Tesis sobre el tema "Déformations (mécanique) – Simulation, Méthodes de"
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Germain, Jacques. "Contribution à l'étude du champ de déformations par granularité laser en élastoplasticité grandes déformations". Montpellier 2, 1995. http://www.theses.fr/1995MON20223.
Texto completoVanoverberghe, Laurent. "Anticipation des déformations lors du traitement thermique de pignons de boîte de vitesses". Paris, ENMP, 2008. http://pastel.archives-ouvertes.fr/pastel-00004771.
Texto completoTwo main strategies exist to manufacture gears, depending the respective order of finishing and heat treatment. Renault mainly uses a process where heat treatment follows finishing. Due to this, gear tooth distortion can not be corrected after quenching and thus has to be analysed in detail. Regardless of these two strategies, production development can be divided in two phases : process set up and series production. Each phase has its own problem. For the first, it will be useful to know beforehand the distortion during heat treament and other steps. We present some current phenomenological models of heat treatment process. A list of input parameters is done. Next, the use of numerical simulation is examined. A good qualitative correlation is observed between numerical and experimental results. Nevertheless, due to the complexity of input data and the determination of boundary conditions, another methodology is proposed structured around a data base containing the deformations of all gears manufactured in the factories. This methodology is implemented in a software and used at all Renault locations. Once this set up is finished, the part enters into series production. A second problem occurs : the nominal process deviation. For example, slight material changes, variations in machining conditions, modifications of heat treatment and so on can be responsible for these deviations. We mainly focuse here on dimensional deviations but this method could be applied to other ones. When production is stopped, these deviations have to be rapidly identified. This is why we propose here the methodology fundamentals to recognise the deviation origin from the part deformation. A numerical basis of all the deviations is created by applying a Proper Orthogonal Decomposition on numerical simulations. The projection of the real part deformation on this basis can help us to identify the deviation origin and so reduce time needed to analyse the problem
Malal, Nour-Eddine. "Modélisation et simulation numérique du comportement thermomécanique d'alliages métalliques". Montpellier 2, 1992. http://www.theses.fr/1992MON20115.
Texto completoDesobry, David. "Génération de maillages hexaédriques pour des simulations de grandes déformations". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0163.
Texto completoThis thesis focuses on the development of hexahedral meshing methods suitable for large deformation simulations in non-linear mechanics. Domain parameterization methods based on frame fields are used to generate high-quality hexahedral meshes aligned with the domain boundaries. However, during large deformations, the mesh quality may degrade and potentially block the simulation. This thesis explores the idea of determining an optimal connectivity for the mesh elements while taking into account the anticipated deformations.In 2D, a complete pipeline is developed to tackle this challenge by combining previous work and scientific contributions. In 3D, contributions are made to approach this objective, particularly by controlling the boundary valences of hexahedral meshes produced from frame fields. The different parts of the thesis address the steps of large deformation numerical simulations, the advantages of global parameterization methods, the results of simulations on industrial 2D meshes, and contributions to improving the flexibility and robustness of the hexahedral meshing process.The ultimate goal is to reduce the time spent by engineers in generating an adequate mesh for a simulation by considering a priori information on the deformation to which the mesh and the object will be subjected
Schwartz, Jean-Marc. "Calcul rapide de forces et de déformations mécaniques non-linéaires et visco-élastiques pour la simulation de chirurgie". Thesis, Université Laval, 2003. http://www.theses.ulaval.ca/2003/21208/21208.pdf.
Texto completoThis work presents a method for the fast computation of mechanical deformations and forces for the simulation of surgical applications. Surgery simulation aims at providing physicians with tools allowing extensive training and precise planning of given interventions. The design of such simulation systems requires accurate geometrical and mechanical models of the organs of the human body, as well as fast computation algorithms suitable for real-time conditions. Most existing simulation systems use very simple mechanical models, based on the laws of linear elasticity. Numerous biomechanical results yet indicate that biological tissues exhibit much more complex behaviour, including important non-linear and visco-elastic effects. For this reason, we developed a method allowing the fast computation of mechanical deformations and forces including non-linear and visco-elastic effects. This method uses finite element theory and has been constructed as an extension of the so-called tensor-mass algorithm for linear elasticity. It consists in pre-computing a set of tensors depending on the geometrical and mechanical properties of each finite element, which are later combined in the simulation part itself. Our non-linear model does not assume any particular form of mechanical law, so that the proposed method is generic enough to be applied to a wide variety of behaviours and objects. Following the description of the algorithm, of its performances in terms of computation time, and of its numerical stability conditions, we show that this method allows to reproduce the mechanical behaviour of a biological soft tissue with good precision. As this project is part of a broader effort aiming more specifically at developing a simulation system for liver cryosurgery, we experimentally characterized the properties of liver in perforation by a biopsy needle. The non-linear and visco-elastic tensor-mass model constructed from experimental parameters succeeded in accurately reproducing the observed properties.
Gharzeddine, Fadi. "Formulation de la plasticité en grandes déformations et son implantation numérique". Compiègne, 1999. http://www.theses.fr/1999COMP1198.
Texto completoRivaux, Benjamin. "Simulation 3D éléments finis des macroségragations en peau induites par déformations thermomécaniques lors de la solidification d'alliages métalliques". Paris, ENMP, 2011. https://pastel.archives-ouvertes.fr/pastel-00637168.
Texto completoMacrosegregations are chemical heterogeneities either in the skin or in the center of metallurgical products. These heterogeneities can generate serious troubles during downstream processing. Contrary to other studies which focus on central macrosegregation, our work aims to simulate the skin macrosegregation induced by thermomechanical deformations. Three steps are necessary to build the simulation. The first step consists on simulating macrosegregation at rigid and fixed solid, i. E. Without solid deformation. The second step, independent of the first one, aims to simulate the deformation of the solid without macrosegregation. The last step is a combination of the two previous one. All equations are solved by stabilized finite element methods. Each step refers to experiments in order to compare numerical and experimental results. The first step reproduces numerically the macrosegregation observed during Hebditch & Hunt experience. The numerical results are in good agreement with the experimental ones. The second step aims to simulate the deformation of a metallic liquid droplet during its solidification in contact with a copper chill, in microgravtiy. The numerical deformation obtained presents the same trend as the experimental one but in a lower magnitude. The last step is based on El-Bealy experience consisting of a pulsed water cooling of an ingot. The results show concentration variations but the simulation does'nt catch all experimental ones. Computations without macrosegregation point out that our simulations are less sensitive of deformation than the experiment. All simulations were run with binary alloys. Computations have also been run to simulate ternary alloy solidification but without solid deformation
Khelifa, Mourad. "Simulation numérique de l'endommagement en formage de structures minces". Troyes, 2004. http://www.theses.fr/2004TROY0013.
