Дисертації з теми "Caoutchouc – Contraintes (mécanique) – Déformations (mécanique)"
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Carcan, Alain. "Modélisation des grandes déformations axisymétriques de membranes minces hyperélastiques incompressibles." Compiègne, 1985. http://www.theses.fr/1985COMPS134.
Повний текст джерелаWarneboldt, Iona. "Multiaxial fatigue design of elastomeric parts using Equivalent Fatigue Loads." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2022. http://www.theses.fr/2022ENTA0002.
Повний текст джерелаThis thesis introduces an Equivalent Fatigue Load (EFL) approach for the multiaxial fatigue design of elastomeric parts. As direct Finite Element Analysis (FEA) calculations of automotive in-service loads (Road Load Data (RLD)) are too expensive, the objective is to derive simplified load blocks as a realistic input for numerical damage calculations. Three streps are applied for this method: the localization method, the material damage function and the EFL determination process. Various fatigue tests have been conducted (415 samples) to study the fatigue behavior of this complex type of relaxing and non-relaxing multiaxial loading on natural rubber specimens. Lifetime and crack features are analyzed to eventually introduce an appropriate critical planebased fatigue measure and to establish a novel mean strain effect model. This criterion is generalized throughout an original critical plane search method. To estimate the local mechanical response (localization method), this thesis identifies an axes-coupling method that is fitted for the nonlinear nature of elastomeric structures. It is based on the multiplicative decomposition of the deformation gradient tensors. These two steps are then implemented in the framework of the EFLdetermination process. For this, a global optimization method is added to determine the simplified load blocks, causing locally the same fatigue behavior in the given structure. The computational costs of this optimization are reduced by only considering a subset of the most damaged material points for EFLdetermination. Finally, the method has been challenged on a specimen to outline its capabilities and to validate the approach
Courtois, Philippe. "Application des éléments cinématiques au calcul du forgeage de pièces en déformations planes ou axisymétriques." Lille 1, 1986. http://www.theses.fr/1986LIL10025.
Повний текст джерелаBuy, François. "Étude expérimentale et modélisation du comportement plastique du tantale : prise en compte de la vitesse de déformation et de l'histoire du chargement." Metz, 1996. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1996/Buy.Francois.SMZ9632.pdf.
Повний текст джерелаThe growing interest numerical results showing the response of structures to dynamic loading conditions implies the development of very sophisticated constitutive models. These models must take two points into account: transcribe a bunch of experimental facts and predict the behaviour of the material under specific loading conditions. Through the mechanical behaviour of tantalum, we tried to understand and describe the phenomena occuring in b. C. C. Metals. Plastic strain cannot be considered as a parameter describing the physical state of the material. Klepaczko's model based on the evolution of a single state parameter (the total dislocations density) fitted already fairly well with the experimental results for f. C. C. Metals. We performed quasistatic and dynamic torsion tests on high-purity polycrystalline tantalum at room temperature. Moreover, on the same type of samples, we performed jump tests in strain rate with Split Hopkinson Torsion Bars. Although Klepaczko's model can correctly fit our experimental results, the introduction of a second state parameter (the mobile dislocations density) seems necessary for a better understanding and restituion of the phenomena occuring during plastic flow. We present a proceeding to determine analytically the contributions to the flow stress of the microstructure and of the loading conditions (temperature and strain rate). Finally, we compare the results in compression and torsion. It appears that the kind of solicitation has a major role on the mechanical behaviour of tantalum which limits at present the proposed model
Estivalèzes, Erik. "Étude et développement d'un élément de poutre composite pour un revêtement déséquilibré." Toulouse, INSA, 1995. http://www.theses.fr/1995ISAT0002.
Повний текст джерелаLegrand, Laurène. "Etude linéaire et non linéaire de la déformation de fronts de fissures planes au cours de leur propagation et notamment de leur coalescence." Paris 6, 2011. http://www.theses.fr/2011PA066662.
