of energy saving, drag reduction hasan undeniable interest. In some cases drag reduction with additives can reach 80% compared to pure solvent. This phenomenon has applications in many fields suchas transportation of hydrocarbons and cooling and heating systems. Three systems which have the capacity to selforganizein aqueous or organic media have been studied in order to check their possible ability to reduce hydrodynamic friction.We worked on a polysoap (80C12) based on polystyrene skeleton to which tertiary amines bearing alkyls chains of 12 carbons. This compound formsmicelles in water whose cylindrical shape has been demonstrated by light scattering and Cryo-TEM. The studies of the mass transfer on a rotating disk electrode and the rheological results have showed for the 80C12solutions several characteristics attributed to the dragreducing additives.Rheological studies on the systems lecithin/decane and ionomers/toluene, highlight the viscoelastic properties of the anisotropic associations of these compounds
Courbon, Cédric. "Vers une modélisation physique de la coupe des aciers spéciaux : intégration du comportement métallurgique et des phénomènes tribologiques et thermiques aux interfaces". Phd thesis, Ecole Centrale de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00713527.
Testo completoKouakou, N'guessan Moïse. "Comportement mécanique des sols grossiers hétérogènes à matrice". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0043.
Testo completoCoarse-grained soils, which are materials containing grains ranging from micrometers to several tens of centimeters, are frequently used in various geotechnical projects such as dikes and embankments. The determination of their shear strength in standard laboratory devices is difficult because of the presence of large grains. Different approaches (scalping, substitution, and parallel gradation) could be used to reduce the grain size of the tested sample. However, these techniques involve a change in the percentage of each fraction in comparison to the initial sample. Therefore, it is important to know how the shear strength is altered by the variation in the grain size distribution curve. The aim of this study was to establish a methodology for estimating the shear strength of coarse-grained soils with matrix by testing their fraction compatible with the available shear device size. The parallel gradation method was used and the influence of the fines content increase in the reconstituted soil was investigated. Two soils with different fines content were studied: a limestone aggregate with 1.9% fines and a natural gravel with 15% fines. The shear strengths of parallel graded samples of these soils at the same dry density under saturated and unsaturated conditions were determined in devices with different sizes. The results showed, for the soil with fines content lower than 4%, a suitable estimation of the initial soil shear strength for a low grain breakage ratio. This low grain breakage ratio is ensured for low normal stresses, under 100 kPa in the case of the studied aggregate. For the soil with higher fines content, it has been shown that the initial soil friction angle is correctly estimated when the reconstituted soil has the same grain arrangement as the initial soil, i.e., for a fines content lower than 30%. However, the difference in fines content between the initial and reconstituted soils led to an overestimation of the initial soil cohesion. A cohesion – fines content relationship was proposed to predict the cohesion of the initial coarse-grained soil. Furthermore, when the fines content in the reconstituted soil is higher than 30%, it was shown that the scalping method provides a suitable estimation of the initial soil shear strength when the density and percentage of scalped grains criteria are fulfilled. Recommendations were made to determine the shear strength of coarse-grained soils with matrix based on their characteristics and the size of the available device
Nguyen, Thi Thu Tra. "Dynamic instabilities of model granular materials". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSET007/document.