Texto completoThis work deals with the study of a advanced approach for the modelling and the numérical simulation of sheet metal forming processes in order to optimize their technological parameters with respect to the ductile damage occurence. The strong coupling between the anisotropic plastic behaviour with mixed kinematic and isotropic hardening and the ductile damage based on the thermodynamics of the irreversible processes with state variables is used. The theoretical and numerical aspects of the used formulation are described in details. The numerical integration of the model using and iterative implicite scheme combined with the radial return mapping and the reduction of the number of equations is discussed. The equilibrium equations are solved by means of a Static Implicit scheme (SI) or a Dynamic Explicit scheme (DE). An exerimental Database, essentially constitued of specimen tensile tests, is used to identify the model's paramters. In order to validate and to show the strength of the employed methodology to predict with accuracy the damaged zones, numerical simulations of simple and complex sheet metal forming processes are performed. A comparison with experimental results provided by CETIM and ENIM are then carried out. Another comparison between the present methodology and the inverse approach (URCA/GMMS) is also made on some cases
Liu, Xiao Jing. "Modélisation des grandes déformations élasto-plastiques de coques axisymétriques". Compiègne, 1992. http://www.theses.fr/1992COMPD513.
Texto completoAchor, Zyad Khalid. "Étude du comportement élastoviscoplastique d'un polycarbonate à grande vitesse de déformation : simulation numérique du cisaillement adiabatique". Metz, 1999. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1999/Achor_Zyad.Khalid.SMZ9932.pdf.
Texto completoArruffat-Massion, Roxane. "Modélisation des textures et de l'écrouissage dans le procédé d'extrusion angulaire à section constante". Metz, 2004. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2004/Arrufat_Massion.Roxane.SMZ0430.pdf.
Texto completoEqual channel angular extrusion (ECAE) causes a very detailed attention these last years. This process has developed by Segal in 1974 to achieve severe plastic deformation without changing the sample dimensions. By this technique the material can be hardened near to its theoretical limit, at the same time, a very fine microstructure develops (consisting of near nano-crystals). A new analytical model is presented by using a flow function to describe the material deformation in ECAE. Validated by finite element calculations, this new approach allows the simulation of crystallographic textures with polycrystalline plasticity approaches (two models were employed: self-coherent and Taylor). Detailed comparisons were made with experimental textures for copper and aluminium for various ways of deformation (route A, B and C, characteristic of the ECAE). It was shown that the new model describes the evolution of the textures better than earlier approaches like the model of discontinuous shearing. The flow line approach is incorporated into a hardening model based on the dislocation cell structure of the metal. In this way strain hardening is modelled in a fully analytic way up to large strains. The evolution of the crystallographic texture was taken into account with the help of Taylor factors obtained from self consistent viscoplastic polycrystalline simulations. The model calculations led to good agreements with the experimental curves for the material considered (OFHC copper)
Temimi-Maaref, Nadia. "Comportement thermo-mécanique et rupture de polypropylènes. Etude expérimentale et modélisation". Phd thesis, École Nationale Supérieure des Mines de Paris, 2006. http://tel.archives-ouvertes.fr/tel-00188389.
Texto completoFouial, Karim. "Nouvelle méthode d'interprétation des mesures des contraintes par surcarottage adaptée aux roches à comportement non linéaire ou fracturées". Vandoeuvre-les-Nancy, INPL, 1997. http://www.theses.fr/1997INPL109N.
Texto completoBude, Jérémie. "Ductile fracture simulation using the strong discontinuity method". Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2243/document.
Texto completoIn the context of loadings criticality analysis, the thesis work have the following objectives : to take into account the underlying phenomena to ductile fracture : the volumetrie (plasticity and damage) and surfacic (fracture) dissipativ mechanisms. We also aim at regularizing the solution with regards to meshing, predicting the transition from a straigh crack propagation to a slant fracture mode observed for certain tests. The chosen method relies on the stron discontinuity method. One of the major challenges of this work is to extend its framework to the ductile fractur modeling framework, by accounting for plasticity and damage in the bulk. The first part of this work is dedicated to th establ'ishment of a model in small strain hypothesis, with a material model that takes into account coupied plasticity an damage in the QUik and a damageable model for the cohesive surfacic behavior. Both modes 1 and Il have been taken int) account in thnumerical examples. Results attesting the regularizing capabilities of the method are presented fo different tests. The second part of this work is dedicated to the formulation of a finite strain mode!, and results showin the good regularizing capabilities of the method are also shown. Both elements have been implemented in FEAP (Finit Element Analysis Program), an academie software developed at UC Berkeley by Taylor, and more recently in the finit element software Abaqus
Shakourzadeh, Bolouri Hossein. "Modélisation des structures-poutres tridimensionnelles à parois minces et simulation du comportement non linéaire géométrique et élasto-plastique". Compiègne, 1994. http://www.theses.fr/1994COMPD773.
Texto completoAder, Thomas. "Les tremblements de terre de l'Himalaya : vers un modèle physique du cycle sismique". Paris 7, 2013. http://www.theses.fr/2013PA077282.