Повний текст джерелаDursapt, Michel. "Contribution expérimentale de la métrologie des états de surface à l'étude du comportement des surfaces rugueuses soumises à l'action de contraintes mécaniques." Ecully, Ecole centrale de Lyon, 1999. http://www.theses.fr/1999ECDL0014.
Повний текст джерелаSaad, Patricia. "Modélisation et identification du comportement non linéaire des cales en caoutchouc." Ecully, Ecole centrale de Lyon, 2003. http://bibli.ec-lyon.fr/exl-doc/psaad.pdf.
Повний текст джерелаWe develop a numerical model to compute non linear rubber bush response. The objective is to take into account elasticity, damping, and non linear properties in a simple model dedicated to full vehicle modelling simulation. It is therefore important that the constitutive model a accurately capture theses aspects of the mechanical behaviour. To take into account these properties, Finite Element Codes use several complex constitutive laws. All these constituve equations can be integrated in finite element models and many algorithms are developed for this purpose. The main drawback of this procedure is its complexity. The number of dof is too high to be integrated in a vehicle study. Our work aims at giving a simplified approximation of the force as a function of the displacement and its derivatives, starting from a microscopic constitutive equation. Starting from a finite element model and a constutive law, we want to generate an equivalent rheological model, with a few dof. This model aims at predicting the frequency response of the bush, function of its geometry, of the load, of the parameters of the constitutive law. To do so, we approximate the displacement as a linear combination of admissible kinematic displacement fields, according to the Rayleigh-Ritz approximation. Hyperelastic models are used to fit on linear quasi static force deflection curves. Viscoelastic constitutive laws are also developped. In order to predict amplitude dependency observed when we measure steady state harmonic response, we use a Volterra development of the stress strain constitutive equation. To take into account preload effects, we linearize a viscohyperelastic model. The predictions of these models are compared to experimental data
Perrin, Henri-François. "Étude des déformations de pièces composites induites par le procédé d'infusion de résine." Paris, ENSAM, 2011. http://www.theses.fr/2011ENAM0041.
Повний текст джерелаThe dimensional instability of the composite parts limits the large diffusion of composites materials. It has to effect a shape complexity limitation and the increasing of the joined part number. This works is focused on the deformation induced by liquid resin infusion process. The main purpose is the characterization of the link between the product-processresources interactions and the final part shape. Experimental analyze on flat composite part has underlined a specific deformation mechanism, responsible of a majority of the transferred stress. The influence of industrialization parameters has been experimentally highlighted. Based on this experimental data, a prediction model has been established and his robustness has been evaluated. Than, the role of theses interactions in case of angled part has been investigated. Their contribution on the spring-in angle is minor compare to the intrinsic contribution such as the thermal and cure shrinkage anisotropies. Liquid resin infusion process can induce significant stress transfer into the part. This work represents a tool that enable a prediction of the deformation amplitude as function of number of industrialization parameters
Detraux, Jean-Michel. "Formulations et applications en grandes déformations des solides." Compiègne, 1985. http://www.theses.fr/1985COMPI199.
Повний текст джерелаBaz, Omar. "Quelques problèmes de flambement viscoélastique." Montpellier 2, 1990. http://www.theses.fr/1990MON20018.
Повний текст джерелаChehade, Rabih. "Contribution à l'étude du comportement des géomatériaux pulvérulents sous des solliciatations rotationnelles : Réalisation d'un appareillage de torsion." Lille 1, 1989. http://www.theses.fr/1989LIL10013.
Повний текст джерелаRingeval, Sylvain. "Microstructures et textures d'alliages d'aluminium déformés par forgeage croisé (compression multidirectionnelle)." Saint-Etienne, EMSE, 2006. http://www.theses.fr/2006EMSE0009.