Testo completoThis thesis reports a laboratory study on the dynamic instabilities of model saturated granular material using a triaxial apparatus. The term instability consists of isotropic collapse and liquefaction under isotropic compression and of stick-slip under triaxial compression in drained condition. The instabilities spontaneously occur at unpredictable effective stress with unexpected buildup of excess pore pressure irrespective of fully drained condition, contrasting with the instability-free behaviour of natural granular materials. In isotropic compression, instantaneous local collapse happens and in triaxial compression, very large and quasi-periodic stick-slip occurs with sudden volumetric compaction and axial contraction. Sometimes, these local failures (collapse and stick-slip) can develop into total liquefaction failure, destroying completely the granular structure. High time-resolved data permit the discovery of a new family of dynamic and static liquefaction. Passive acoustic measurements allow the identification of typical spectral signature. For stick-slip phenomenon, the slip phase with constant duration of stress drop can be interpreted as dynamic consolidation at constant deviatoric stress, limited by a unique boundary inside the critical state line in the effective stress plane. The precise temporal sequence of mechanical measurements excludes the generated pore pressure as the main cause of the instabilities. However, the role of pore pressure is emphasised by consistent quantitative relations between the amplitude of incremental stresses, incremental strains and the ephemeral stabilised excess pore pressure developed during the dynamic event, leading to the quasi-deterministic nature of granular instabilities. These empirical relations are based only on the short-lived maximum vertical acceleration and governed separately by the confining pressure and the initial void ratio. The similarity of pore pressure evolution for different kinds of instability strongly suggests some common speculative triggering mechanisms, probably originated from different rearrangements of the granular micro-structure
Laporte, Julie. "Etude et modélisation de l'endurance électrique de micro-contacts soumis à des sollicitations de fretting-usure : caractérisation de nouveaux dépôts base Argent". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC034/document.
Testo completoAdvanced instrumentation in mechanical systems (aeronautical, automobile etc…) goes hand in hand with an ever increased use of electrical connectors. However, the unfavorable operating environment (chemical attack and vibrational loads) causes more or less severe degradation of electrical contacts, which in turn perturbs their electrical conductivity. Gold plating is usually applied in electrical contacts in order to limit damage and to ensure connector stability. However, economic constraints and the high cost of gold require cheaper alternatives. Amongst conductive metals, silver is the best candidate. Hence, the purpose of this PhD project is to investigate the electrical response and the degradation of silver coatings when subjected to fretting loadings. The study is divided into three main research axes. The first axis consists in realizing a complete study of a homogeneous silver/silver contact in order to identify the degradation mechanisms that are responsible for the electrical failure, both in fretting loadings and reciprocating sliding. It was possible to formalize a predictive model, using an energy density approach, allowing to extrapolate the lifetime of the contact as a function of various loading parameters. A complementary study also showed the impact of a corrosive sulfur atmosphere on these electric contacts. As part of the second research axis, an investigation of the tribological and electrical behavior of novel silver-based materials, solely synthesized as a gold replacement, was performed. The analysis of these homogeneous contacts allowed to explain the degradation mechanism and the mechanical behavior of these contacts when subjected to a wet environment. In the last research axis a study was led on the same silver-based materials but in a heterogenous configuration against a gold coating in order to identify the tribological and electrical behavior of these contacts when composed by materials with similar or opposite properties
Francis, Roméo. "Etude du comportement mécanique de micropieux modèles en chambre d'étalonnage. Application aux effets de groupe". Phd thesis, Ecole Nationale des Ponts et Chaussées, 1997. http://tel.archives-ouvertes.fr/tel-00523154.
Testo completoHannel, Sophie. "Sur l'importance de la transition de glissement en fretting pour la connectique". Ecully, Ecole centrale de Lyon, 2000. http://www.theses.fr/2000ECDL0027.
Testo completoOn all mobile electronic devices, vibrations lead to fretting stresses on electrical connectors contacts. Resulting contact damages hinder the current flow. The main result of this research is the correlation between the electrical behaviour and the fretting sliding condition : for oxygen sensitive materials such as bronze or tin, a partial slip condition guarantees a low and stable electrical resistance, whereas a gross slip condition leads to an irreversible increase and a strong instability of contact résistance. For oxygen insensitive materials such as gold or silver, the electrical behaviour is conditioned by substrate exposure which sooner or later occurs in gross slip. The technological interest lies in the demonstration of a threshold in relative displacement for a satisfactory electrical behaviour. In order to calculate this threshold and thus anticipate the contacts electrical behaviour, a mechanical analysis using 2D finite element modelling of the elastic plastic contact is applied to the experimental bronze/bronze contact. The experimental determination of a relevant friction coefficient, essential input parameter for the efficiency of the model, required an analysis the results of which might be extended to any contact situation involving intense adhesion and plastic deformation. The analysis consists in separating the friction coefficient from obstacle effects and plastic shearing of the interface. Thanks to this analysis, the calculated relative displacement at transition corresponds to that measured in experiments. This experimental validation of the model opens the way to a predictive analysis of the connectors electrical behaviour
Ihsan, Mohammad. "Analysis of the stability of slopes submitted to water infiltration using advanced models : coupled hydromechanical model and Nonlinear Dynamics Method". Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10091/document.