Texto completoHome to hundreds of millions of souls and land of excessiveness, the Himalaya is also the locus of a unique seismicity whose scope and peculiarities still remain to this day somewhat mysterious. Having claimed the lives of kings, or turned ancient timeworn cities into heaps of rubbles and tains, earthquakes eerily inhabit Nepalese folk tales with the fatalistic message that nothing lasts forever. From a scientific point of view as much as from a human perspective, solving the mysteries of Himalayan seismicity thus represents a challenge of prime importance. Documenting geodetic strain across the Nepal Himalaya with varions GPS and leveling data, we show that unlike other subduction zones that exhibit a heterogeneous and patchy coupling pattern along strike, the last hundred kilometers of the Main Himalayan Thrust fault, or MHT, appear to be uniformly locked, devoid of any of the "creeping barriers" that traditionally ward off the propagation of large events. The approximately 20 mm/yr of reckoned convergence across the Himalaya matching previously established estimates of the secular deformation at the front of the arc, die slip accumulated at depth has to somehow elastically propagate all the way to the surface at some point. And yet, neither large events from die past nor currently recorded microseismicity nearly compensate for the massive moment deficit that quietly builds up under die giant mountains. Along with this large unbalanced moment deficit, die uncommonly homogeneous coupling pattern on die MHT raises the question of whether or not the locked portion of die MHT can rupture all at once in a giant earthquake. Univocally answering this question appears contingent on die still elusive estimate of the magnitude of the largest possible earthquake in the Himalaya, and requires tight constraints on local fault properties. What makes the Himalaya enigmatic also makes it the potential source of an incredible wealth of information, and we exploit some of the oddities of Himalayan seismicity in an effort to improve the understanding of earthquake physics and cipher out the properties of die MHT. Thanks to the Himalaya, the Indo-Gangetic plain is deluged each year under a tremendous amount of water during the annual summer monsoon that collects and bears down on the Indian plate enough to pull it away from the Eurasian plate slightly, temporarily relieving a small portion of die stress mounting on the MHT. As the rainwater evaporates in the dry winter season, die plate rebounds and tension is increased back on the fault. Interestingly, the mild waggle of stress induced by the monsoon nains is about die same size as that from solid-Earth tides which gently tug at the planets solid layers, but whereas changes in earthquake frequency correspond with the annually occurring monsoon, there is no such correlation with Earth tides, which oscillate back-and-forth twice a day. We therefore investigate die general response of the creeping and seismogenic parts of MHT to periodic stresses in order to link there observations to physical parameters. First, the response of die creeping part of the MHT is analyzed with a simple spring-and-slider system bearing rate-strengthening rheology, and we show that at the transition with die locked zone, where the friction becomes Wear velocity neutral, the response of the slip rate may be amplified at some periods, which values are analytically related to the physical parameters of die problem. Such predictions therefore hold the potential of constraining fault properties on the MHT, but still await observational counterparts to be applied, as nothing indicates that the variations of seismicity rate on die locked part of the MHT are the direct expressions of variations of the slip rate on its creeping part, and no variations of die slip rate have been singled out from die GPS measurements to this day. When shifting to die locked seismogenic part of the MHT, spring-and-slider models with rate-weakening rheology are insufficient to explain die contrasted responses of die seismicity to the periodic loads that tides and monsoon both place on the MHT. Lnstead, we resort to numerical simulations using the Boundary Integral CYCLes of Earthquakes algorithm and examine die response of a 2D finite fault embedded with a rate-weakening patch to harmonie stress perturbations of varions periods. We show that such simulations are able to reproduce results consistent with a graduai amplification of sensitivity as die perturbing period get larger, up to a critical period corresponding to the characteristic Lime of evolution of the seismicity in response to a step-like perturbation of stress. This increase of sensitivity was not reproduced by simple 1D-spring-slider systems, probably because of the complexity of the nucleation process, reproduced only by 2D-fault models. When the nucleation zone is close to its critical unstable size, its growth becomes highly sensitive to any externat perturbations and the timings of produced events may therefore fmd themselves highly affected. A fully analytical framework has yet to be developed and further work is needed to fully describe the behavior of die fault in ternis of physical parameters, which will likely provide die keys to deduce constitutive properties of the MHT fion seismological observations
Soud, Ibrahim. "Modélisation en centrifugeuse pour l'étude du comportement d'un barrage en enrochement avec un noyau mince". Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27520.
Texto completoThis thesis contributes to the domain of geotechnical centrifuge modeling of rockfill dams. Given that odometer testing is usually used to estimate the vertical deformations of the central part of rockfill dams, a comparative study was performed between the vertical deformations of centrifuge models of rock particle assemblages with unsupported slopes (2D) and the vertical deformations observed during oedometer tests (1D). Both types of testing were conducted on rock particle assemblages with the same gradation while considering the effect of compactness. The comparison showed that for a given relative density, the centrifuge models experienced higher vertical deformations than those of the oedometer specimens and the ratio between the vertical deformation of the top of the models and that obtained during the oedometer tests decreases as relative density increases. Furthermore, another series of centrifuge tests was conducted on models of rockfill dams with thin central cores to simulate the typical behavior of such type of dams during construction and reservoir impoundment while exploring the effects of gradation and size scale on the response of these models. These models have different gradations while they have the same relative density. Throughout the tests, the response stiffness was higher as uniformity coefficient of the models’ gradations increases for the same maximum particle size and as maximum particle size decreases for parallel gradations. Particle size in large rockfill structures such as rockfill dams prevent laboratory testing of these materials and consequently, the prediction of field behaviour requires the development of an analysis method in order to extrapolate the laboratory testing results while taking the effects of size scale and gradation in consideration. An analysis method is adopted in this work in order to extrapolate the results of the centrifuge tests conducted on the already mentioned models of rockfill dams with central thin cores, which allowed the prediction of vertical deformations of different zones of the Romaine 2 dam. This analysis method is based on size scale effects on the crushability of granular materials and it considers past experimental findings relating to this issue. The predicted values of vertical deformations of different zones of the Romaine 2 dam were in the same order of the field measurement values during construction and reservoir impoundment.
Sossou, Agbéko. "Contribution à la réalisation d'un logiciel de simulation numérique pour la modélisation des déformations d'objets par la méthode des éléments finis". Aix-Marseille 3, 1990. http://www.theses.fr/1990AIX30055.
Texto completoLestriez, Philippe. "Modélisation numérique du couplage thermo-mécanique-endommagement en transformations finies : application à la mise en forme". Phd thesis, Université de Technologie de Troyes, 2003. http://tel.archives-ouvertes.fr/tel-00005309.
Texto completoZeng, Fanfei. "Contribution à la modélisation du comportement mécanique en grandes déformations élastoplastiques de films plastiques d’emballage". Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10109.
Texto completoShrink wrap films are composed of semi-crystalline polymers, possibly combined in multi-layers in order to benefit from the advantages of each of them. This work deals with the modeling of the mechanical behavior (under heat) of such materials in order to predict the improvement of their mechanical capabilities with uniaxial or biaxial drawing. From micro-structural observations and experimental results in uniaxial and biaxial stretching, an original model including three phases (which differ by the average distance between crystalline blocks) is developed for the prediction of the behavior of these films under various solicitations in finite elastoplasticity. In addition to the “crystalline” phase and the “amorphous” phase represented by a standard elastoplastic constitutive law and the classical 8-chain model, respectively, the intermediate phase allows one to take into account the effect of entanglements in the material and to explain the main differences, experimentally observed, between the uniaxial and biaxial behaviors.The model is calibrated from uniaxial tests in the case of PA6 and PE, and then validated for these two materials as well as multi-layer films for the uniaxial and equi-biaxial behaviors. The model is implemented in a finite element software in order to perform structural applications, such as the open hole test and the crack propagation, and validate again the efficiency of our 3-phase model
Coste, Christian. "Contribution à la simulation numérique du procédé d'extrusion-soufflage des réservoirs à carburants". Compiègne, 1997. http://www.theses.fr/1997COMP1000.
Texto completoNguyen, van Thien an. "Sur la modélisation et la simulation du couplage thermo-chimio-mécanique au sein des élastomères chargés". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4787/document.