Повний текст джерелаA new cross-forging device has been developed to enable high strain deformations up to 450°C. Its main advantage is the control of the deformation temperature by means of an original flip mechanism which avoids temperature variations between each compression. Cross-forging tests have been carried out on two polycrystalline aluminium alloys (AA 3103 and AlMgScZr) and on Al-0,3%Mn single crystals over large temperature and strain rate ranges, up to a cumulative strain of about 3. The results were characterised in terms of rheology, microstructures and textures, and a comparison with plane strain compression tests established. Original 3D texture simulations (Taylor model combined with a grain interaction scheme) enabled us to explain some experimental results, namely the rapid stress saturation observed for the polycrystalline alloys strained below 200°C, and the appearance during the test of three texture components (unit cell flip of 45° around each of the three axes)
Gharzeddine, Fadi. "Formulation de la plasticité en grandes déformations et son implantation numérique." Compiègne, 1999. http://www.theses.fr/1999COMP1198.
Повний текст джерелаLaghmach, Rabia. "Modélisation de la cristallisation des élastomères sous sollicitation mécanique par champ de phase." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0061/document.
Повний текст джерелаNatural rubber NR and more generally elastomer presents unique physical properties that are very important for many engineering applications. Strain induced crystallization of elastomer presents a major interest because it improves considerably the mechanical properties. In fact, the presence of crystallites within the amorphous phase in a polymer network induces a strengthening of this material, giving NR a self-reinforcement character. In this thesis, we develop a mesoscopic model to describe the crystallization of elastomers under strain. In this context, we present a kinetic model using a new physical approach: a phase field model. This model combines the crystallization thermodynamics with the local stress field. The thermodynamic description of the phase transition is based on a Gibbs free energy functional F which contains all energy contributions of the system: the bulk contributions (enthalpy and entropy) and surface tension. To understand the experimental observation of nanometer size crystalites, an explicit account of the topological constraints induced by both entanglements and/or crosslinks is necessary. We investigated two limiting mechanisms, a kinetic limitation of the growth, and an energetic limitation. Based on both the kinetic and the energetic approaches, we have systematically studied the influence of topological constraints on the growth process. We have shown that the growth process is affected by the accumulation of elastic stress at the interface. The kinetic model predicts the existence of instabilities during the growth. These instabilities induce a heterogeneous dynamical growth which leads to the formation of dendrite like structures. On the contrary, the energetic approach predicts an exponential increase of the surface tension during the growth that limits the size of the crystallites very efficiently. In the last part we investigated elastomer crystallization under cyclic deformation. To this end, we coupled the previous energetic model with the nucleation process. Finally the simulation data are compared with experimental measurements
Boucherif, Abderraouf. "Elaboration de pseudosubstrats accordables en paramètre de maille à base de silicium mésoporeux pour l'hétéroépitaxie." Lyon, INSA, 2010. http://theses.insa-lyon.fr/publication/2010ISAL0082/these.pdf.
Повний текст джерелаThis work assesses the potentiality of Porous Silicon (PS) as a mechanical straining substrate for modifying the lattice parameter of IV-IV semiconductor thin films (Si or SiGe). The aim is either to tune the optoelectronic properties of the thin film, or to adapt the film lattice parameter to that of other materials like SiGe, Ge, or GaAs. Such a film can be used as a seed layer for the heteroepitaxial growth of lattice mismatched materials such as SiGe, Ge or GaAs on silicon with a high crystalline quality. In short, the (thin film) / (porous silicon) heterostructure constitutes a « lattice tunable virtual substrate » obtained from a low cost substrate, viz, the porous silicon. The development of a “two wafers technique” has been a true breakthrough as it made it possible to obtain a IV-IV semiconductor film as thin as 50 nm, with large lateral dimension (2"), strictly constant thickness, exempt of structural defects and with a perfectly smooth and clean surface. Moreover, this ultra-thin film can be easily handled and its lateral dimension is only dependant on the diameter of the anodization cell. Low temperature thermal oxidation of the bulk porous Si substrate induces its volume expansion, which leads to a straining of the thin film on top. The control of oxidation parameters allows obtaining highly strained (above 1%) films without any structural defects. The technique makes the film lattice in-plane parameter closer to that of Ge or GaAs, which is a step forward toward their integration on silicon
Andriamitantsoa, Lucien. "Approche ultrastructurale de la mécanosorption sur le Pin maritime." Bordeaux 1, 1988. http://www.theses.fr/1988BOR10548.