Testo completoThis research concerns analysis of landslides, which constitute a major natural risk responsible for high human losses as well as large damages to structures, infrastructure and natural environment. This issue becomes particularly important, because of the climate change, which increases the risk of heavy rains as well as severe drought and consequently the risk of slope instability due to the environment change. Generally, analysis of slope stability is conducted using the limit equilibrium theory. As this theory does not take into consideration the process of mobilization of the friction, it could lead to an overestimation of the safety factor. A reliable analysis of the slope stability, in particular in heterogeneous soils submitted to the water action, requires the use of advanced numerical methods. Two methods were used in this research: the coupled hydro-mechanical method and the nonlinear dynamic method
Ripard, Valentin. "Tribological characterization of greased drive-shaft : Evaluation of constant velocity joint durability". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI083.
Testo completoNew customer desires are leading car manufacturers to new challenges. Indeed, enhanced vehicles like SUV (Sport Utility Vehicle) becomes more and more popular, especially in Europe. These vehicles involve some modification over the usual mechanical transmissions designs. This vehicle type has a higher angularity than sedans for example. This desire modification has 2 impacts: the increase of slipping in the transmission and its influence on the durability of the components. The angularity modification remains one of the major lines of research in recent years for car manufacturers. Its increasing influences efficiency. Indeed, this axis of improvement is attractive for manufacturers due to new environmental standards but also an increase in oil price. In addition, a car must have a reliable transmission that does not require, in the case of constant velocity joints, any maintenance during vehicle life. The following work will focus on this objective. The main goal of this manuscript is to understand the wear mechanism of the tripod constant velocity joint (CVJ). An analysis of the kinematics was first conducted to reproduce contacts on test rigs. It relied on data from the bibliography but also a simulation of solid dynamics. In addition, the design of a new observation rig using additive manufacturing made it possible to experimentally reproduce slipping in tripod. Furthermore, a characterization of greases used in Groupe PSA transmissions was performed in order to know the friction coefficients inducing the shudder level of the CVJ. These are also essential in order to judge the efficiency of the component. Finally, a wear investigation is performed to explain the possible lubrication failure mechanisms with greases proposing different mechanical behaviour. This approaches enables the transmission designer to choose a grease ensuring maximum durability of transmission components. Looking ahead, a lubricant characterization rig specially designed for tripod joint contacts has been designed. It will thus allow a more complete characterization of further lubricants to this essential vehicle component
Du, Peng. "Numerical modeling and prediction of ship maneuvering and hydrodynamics during inland waterway transport". Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2459.
Testo completoIn this thesis, the ship hydrodynamics during inland waterway transport and ship maneuvering are investigated using CFD (Computational Fluid Dynamics) based onOpenFoam. Validation and verification studies are carried out for the mesh convergence, time step convergence, sensitivity to turbulence models and dynamic mesh techniques. A quaternion-based 6DoF motion solver is implemented for the trim and sinkage predictions. Environmental effects on several inland vessels (convoy 1, convoy 2, tanker) are studied using the validated numerical models. Three important aspects, the confinement effect of the waterway, head-on encounter and ship-bridge pile interaction are simulated. The testing conditions cover a wide range, including various channel dimensions, water depths, ship draughts and speeds. The ship resistance, wave pattern, Kelvin angle and wave elevation at specific positions are investigated as functions of these parameters. Ship maneuvering is investigated using virtual captive model tests based on the MMG (Mathematical Maneuvering Group) model. An actuator disk is implemented to replace the real propeller. Open water test, rudder force test, OTT (Oblique Towing Tank test) and CMT (Circular Motion Test) of a KVLCC2 model are carried out to obtain the hydrodynamic coefficients of the propeller, rudder and ship hull. Using the obtained coefficients, system-based maneuvering simulations are carried out and validated using the free running test data. These studies reproduce real ship tests and thus prove the validity of our numerical models. As a result, the numerical solver is promising in ship hydrodynamics and marine engineering simulations
Mehal, Jean Elie. "Analyse de l'influence de rugosités organisées sur les écoulements cavitants instationnaires". Phd thesis, Ecole nationale supérieure d'arts et métiers - ENSAM, 2014. http://pastel.archives-ouvertes.fr/pastel-01062146.