Texto completoIn this prospective study, we propose a new thermo-chemo-mechanical coupled model for dissipative filled rubber. This work is based on experimental observations and results from the literature. In this context, we have developed three phenomenological constitutive laws within a generic thermodynamical framework. The models enters the category of the thermodynamics of irreversible processes. Intermediate states are taken into account in the model which is build within the generalized standard materials framework. The degree of cure is introduced as an internal variable. The evolution of this variable takes into account the thermal influence and the mechanical influence via the hydrostatic pressure. This is one of the features making this model original. A finite strains approach is considered. A finite element model is applied to the global problem. A monolithic solution scheme is built based on an implicit Euler scheme associated to a of Newton-Raphson linearization technique. This scheme takes into account the weak compressibility of the material condition through, first, a judicious choice of weak relations between unknowns, and second, an adequate choice of approximations for the unknowns of problem to enforce the stability of the numerical scheme. An object-oriented model for the constitutive equations of the thermo-chemo-mechanical model is proposed and is implemented in Java into the FEMJava code. Some simulations illustrate the high potential of these models in qualitatively reproducing these experimental observations
Sornin, Denis. "Sur les formulations élastoplastiques non locales en gradient d'endommagement". Troyes, 2007. http://www.theses.fr/2007TROY0011.
Texto completoFEM results of softening materials are well known to show pathological mesh dependency. The main goal of the present work, studying different types of formulation, is to give some elements to choose the better models able to avoid mesh sensitivity. A general study of the different sources of mesh and time dependency is carried out, and some existing solutions are presented. The case of elastoplastic damaging models with destination to industrial applications is specifically studied in the rest of the thesis. Formulations are presented and studied for a simple tension test, with various spatial discretisation. Numerical aspects and implementation in ABAQUS-standard environment is discussed. A new non local element is used for some of the formulations. The structure and details of this element are presented. For a given set of meshes, the ability of each formulation presented to control the size of the necking zone is studied. In the same time the independence of the global dissipation to the mesh size is checked. Practical and theoretical limits are highlighted. This study, gives some scientific and practical elements for the choice of a non local elastoplastic damaging model able to avoid discretisation sensitivity. For the end, the principal conclusions and the better developments in prospect are given
Mrani, Ibrahim. "Transport de matière en milieu biconstituant élastique : application au séchage du gel d'Agar". Montpellier 2, 1993. http://www.theses.fr/1993MON20040.
Texto completoBen, Salah Fatma. "Modélisation et simulation à base de règles pour la simulation physique". Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2293.
Texto completoThe physical simulation of deformable objects is at the core of several computer graphics applications. In this context, we are interested in the creation of a framework, that combines a topological model, namely Generalized Maps, with one or several mechanical models, for the physical animation of deformable meshed objects that can undergo topological modifications such as tearing or fractures.To obtain a general framework, we chose to rely on graph manipulation and transformation rules, proposed by the JERBOA software. This environment provided us with fast prototyping facilities for different mechanical models. It allowed us to precisely define how to store mechanical properties in the topological description of a mesh and simulate its deformation in a topologically-based manner for interaction computation and force distribution. All mechanical properties are stored in the topological model without any external structure.This framework is general. It allows for the simulation of 2D or 3D objects, with different types of meshes, including non homogeneous ones. It also allowed for the simulation of several, continuous or discrete, mechanical models with various properties of homogeneity and isotropy. Furthermore, different methods to simulate topological modifications have been implemented in the framework. They include both the selection of a criterion to trigger topological modifications and a transformation type. Our approach also managed to reduce the number of updates of the mechanical model after tearing / fracture
Rachik, Mohamed. "Simulation de la mise en forme des structures minces : soufflage des plastiques et emboutissage des tôles". Compiègne, 1993. http://www.theses.fr/1993COMP572S.
Texto completoAsad, Muhammad. "Elaboration of concepts and methodologies to study peripheral down-cut miling process from macro-to-micro scales". Lyon, INSA, 2010. http://theses.insa-lyon.fr/publication/2010ISAL0058/these.pdf.
Texto completoAujourd’hui, la méthode des éléments finis est suffisamment développée pour apporter aux ingénieurs, une aide indispensable lors des étapes de conception et d’optimisation des produits manufacturés. Dans certains cas, cette aide dépasse la simple assistance technologique et permet de considérer des lois physiques dans l’intimité d’un milieu inaccessible aux expériences (fission et fusion nucléaire, propagation des fissures dans les matériaux,…). C’est dans ce contexte à la fois scientifique et technologique que porte notre contribution sur la formation du copeau. D’un point de vue applicatif et expérimental, notre étude est centrée sur l’usinage de l’alliage d’Aluminium A2024-T351. Cette étude a été accomplie avec 4 étapes principales. La première étape porte sur la mise au point d’un modèle numérique 2D, de coupe orthogonale en tournage. Ce travail permet de choisir des solutions de détails pour ce modèle numérique, aussi bien au niveau de la discrétisation et de la partition du maillage qu’au niveau du comportement du matériau usiné sur les aspects cruciaux d’endommagement et d’énergie de rupture. Lors de la deuxième étape ce modèle a été adapté au cas du fraisage de profil en avalant avec un angle d’hélice nul, où la matière susceptible d’être enlevée a une forme en demi lune, constant sur sa largeur, présente une épaisseur continûment variable et tendant vers zéro. Ce travail et les résultats obtenus permettent de distinguer la zone de coupe macroscopique de la zone microscopique à partir de l’épaisseur coupée. L’effet de taille bien connu en micromécanique a ainsi été retrouvé lors de ce passage macro-micro à travers l’influence de l’écrouissage due à la vitesse de déformation du matériau. Le phénomène bien connu expérimentalement de l’augmentation quasi exponentielle de l’énergie spécifique de coupe avec la diminution de l’épaisseur coupée a été étudié en relation avec les divers aspects de cet effet de taille. Pour faciliter l’exploitation et proposer un outil de compréhension physique de l’enlèvement de matière à la communauté scientifique et à l’industrie, dans une troisième étape, le modèle de comportement de « Johnson-Cook » modifié par une approche basée sur le second gradient de déformation a été développé dans ABAQUS®/EXPLICIT sous la forme d’un sous programme (ou sous-routine VUMAT). Finalement, au cours de la quatrième étape, l’application a été complètement développée pour simuler le fraisage de profil en avalant, de l’alliage d’Aluminium A2024-T351. En plus de l’effet de taille interne au copeau, les aspects dynamiques liés au comportement du système usinant ont été pris en compte à travers un modèle multi-échelle nommé « modèle dynamique hybride de coupe (HDC-modèle) » qui combine la rigidité équivalente d'une fraiseuse à grande vitesse (outil, porte-outil, broche, …) au niveau macroscopique avec la mécanique de formation de copeau au niveau mésoscopique. Cette application intégrant à la fois les effets d’échelles a pour but de fournir des données numériques sur la surface usinée qui puissent être comparées à des résultats expérimentaux. Malgré les difficultés de modélisation nous avons tenu à élaborer ce modèle complet car c’est bien la partie microscopique de la coupe en dynamique haute fréquence ou grande vitesse qui génère la surface usinée. Pour finir, des coupes expérimentales ont été exécutées en tournage et en fraisage pour valider les modèles proposés. Les résultats numériques sont ainsi comparés à ceux expérimentaux à chacune des étapes. De manière générale la concordance des résultats est bonne. Il faut cependant noter le grand nombre de paramètres des modèles numériques qui certains d’entre eux peuvent être des paramètres de recalage expérimental. Il apparaît donc que le caractère prédictif du modèle est limité essentiellement par les caractéristiques physiques de la matière usinée. On se retrouve dans la situation purement expérimentale des années 1970-80 qui a vu naître la notion de couple outil-matière (COM). L’approche d’aujourd’hui, à la fois expérimentale et numérique permet cependant de réduire fortement les coûts et de quantifier des phénomènes locaux très intéressants comme par exemple dans notre contribution : La propension à la segmentation et donc à la fragmentation dans certaines conditions de coupe, La longueur du contact copeau, face de coupe, l’amplitude des défauts de la surface usinée due à la dynamique globale
Ziane, Mustapha. "Contribution à la simulation numérique du soufflage-thermoformage de corps creux plastiques axisymétriques". Compiègne, 1999. http://www.theses.fr/1999COMP1252.