Повний текст джерелаDelost, Matthieu. "Analyse théorique et numérique pour des problèmes quasistatiques régularisés de contact avec frottement." Nice, 2004. http://www.theses.fr/2004NICE4112.
Повний текст джерелаOur interest lies in the bilateral contact between a deformable elasto-visco-plastic solid and a rigid foundation, with Tresca or Coulom friction law. Existence results (and uniqueness results for Tresca law) for associated variational problems are classical. Nevertheless, they are not valid anymore in the frame of aour study, for we have regularized a term in the inequations. We first present the physical background and the mathematical tools related to the problems. We then settle a constructive method for the analysis of variational inequalities involving a regularized convex term. Thus, we obtain existence and uniqueness results, asymptotic convergence results and approximation result concerning theoretical numerical analysis. Then we apply those results to bilateral contact problems involving Tresca or Coulomb friction law. Finally, we present numerical results, in which we compare two ways to compute time discretization and we study the influence of different parameters on the calculus of solutions
Richeton, Julien. "Modeling and validation of the finite strain response of amorphous polymers for a wide range of temperature and strain rate." Université Louis Pasteur (Strasbourg) (1971-2008), 2005. http://www.theses.fr/2005STR13159.
Повний текст джерелаMrabet, Kaïs. "Comportement mécanique en grandes déformations du polyéthylène haute densité : approche thermodynamique de l'état relaxé." Vandoeuvre-les-Nancy, INPL, 2003. http://www.theses.fr/2003INPL036N.
Повний текст джерелаThe semicrystalline polymers are the subject of many scientific researchs aiming to understanding their microscopic mechanisms of deformation. Nevertheless, the modelling which we currently find in the literature do not approach the mechanical tests with unloading or the cyclic tests at large strains. Among the reasons of these insufficiencies appears themultiplicity of the internal reorganization processes which is seldom described finely in the physical modelling. Moreover, a main aspect of the semicrystalline polymer behaviour is often ignored, it acts of the relaxed state. Within the framework of formalism Distribution of Non Linear Relaxation (D. N. L. R. ), we are interested more closely in these two aspects of the mechanical behaviour: multiplicity of the mechanisms, relaxed state. To clarify these two concepts, the objective was to characterize the relaxed state at large strains and to propose a physical modelling based on the thermodynamics of irreversible processes and on the microscopic aspects of the deformation. The distribution of the weights of the various modes has been described following observations given by a clip tests. The material used is the High Density Polyethylene HOPE. The tests were carried out with VideoTraction technology. The relaxed state modulus measured during tension loading is definitely more important than that of the unloading, which translates a damage phenomenon. The irreversibility of the relaxed state imposes that the modelling must use a functional formulation which integrates the memory effect and damage. In addition, the dip test has shawn the presence of mechanical cross over. A bibliographical study showed that this phenomenon is closely related to the processes multiplicity. Thus, we have shawn that the modal partition adopted in practice has to be re-examined. We have shawn that the modelling set up is able to reproduce complex loadings, in particular the cyclic tests with relaxation, and to predict behavior very depending on the. Loading history and the irreversible relaxed state
Berrehili, Abdelmoutalib. "Comportement cyclique et tenue en fatigue sous chargement multiaxial d'un polyéthylène : expériences et critère d'endurance." Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aéronautique, 2010. http://tel.archives-ouvertes.fr/tel-00517401.