Testo completoNdongo, Fokoua Georges. "Etude expérimentale de la réduction de traînée par injection de bulles". Thesis, Brest, 2013. http://www.theses.fr/2013BRES0095/document.
Testo completoThis work presents experimental study of drag reduction by injection of bubbles. Injection of bubbles into the developing boundary layer along the hulls of ships could help to reduce significantly the frictional resistance by lowering a fluid along the hull and interacting with the near-wall turbulent structures. We investigate the interactions between bubbles, the coherent motion and the viscous torque in a Taylor-Couette flow for outer cylinder at rest, while bubbles are injected constantly through a needle. The Reynolds number ranges up to Re≤20.104, for these values of the Reynolds number, Taylor vortices are persistent leading to an axial periodicity of the flow. Bubbles size varies between 0.05 and 0.12 times the width of the gap, depending on the needle and the liquid used. An original method for tracking bubbles in a meridian plane coupled with measures of overall torque applied to the inner cylinder helped to highlight two regimes of drag reduction and various types of arrangements of bubbles, depending on their size and Reynolds number. Bubbles could have a sliding motion, wavering, be captured by the Taylor cells or in the outflow areas near the inner cylinder. Characterization of the liquid velocity by PIV both in single phase and two-phase flow helped to study the modifications induced by the bubbles on the liquid phase and to discuss about the mechanisms involved in the changes induced by the bubbles in the overall torque. The study show that for the Reynolds number before the capture, bubbles could help to stabilize the flow in agreement to the reduction of the viscous torque up to -30% for lowest void fraction (<1%). For the Reynolds number after the capture, bubbles trapped by the Taylor cells lead to a reduction of the axial wavelength and increasing of the vorticity of the cells, associated to an increasing of the rms. This configuration leads to an increasing of the viscous torque. However, bubbles trapped in the outflow areas near the inner cylinder lead to an increasing of the axial wavelength, associated to a decreasing of the vorticity. The configuration supports a smaller reduction of the viscous torque than in the case without captured
Lerebours, Augustin. "Use of additive manufacturing techniques for the production of customized implants with complex geometry : application to reparative hand surgery". Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2531.
Testo completoOsteoarthritis is a pathology that causes the degeneration of joint surfaces. In the particular case of the trapezo-metacarpal joint, osteoarthritis irreversibly deforms the trapezium bone, causing loss of mobility and reduced grip strength coupled with pain at the base of the thumb. However, therapeutic solutions are not satisfactory with limited functional recovery resulting in a loss of quality of life for the patient. In the case of the hand, the personalization of implants seems to be relevant because of the great variability of the joint mechanical characteristics and the musculoskeletal specificities. This thesis work focuses on the methodology for creating a trapezio-metacarpal implant patient-matched, based on the potentialities of additive metal manufacturing technologies. More generally, it involves developing, analyzing and validating the steps involved in the manufacture of any complex geometric implant from medical imaging to implantation. The work initially focuses on identifying specific patient parameters in order to numerically "rejuvenate" the deformed bone in its pre-pathological stage to design the ideal implant and adapt the model to additive manufacturing (DfAM). Implant manufacturing and post-treatment are also studied from a biological (cytocompatibility, immune system response), mechanical (microstructure, friction property) and morphological (quantification of geometric deviations) point of view. The surgical implantation approach is addressed through various tests on cadavers to better integrate the benefits / risks for the patient. A study on the psychology of the patient suffering from rhizarthrosis and his expectations for a therapeutic solution concludes this manuscript. The results have led to 2 patents and the writing of 6 scientific articles