Texto completoAli, Bassem. "Modèle numérique pour comportement mécanique des chaussées : application à l'analyse de l'orniérage". Lille 1, 2006. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2006/50376-2006-Ali.pdf.
Texto completoJoste, Baptiste. "Simulation of plastic strain localization by Discrete Dislocation Dynamics and crystal plasticity". Electronic Thesis or Diss., Université Paris sciences et lettres, 2023. http://www.theses.fr/2023UPSLM077.
Texto completoUnderstanding the deformation processes leading to the failure of polycrystalline materials is one of the major challenges in materials science. To date, the mechanisms of plastic strain localization into slip bands and the propagation of deformation through a polycrystalline aggregate are not fully understood. Investigating such phenomena is the aim of the 3DiPolyPlast ANR project. In the proposed multi-scale simulation approach, Discrete Dislocation Dynamics (DDD) simulations will be used to better model the individual and collective behavior of dislocations at the mesoscopic scale. The majority of the simulations carried out are based on a so-called weak coupling between DDD and the Finite Element Method (FEM), in which the stress field resulting from a FEM calculation in elasticity is used as the initial intragranular loading condition. This assumption enables a more systematic and physically justified study of the various mechanisms taking place during plastic deformation within the dislocation microstructure. The simulations carried out show the role played by the polycrystalline microstructure on the localization of plastic deformation, notably through elastic deformation incompatibilities leading to the appearance of intragranular stress concentrations. Using these simulations, we show that during plastic deformation, certain mechanisms such as cross-slip or collinear annihilation allow plastic deformation to initiate in certain regions of the grain. Meticulous observation of this dislocation microstructure has enabled us to reconsider one of the initial assumptions of our DDD simulations, the impenetrability of grain boundaries. In fact, the number of dislocations stacking up at grain boundaries is significant, and the stresses calculated at the head of these stacks are of the order of the GPa. Part of the work presented in this manuscript has therefore been dedicated to the implementation of a local rule to model the reaction mechanisms between dislocations and grain boundaries during plastic deformation. In addition, we have shown that these reaction mechanisms are responsible for a sharp decrease in kinematic strain hardening, leading to intense plastic slip in local regions of the grain. Further calculations were carried out within the framework of the discrete-continuous model (DCM), which couples crystal plasticity finite element calculations carried out on the complete polycrystalline aggregate with DDD simulations. This modeling provides a more precise description of plastic deformation mechanisms, and represents a major asset in the study of the role of interactions between grains, particularly during their plastic deformation. These simulations are also proving to be a source of information for better understanding the diffraction contrasts observed experimentally in X-ray topo-tomography
Leszczynski, Aleksander. "Modélisation de l'arthrodèse thoraco-lombaire avec fixation pelvienne dans les déformations du rachis". Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAD041.
Texto completoDegenerative scoliosis and sagittal imbalance are common problems in the older population. In order to improve the quality of life, some patients are recommended to undergo surgical correction. Surgical correction of the sagittal balance can lead to various complications, including rod fractures, which play a central role in the long term. Patient follow-up studies have shown that a rupture of the osteosynthesis material is observed in about 20% of patients. The main focus of the curent work was the development of a complete finite element model (FEM) of the healthy spine. The geometry of the FEM was based on a CT-scan of a healthy 47-year-old volunteer. Mechanical properties were taken from a wide literature review and implemented. In order to ensure the biofidelity, the spinal FEM was widely validated in terms of range of motion (ROM) and modal analysis against multiple experimental studies from the literature. For the study of osteosynthesis material, four instrumented FEMs of the lumbar spine with different configurations were proposed. For the first time, a validation was performed on instrumented flexible spine FEMs against ROM as well as strains in the main rods. In addition, other mechanical parameters such as intradiscale pressure, forces in the screw heads and the distribution of Von Mises stresses in the main rods were calculated to evaluate the studied instrumented configurations. Outcome of the present study of the four instrumented lumbar FEMs in four loading modes (extension flexion, lateral inflection and torsion) indicated that the maximum Von Mises stress (located in the main rods) is correlated with the area of rod fractures reported in patient follow up studies. However, the bi-lateral double rod configuration with interbody cages produced the higher Von Mises stress reduction on spinal fixators which represents a minimal risk of rod failure. A complementary study was also carried out to investigate the FEM of an instrumented spine from T10 to the pelvis. The results showed that an extension of the instrumentation thoracic part, the numerically obtained values were more critical than during an instrumentation of the lumbar part alone, especially in terms of maximum stresses calculated in the principal rods. The developed spinal FEM can be an effective and efficient tool to evaluate other surgical instrumentation techniques using the finite element method
Bernard, Chrystelle. "Intégration dans un code éléments finis d'un modèle de comportement en grandes déformations pour les polymères amorphes : applications à une large gamme de vitesses de déformation et à la mise en forme". Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAD018/document.