Повний текст джерелаAhmed, Said Abdallah. "Contribution à l'étude des effets thermiques et des déformations dans les butées hydrodynamiques à géométrie fixe." Poitiers, 2008. http://theses.edel.univ-poitiers.fr/theses/2008/Ahmed-Said/2008-Ahmed-Said-These.pdf.
Повний текст джерелаThe influence of thermal effects and solid deformations on the performance of hydrodynamic fixed geometry thrust bearings is analyzed. Previous studies on fixed geometry hydrodynamic thrust bearings combining thermal effects and deformations are scarce. After the presentation of the theory of thermohydrodynamic (THD) lubrication, we describe the methods of deformation calculations. The thermoelastohydrodynamic (TEHD) study, which takes into account the local thermal effects and the solid deformations, is carried out on an eight pad fixed geometry hydrodynamic thrust bearing. The hydrodynamic pressure and temperature fields are obtained by the mean of the finite difference method and the pad and collar displacement fields are computed using the finite element method. We also take into account the runner deformations in order to solve the TEHD problem. The influence of the operating conditions (applied load and rotation speed) on the various characteristics of the thrust bearing is also analyzed. We showed that mechanical deformations of the runner were found very significant for an accurate prediction of the performance of the thrust bearing
Hossain, Tasnia. "GaN based structures on patterned silicon substrate : stress and strain analysis." Nice, 2012. http://www.theses.fr/2012NICE4096.
Повний текст джерелаLe présent travail concerne l’étude des contraintes et des déformations dans le matériau GaN épitaxié par EJM et par EPVOM sur substrat silicium texturé en vue d’éviter la fissuration du matériau et ainsi obtenir des motifs compatibles avec la réalisation de composants (DELs, Lasers, transistors etc. ). Nous avons étudié des motifs différents en tailles, séparations, hauteurs de tranchées, formes, orientations dans le plan ainsi que deux orientations cristallines du substrat silicium. Au-delà d’une épaisseur critique du film déposé, pour une forme de motif donnée, la fraction de motifs fissurés augmente avec la taille des motifs. 88% des motifs en losange et 96% des motifs carrés sont exempts de fissures pour des films GaN épais de 12 μm pour une largeur égale à 200 μm. Une distribution en U de la contrainte en tension est mise en évidence par spectroscopie micro-Raman et par micro-photoluminescence pour les différentes tailles de motifs étudiés, le maximum de contrainte se situant en leur centre et la contrainte se relaxant graduellement vers les bords libres. La contrainte augmente avec la taille des motifs, mais diminue avec la hauteur des tranchées réalisées dans le substrat. Un modèle analytique a été adapté pour rendre compte de la répartition des contraintes. La distance séparant les motifs influe peu. Quoi que la répartition des contraintes puisse être différente durant la croissance, nous avons montré la possibilité d’obtenir des films de GaN avec une bonne qualité cristalline sur ces motifs, ce qui montre que cette voie est prometteuse pour la fabrication de composants optoélectronique et électroniques jusqu’ici limités par la croissance sur substrat planaire
Tié, Bi Grah Robert. "Etudes expérimentales des couplages thermomécaniques par méthodes optiques et par thermographie infrarouge, applications aux polymères." Poitiers, 2000. http://www.theses.fr/2000POIT2282.
Повний текст джерелаBrusselle, Nadège. "Comportement viscoélastoplastique d'un polymère semi-cristallin avant la striction : caractérisation expérimentale et modélisation phénoménologique." Compiègne, 2000. http://www.theses.fr/2000COMP1317.
Повний текст джерелаFournier, dit Chabert Florent. "Rechargement laser d'un superalliage à base de nickel : étude expérimentale et modélisation de l'endommagement." Nantes, 2007. http://archive.bu.univ-nantes.fr/pollux/show.action?id=330065e9-7ae3-4911-82fe-f88903d7fb03.