Texto completoNowadays, numerous structural parts are made in polymeric materials. These materials exhibit a complex behavior strongly sensitive to strain rate and temperature. Numerous constitutive equations have been developed during the last decades in order to describe the elastic-viscoplastic behavior of polymers in finite strain for a wide range of strain rates and temperature. To provide for the holding of mechanical parts polymer subject to a complex set of loads, the use of numerical methods, such as Finite Element (FE) method, is unavoidable. However, the quality of the numerical prediction is strongly dependent to the used constitutive equations. Thus, we proposed to study two models of mechanical behavior implemented in two FE softwares: a simple phenomenological model, introduced in CAST3M, and a micromechanical model, introduced in ABAQUS/Explicit. The phenomenological model allows simulating the mechanical behavior of glassy polymers in small strains over a reduced range of strain rates and temperatures. A compressive test reproducing the Split Hopkinson Pressure Bar device is simulated for several strain rates and temperatures. A good correlation is found between experimental results and numerical predictions. Moreover, an estimation of Taylor-Quinney coefficient and the interfacial stress, due to the friction between the polymer sample and the compressive bars, have been found. The micromechanical model describes the mechanical behavior of amorphous polymers in finite strain over a wide range of strain rates and temperatures. It has been developed in our research team by Richeton et al. [Int. J. Solids Struct. 44 (2007) 7938] and proposes to take into account the strain rate and temperature dependence of various material properties (elastic modulus, yield stress, orientational hardening). In order to simulate the mechanical behaviour of polymeric structures under dynamic loadings or during forming processes, a VUMAT subroutine is written. After validation of the numerical implementation of the VUMAT subroutine for simple compressive/tensile tests, two applications were simulated. The first application is a normal impact test of a polymeric plate by a hemispherical projectile. The second application is a cold forging test. In both cases, numerical predictions are in agreement with the experimental results from the literature
Taro, Mandikizinoyou. "Modélisation et simulation des procédés de mise en compression des surfaces à très grandes vitesses de déformation par méthode semi-analytique". Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0105/document.
Texto completoThe failure of the mechanical parts is very often initiated by a surface defects. Consequently, the generation of compressive residual stresses on mechanical parts by introducing a heterogeneous plastic strain improves the resistance to fatigue and increases the lifetime of the parts. Among the processes making it possible to introduce residual stresses into the parts, the laser shock peening is more interesting for several reasons. On the one hand, it makes it possible to produce pressures on the surface of material of about 1 to 6 going GPa over short pulse times from 3 to 30 nanoseconds. In addition, he gives the opportunity of introducing residual stresses of compression on a certain depth while preserving the initial state of the treated part. The numerical simulation becomes necessary to determine the best physical phenomena involved. Thus, the semi-analytical method offers a lot of advantages, in particular the simplicity of the models and the computation times saving. This method was never extended to the dynamic problems. In this thesis the semi-analytical method was extended to the dynamic problems and the model implemented is applied for the simulation of the Laser process of shock
Trombini, Marion. "Couplage endommagement-grandes déformations dans une modélisation multi-échelle pour composites particulaires fortement chargés". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2015. http://www.theses.fr/2015ESMA0002/document.
Texto completoThis study is devoted to multi-scale modeling of highly-filled particulate composites.This method, the “Morphological Approach” (M.A.), is based on a geometrical and kinematicalschematization which allows the access to both local fields and homogenized response. In order toevaluate the predictive capacities of the M.A. considering a linear elastic behavior for the constituentsand evolution of damage, analysis is performed regarding the ability of the M.A. to accountfor particle size and interaction effects on debonding chronology. For that purpose, simple periodic,random monomodal and bimodal microstructures are considered. The results are consistent withliterature data : debonding of large particles occurs before the one of smaller particles and thehigher the particle volume fraction, the sooner the debonding. Finally, the objective is to operatethe coupling of two non linearities which were separately studied in previous versions of the M.A. :debonding between particles and matrix, and finite strains. The whole analytical background of theapproach is reconsidered in order to define the localization-homogenization problem. The nucleationcriterion is extended to the finite strains context. The final problem, strongly non linear, is numericallysolved through a Newton-Raphson algorithm. The different solving steps (jacobian matrix,coding with Python®) are developed. Progressive evaluations (sound and damage materials) allowthe validation of numerical implementation. Then, size and interaction effects are reproduced infinite strains
Bilger, Alexandre. "Patient-specific biomechanical simulation for deep brain stimulation". Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10136/document.
Texto completoDeep brain stimulation is a neurosurgical treatment involving the permanent implantation of electrodes in the brain, to stimulate a specific deep structure. Electrical stimulation of some brain structures treat symptoms of motor or affective neurological disorders. The success of the operation relies on the electrode placement precision, which the goal is to maximize the therapeutic outcomes, and minimize the adverse effects. To do that, a pre-operative planning step determine the target coordinates to stimulate, as well as the electrode trajectory to reach it, thanks to a combination of medical images of the patient and numerical tools. However, intra-operative brain deformation, called brain shift, might invalidate the planning. The contributions of this thesis rely on a biomechanical model of brain shift which comprises a mechanical model for deformation, as well as a model of cephalo-spinal fluid leak. We present a pre-operative tool, based on our model, in order to provide to the surgeon an information on the deformation risks, that he could use to select a safe trajectory for the patient, even in the case of brain shift. Moreover, we propose a intra-operative registration method based on our biomechanical model, in order to compute the new location of anatomical structures. Finally, thanks to a model of insertion of the electrode and its interaction with brain tissue, we reproduce the operating protocol in order to compute the electrode curvature due to brain shift
Haouchine, Nazim. "Image-guided simulation for augmented reality during hepatic surgery". Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10009/document.
Texto completoThe main objective of this thesis is to provide surgeons with tools for pre and intra-operative decision support during minimally invasive hepatic surgery. These interventions are usually based on laparoscopic techniques or, more recently, flexible endoscopy. During such operations, the surgeon tries to remove a significant number of liver tumors while preserving the functional role of the liver. This involves defining an optimal hepatectomy, i.e. ensuring that the volume of post-operative liver is at least at 55% of the original liver and the preserving at hepatic vasculature. Although intervention planning can now be considered on the basis of preoperative patient-specific, significant movements of the liver and its deformations during surgery data make this very difficult to use planning in practice. The work proposed in this thesis aims to provide augmented reality tools to be used in intra-operative conditions in order to visualize the position of tumors and hepatic vascular networks at any time
Promma, Nattawit. "Méthode des champs virtuels en grandes déformations : application à la caractérisation d'un matériau élastomère à partir de mesures de champs cinématiques". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2009. http://tel.archives-ouvertes.fr/tel-00725718.
Texto completoPromma, Nattawit. "Méthode des champs virtuels en grandes déformations : application à la caractérisation d'un matériau élastomère à partir de mesures de champs cinématiques". Phd thesis, Clermont-Ferrand 2, 2009. http://www.theses.fr/2009CLF21920.
Texto completoKaszinski, Patrick. "Indentation cyclique et déformation progressive : étude expérimentale et simulation des contacts internes à des implants chirurgicaux". Cachan, Ecole normale supérieure, 1999. http://www.theses.fr/1999DENS0012.
Texto completoRaid, Idir. "Développement de méthodes numériques et de caractérisations expérimentales pour l’étude des contraintes mécaniques et défaillances induites dans les dispositifs microélectroniques avancés". Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALI084.
Texto completoThe trend in the microelectronics industry is towards miniaturisation, from transistors to the integrated circuit package. This constant desire of compactness is certainly motivated by economic reasons, but also by the perspectives to gain in performance, power and ergonomics. In early 90s, 0.8 µm was the transistors gate length at major semiconductor manufacturers. The length has been reduced to 6 nm with a density of integration of 125 million transistors per square millimetre. However, such a transition does not come without consequences, as far as it concerns fracture mechanisms, it is particularly true regarding the low-k dielectrics. This family of materials, although porous and fragile, is essential to ensure the insulation in the circuitry of an increasingly dense Back-End of Line (BEoL), with increasingly fine lithography. Besides, due to its porosity, it also has a hydrophilic behaviour which greatly reduces both its insulation quality and stress strength. For all these reasons, the seal ring, the copper interconnection structure that encircles the chip, was implemented to (i) ensure the mechanical integrity of its interior, containing the electrically active part of the die, and (ii) to protect it from moisture and other chemicals intrusions. Hence the interest of this work to address the thermomechanical stresses and cracking phenomena which are articulated around the BEoL. To do so, various paths revolving around the same line of research, mechanical integrity in microelectronics systems, are proposed. (i) Two ways of evaluating stress fields in active silicon and passive BEoL are investigated: by implementing sensor structures based on the principles of piezoresistance and extensometry respectively. (ii) The Four-Point Bending technique is benchmarked, and readapted to account for the crack length, for cracks advancing is homogeneous (decohesion) and heterogeneous (debonding) thin films structures. (iii) A Finite Elements approach, combined with Cohesive Zone Models under Small-Scale Yielding conditions, is proposed to analyse the influence of the arrangement and plasticity of copper in the interconnections in the resistance to crack advance
Charvet, Quemin Françoise. "Synthèse modale des systèmes articulés en grands déplacements". Paris 6, 1990. http://www.theses.fr/1990PA066076.
Texto completoPierson, Gaël. "Interaction implant – os élastique micropolaire : une investigation numérique". Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0054.
Texto completoThe repair of the human is a sector of activity which requires skills in medical sciences and sciences known as "hard". In many cases, all or part of an organ must be replaced by a substitute made of inert material. This is for example the case in implantology where one is interested in the replacement of teeth. The installation of a dental implant is a surgical act which consists in introducing into the bone of the mandible a device made of inert material intended to receive the dental crown. These prostheses are more or less tolerated by the living organism (about 5% of rejection) and can in some cases lead to a bone ruin or cause infections known as peri-implantitis. To improve the biocompatibility of these medical devices, several tracks are explored. We can focus on the geometry of the implant and its surface condition, the material of the implant or the mechanical bone / implant system. It is in this last frame that we located our work of thesis. The bone / tooth system is a mechanical system subject to repeated intense stress. The levels of stress and deformation achieved during chewing contribute to the overall stability and viability of these living media. These stress and strain levels must be reproduced in the bone in the case of the bone / implant system. It is hoped to ensure the viability of the bone and to avoid the various processes of degradation. It is therefore necessary to simulate and analyze the response of such a system to mechanical stresses. This work requires modeling the behavior of the bone and the implant. The latter is considered as a conventional metallic material stressed in its field of elastic deformation. As for the bone, its fine observation reveals its multi-scale nature and we have chosen to model its behavior by a particularization of Eringen's micromorphic environment. More precisely we have considered it as a micropolar elastic medium. To solve the field equations of the problem, it was necessary to develop a dedicated digital tool. This tool is based on a clever combination of the boundary element method and a meshless method, more precisely a collocation method. At first, in order to understand the principle of the method, we developed the numerical tool to solve a scalar field equation, here equation of transient thermal conduction. We have seen the effectiveness of the method for three-dimensional systems. In a second time we adapted our numerical method to solve vector field equations which are in our case the equations for the micropolar elastic media. The digital tool has been validated on a number of examples having an analytical solution or in comparison with the results of the literature. The digital tool was then applied to the analysis of the bone / implant system. To understand the contribution of the microstructure of a micropolar elastic medium, compared to a conventional elastic medium, we made different studies of the implant / bone system under various mechanical stress considering both types of modeling for the bone. The macroscopic parameters for a micropolar elastic medium are the same as for a conventional elastic medium. The differences obtained will come only from the contribution of the microstructure. The results obtained show that the fine modeling of the mechanical behavior adopted for the bone is realistic with regard to the stresses induced by the stress and to the noticeable decrease of the stress jumps at the bone / metal interface compared to the case of the modeling of the equivalent classic elastic medium. These results have already made it possible to understand certain clinical observations
Limouni, Achour. "Étude dynamique, théorique et expérimentale des essais de frottement pion-disque". Compiègne, 1998. http://www.theses.fr/1998COMP1106.
Texto completoDereims, Arnaud. "simulation industrielle des procédés d’élaboration de pièces composites par infusion de résine : couplage fluide / solide poreux très faiblement perméable en grandes déformations". Thesis, Saint-Etienne, EMSE, 2013. http://www.theses.fr/2013EMSE0699/document.
Texto completoComposite manufacturing processes by resin infusion, despite their many benefits, struggle to establish themselves in the industrial production phases due to difficulties to control them. So, in partnership with ESI Group, a comprehensive model for the simulation of these processes is developed at the ENSM-SE since the pioneering work of P. Celle.Our work focuses on the generalization of this model to handle complex industrial cases in three dimensions, as well as its extension to “post-infusion” flow simulation. The approach is based on three domains decomposition of the field (Distribution medium, impregnated preforms, dry preforms) consisting in coupling a Stokes flow in the distribution medium with a Darcy flow in the preforms. In addition, the mutual influence of the resin on the preforms and of the preforms deformation on the permeability is considered, through Terzaghi’s law and models expressing the permeability as a function of the fibre fraction, data only accessible with a 3D coupled mechanical approach. Finally, the process is divided into three phases: initial compression of dry preforms, filling and “post-infusion”. The numerical methods developed in this work, apply to real infusion cases often discarded in recent publications, involving very low permeability (~10-15 m²), thin distribution medium (~ 1 mm) and complex geometries (3D curved).This innovative approach has been implemented in an industrial simulation code (ProFlotTM), validated analytically over test cases and experimentally over industrial cases in the European project INFUCOMP
Meissonnier, Franck. "Couplages thermomécaniques et homogénéisation". Montpellier 2, 1996. http://www.theses.fr/1996MON20263.
Texto completoHuang, Qun. "Multi-scale modeling and simulation on buckling and wrinkling phenomena". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0033/document.