Повний текст джерелаLaser metal cladding is a welding-like process, in particular used to rebuild the shape of aeronautical components made of nickel based superalloys. Interdendritic cracks are systematically observed inside the repaired zone. After a metallurgical study of the damage, the hypothesis of an embrittlement by interfacial sulphur segregation has been confirmed by two techniques: Auger electron spectroscopy and electron probe micro-analysis. The ability of the latter to detect and quantify interfacial segregations has been demonstrated in the study. A fine modelling of the thermal aspects of the process and of interfacial segregation, using finite elements, allowed to show that sulphur segregation could not be avoided. In particular, it has been shown, using numerical simulation, that is not possible to control interfacial segregation through the adjustment of process parameters (laser power and velocity). Furthermore, welding processes are known to generate important residual stresses and plastic strains. A tensile residual stress state in the repaired zone, associated to important plastic strains, has been simulated using finite elements. It is responsible of the cracking of interdendritic boundaries embrittled by important quantities of sulphur. Finally, a parametric study of the process parameters (laser power and velocity) has been performed and has led to a solution to the cracking problem
Politano, Olivier. "Simulations mésoscopiques de la déformation plastique des monocristaux C. F. C. Sous contrainte." Dijon, 1999. http://www.theses.fr/1999DIJOS066.
Повний текст джерелаVerreault, Nicolas. "Étude des contraintes et des déformations induites thermiquement dans des tubes en matériau composite." Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26032.
Повний текст джерелаMin, Kyung-Tak. "Optimisation d'un cylindre en sandwich composite soumis à des sollicitations combinées." Compiègne, 1985. http://www.theses.fr/1985COMPI201.
Повний текст джерелаDiouf, Boubakar. "Analyse statistique de l'évolution de l'endommagement dans des matériaux hétérogènes." Le Mans, 2005. http://cyberdoc.univ-lemans.fr/theses/2005/2005LEMA1019.pdf.
Повний текст джерелаThe objective of this work was to implement a simulation procedure for evaluating damage development through test specimens constituted of heterogeneous materials subjected to different types of loading. The procedure is based on the evaluation of stress and strain fields using finite element analysis and then considering a statistical distribution of fracture criterion through test specimens. Also, it is considered that it exists a characteristic dimension of damage growing which is kept constant. The results obtained show that the damage development is clearly different according to whether the conditions of loading induce a homogenous stress field or a strong stress gradient. In the two types of stress fields, the lower limit and the distribution of fracture stresses scattering are the essential characteristics which govern progression of damage. A digital twin Mach-Zehnder holographic interferometer was applied to the analysis of the follow-up of cracking in a synthetic concrete submitted to three-point bending tests and results allow to derive the parameters necessary to evaluate the progression of cracking using the simulation procedure
Manchuel, Kévin. "Étude sismotectonique de la marge active Nord Equateur-Sud Colombie : à partir des données de la campagne de sismologie passive ESMERALDAS." Nice, 2010. http://www.theses.fr/2010NICE4099.
Повний текст джерелаFournet, René. "Etude de la formation de structures dislocatives dans des monocristaux sous contraintes mécaniques : approches analytique et numérique." Dijon, 1994. http://www.theses.fr/1994DIJOS050.
Повний текст джерелаGhfiri, Rachid. "Etude du retard à l'amorçage et à la propagation d'une fissure de fatigue après perçage d'un trou avec et sans expansion." Lille 1, 2000. http://www.theses.fr/2000LIL10146.
Повний текст джерелаDans ce travail, trois degres d'expansion ont ete analyses (de = 1. 7%, 3. 4% et 4. 3%). L'expansion du trou ameliore considerablement la duree de vie qui augmente avec le degre d'expansion. Par ailleurs, l'effet du chargement sur le nombre de cycles a l'amorcage est etudie. Ce dernier augmente quand l'amplitude du facteur d'intensite de contrainte diminue. L'analyse des facies de rupture par microscope electronique a balayage montre une zone comprimee au bord du trou et une absence des microfissures. Par contre, loin de cette zone des microfissures orientees dans tous les sens ont ete observees. Une modelisation numerique par elements finis est realisee afin de quantifier les contraintes residuelles de compression ainsi que la zone affectee par l'expansion au bord du trou
Stoehr, Michèle. "Epitaxie par MOVPE de ZnSe sur des substrats semiconducteurs et études des contraintes dans ces hétérostructures." Montpellier 2, 1991. http://www.theses.fr/1991MON20301.
Повний текст джерелаBordeleau, Charles-Antoine. "Effet des charges lourdes sur les barrages en remblai : déformation permanente d'un noyau d'argile." Master's thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/69366.
Повний текст джерелаLu, Jian. "Mesure de la distribution des contraintes résiduelles par la méthode du trou incrémentale." Compiègne, 1986. http://www.theses.fr/1986COMPD045.
Повний текст джерелаFardoun, Farouk. "Etude de la déformation plastique cyclique des aciers inoxydables austénitique, ferrique et duplex, par analyse des boucles d'hystérésis : contraintes internes et effectives." Lille 1, 1997. http://www.theses.fr/1997LIL10157.
Повний текст джерелаBourgeois, Myriam. "Étude du comportement viscoplastique à 773 K d'alliages de titane biphasés Ti-6246." Compiègne, 1997. http://www.theses.fr/1997COMPD984.
Повний текст джерелаKang, Chi-Hang. "Une famille d'éléments hybrides singuliers pour l'étude des plaques fissurées métalliques et composites." Compiègne, 1991. http://www.theses.fr/1991COMPD362.
Повний текст джерелаBrantut, Nicolas. "Couplages thermo-hydro-mécaniques et chimiques lors de la rupture et du glissement sismiques." Paris 7, 2010. http://www.theses.fr/2010PA077245.
Повний текст джерелаDeformation tests on gypsum at 25 and 70°C show that strain is localized in shear bands, formed by a mixture of brittle and plastic processes. Shear banding is slow at room temperature whereas it is dynamic at 70CC. This acceleration of the deformation with increasing temperature could be explained by a thermal activation of plasticity. In heating tests up to I50°C, above the dehydration temperature of gypsum , the samples undergo a strong compaction, which is associated with a large acoustic activity. During the reaction, the Poisson's ratio of the rock decreases, due to microcracks accumulation and phase change. A theoretical analysis of thermo-hydro-mechanical and chemical couplings during nucleation and seismic slip demonstrates that the enclothennic character of dehydration reactions is responsible for a strong thermal buffering of the plane, even if the slip rate is high. This prediction is confirmed by experimental high-velocity friction tests on gypsum. In addition, the stability analysis of a theoretical fault model shows that dehydration reactions can clestabilize a normally (i. E. When no reaction occurs) stable fault, which can potentially lead to an earthquake. The work summarized in this thesis shows a great complexity of the mechanical behaviour of thermally unstable rocks; it emphasizes the importance of a good knowledge of fault rocks lithology and mineral composition, which is often overlooked by seismologists. This complexity is probably responsible for the great variety of earthquakes observed in nature (e. G. Slow or silent slips, low frequency events. Non-volcanic tremors. . . )
Mondal, Richard. "Une formulation d'éléments finis pour l'analyse de plaques minces et épaisses en matériaux composites." Compiègne, 1985. http://www.theses.fr/1985COMPI194.
Повний текст джерелаPierre, Philippe. "Critères d'instabilité plastique. Influence de gradients de contraintes dans l'épaisseur des tôles embouties." Paris 6, 1990. http://www.theses.fr/1990PA066650.
Повний текст джерелаRisbet-Voitot, Marion. "Influence de l'état métallurgique et d'un gradient de contraintes sur le critère d'endurance (critère de Dang Van) d'un superalliage à base nickel." Compiègne, 2002. http://www.theses.fr/2002COMP1436.
Повний текст джерелаBelmahjoub, Faycal. "Comportement thermomécanique de matériaux métalliques sous divers trajets de chargement uniaxe." Montpellier 2, 1990. http://www.theses.fr/1990MON20153.
Повний текст джерелаFaivre, Sanja. "Landforms and tectonics of the Velebit mountain rance (Outer Dinarides, Croatia)." Clermont-Ferrand 2, 2000. http://www.theses.fr/2000CLF20005.
Повний текст джерелаAubry, Agnès. "Mesure, par diffraction des rayons X, des contraintes résiduelles dans les couches d'oxyde : application au système Ni/NiO." Compiègne, 1985. http://www.theses.fr/1985COMPI193.
Повний текст джерелаLestrade, Laurent. "Etude de la fusion superficielle au four solaire de barrières thermiques ZrO2-Y2O3 projetées par plasma." Perpignan, 1996. http://www.theses.fr/1996PERP0241.
Повний текст джерелаLamy, Michael. "Modélisation mécanique du cerveau de rat : application au traumatisme cérébral." Strasbourg, 2011. http://www.theses.fr/2011STRA6150.
Повний текст джерелаTraumatic brain injuries (TBI) are a major cause of deaths and disabilities in our societies. They often result from falls or motor vehicle collisions, when the head sustains a mechanical loading. Studying those injuries is a crucial issue; but the criteria governing the occurrence of said lesions remain not well known, as brain injuries are in essence the results of unforeseeable events, and thus can only be analyzed a posteriori. Therefore, the current work of thesis aimed to deal with brain injuries through a combined approach of experimental animal protocols and numerical models. In a first step, a finite element model (FEM) of the rat brain is developed. Based upon medical imaging, a detailed mesh of the brain is achieved, representing several main anatomical components; then, a mechanical characterization is defined. After a phase of validation and parametric tests, the model is used to simulate experimental protocols in which the rat head sustains angular accelerations loadings. Experimental results and numerical responses from the FEM were confronted to each other, to contribute to the knowledge on brain injury mechanisms. The first set of simulations deals with loadings related to mild TBI. New mechanical indicators are proposed, and prove to be better correlated with animal behavioral deficits than the usual mechanical parameters (stresses and strains). The second group of simulations focuses on loadings responsible for moderate to severe TBI. By comparing anatomical and histological data to numerical results, new thresholds are proposed, concerning Von Mises stresses and first principal strains levels, for the occurrence of severe TBI
Clérivet, Alain. "Contribution à la modélisation des mécanismes d’ouverture des fissures soumises à des sollicitations cycliques dans des alliages d’aluminium." Compiègne, 1986. http://www.theses.fr/1986COMPE049.
Повний текст джерелаPlancher, Emeric. "Mesures de champs de déformations élastique et totale pour la détermination du comportement mécanique local de matériaux cristallins." Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0056/document.
Повний текст джерелаThe prediction of damage occurring in metallic materials is dependent on the knowledge of the mechanical behavior at a micron scale. Crystal plasticity laws are often used to describe the behavior of a single grain in polycrystals. Such laws include many parameters which should be tuned according to the metallurgical and mechanical state of the material.An original way to identify theses parameters is presented in this work. The local constitutive behavior is measured at the local scale. It is used to adjust the parameters’ value on a single point calculation without the need for a finite element mesh. To observe the local behavior two types of full filed measurements are carried out: (i) stress measurements using diffraction-based Laue microdiffraction and high angular resolution EBSD – HR-EBSD – and (ii) strain measurements by digital image correlation.To ensure trustworthy results, the accuracy of Laue microdiffraction (Laue-DIC) and HR-EBSD measurements are determined for the first time in a plastically deformed material. Then, stress and strain fields are monitored at the surface of a single crystal bent in-situ in the low deformation regime (0.5%). The local behavior is determined and used to identify two parameters of a crystal plasticity law, in a 316L stainless steel single crystal