Texto completoThe main aim of this thesis is to develop advanced and efficient multi-scale modeling and simulation techniques to study instability phenomena in three common engineering structures, i.e., membrane, film/substrate and sandwich structures, by combining the Technique of Slowly Variable Fourier Coefficients (TSVFC) and the Asymptotic Numerical Method (ANM). Towards this end, based on the Von Karman plate equations, the TSVFC has been firstly used to develop a two-dimensional (2D) Fourier double-scale model for membrane, which has also been implemented into ABAQUS via its subroutine UEL. Then a 2D Fourier model is constructed for film/substrate. Further, making use of deformation features of the film/substrate, a 1D Fourier model is developed by using both the TSVFC and the Carrera’s Unified Formulation (CUF). Subsequently, based on high-order kinematics belonging to Zig-Zag theory, a 2D Fourier model is deduced for sandwich plate. The governing equations for the above models are discretized by the Finite Element Method, and the resulting nonlinear systems are solved by the efficient and robust nonlinear solver ANM. These models are then adopted to study instabilities in these structures. Results show that the established models could accurately and efficiently simulate various instability phenomena. Besides, it’s found that the membrane instability is very sensitive to boundary conditions, and there exists a dimensionless parameter that is almost constant near bifurcation point for various loading cases and geometric parameters, which may be helpful for fast predicting the occurrence of wrinkles
Ben, Elhaj Salah Sami. "Modélisation non-locale et stochastique de matériaux à fort gradient de propriétés par développement asymptotique". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2019. http://www.theses.fr/2019ESMA0018.
Texto completoThe aim is to propose a macroscopic, deterministic and non-local model, constructed by scale transition for heterogeneous materials with high property gradients and containing a random distribution of inclusions. More precisely, the inclusions are distributed in an elastic matrix according to a stochastic ergodic process. Several non-local models exist in the literature, but they do not allow (or very little) to obtain non-local quantities and/or fields at the macroscopic scale from a scale-transition. Besides, it is often difficult to link the non-local parameters to the microstructure. To this aim, we developed a two-step approach.In the first stage, we combined the method of asymptotic developments with an energetic approach to reveal a second displacement gradient in the strain energy. The advanced model involves three homogenized elasticity tensors functions of the stochastic parameter and of the phase properties. As opposed to the literature, the model involves two characteristic lengths strongly linked to the microstructure. These lengths define two morphological representative elementary volumes on which full field simulations are performed in order to determine the macroscopic strain tensors at orders 0 and 1 involved in the formulation of the model. In order to test this first version of the model, numerical simulations were performed. The estimate of the classical part of the energy, coming from the local part of the fields, has been successfully compared to classical bounds for a composite bar consisting of a random distribution of two homogeneous and isotropic elastic materials. Then, numerical solving of the whole model including the non-local terms has been performed in the three-dimensional case. Two types of microstructures with increasing morphological complexity were used. The first ones are virtual microstructures generated from a given simple pattern randomly distributed throughout the structure and composed of a big inclusion circled by six identical small ones. The second are real microstructures of Ethylène-Propylène-Diène Monomère (EPDM) obtained by tomography and containing clusters of inclusions with complex structures.In order to obtain a macroscopic model that can be used for structure analysis, without any full field intermediate calculations, a second scale transition has been performed using stochastic variational homogenization tools in the ergodic case. More precisely, the Γ-convergence method has been used in order to have a convergence of energy rather than that of mechanical fields, aiming at keeping a strong microstructural content. In fine, the model is macroscopic, non-local, deterministic and strongly connected to the microstructure. Non-local effects are now accounted for by the presence of the second displacement gradient but also by the presence of the virtual (memory) displacement field of the inclusions. The link with microstructure is still manifest through the presence of the stochastic parameter and phase properties, but also by the presence of the asymptotic fractions of the inclusion phase in the material and in each of the morphological volumes defined by the model characteristic lengths. In order to prepare the use of the model for structure calculations, a non-local finite element enriched with Hermit-type interpolations was implemented in FoXtroT, the finite element solver of the Pprime Institute. This element takes into account the virtual (memory) displacement field related to inclusions as well as the gradients of the macroscopic and virtual displacement fields. The first numerical results on this aspect, to our knowledge never discussed in the literature, are promising
Fleuret, Clément. "Approche multi-échelle pour la prédiction de la tenue d'une aile caisson dédiée à l'aviation légère : expérimentation et simulation". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2016. http://www.theses.fr/2016ESMA0013.
Texto completoAircraft wings are composed of a growing composite part portion. To reduce production and assembly certification costs, a new hollow box architecture is proposed with a one shot manufacturing process. This structure includes T-connections between honeycomb sandwich panels. Mechanical behavior and degradation modes are unknown for this structure. A multiscale methodology is developed to deepen the wing damage knowledge and to improve the numerical sizing tool.Firstly, specimen-testing couples are designed to represent the loading modes of the T-connections. A detailed analysis of instrumented testing allows to understand the damage scenarios for each mode. The first damage stages are mainly driven by the honeycomb behavior (shear, tear). A 3D numerical model represents the first damage stages. It is built with a shell representation of the honeycomb which integrates the structure variability (bonding, deformation of cells). An elastic-plastic damage law (unidirectional and woven plies) is developed for the wing materials. Then, it is implemented for multi material laminate. Based on this model, a simplified modeling is realized for the connection behavior. It consists of assembling shells by connectors with elastic-plastic properties. Building a predictive wing simulation requires a simplified model integration of the T-bond behavior
Cao, Hua Lei. "Modélisation mécanique et simulation numérique de l'emboutissage : application à la déformation plane et axisymétrique". Grenoble INPG, 1990. http://www.theses.fr/1990INPG0043.
Texto completoYang, Fangtao. "Simulation of continuous damage and fracture in metal-forming processes with 3D mesh adaptive methodology". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2385/document.
Texto completoThis work is part of the research carried out in the framework of a collaboration between the Roberval laboratory of the Compiègne University of Technology and the team within the framework of the project ANR-14-CE07-0035 LASMIS of the Charles Delaunay Institute of Technology University of Troyes. In this work, we present a three-dimensional adaptive Pi-methodology of finite elements to represent the initiation and propagation of cracks in ductile materials. An elastoplastic model coupled with the isotropic damage proposed by the LASMIS / UTT team is used. The targeted applications will mainly concern the metal forming. In this context, an updated Lagrangian formulation is used and frequent remeshing is essential in order to avoid the strong distortion of elements due to large plastic deformations and to follow the modifications of the topology resulting in the creation of cracks. The size of the new mesh must allow at a lower cost to accurately represent the evolution of the gradients of the physical quantities representative of the studied phenomena (plasticity, damage ...). We propose empirical indicators of size of elements based on the plastic deformation as well as on the damage. A piecewise defined curve represents the evolution of the element size according to the severity of the plasticity and, if appropriate, the damage. The cracks are represented by a method of destruction of elements which allows an easy description of the geometry and a simplified treatment of the cracking without any need for additional criteria. On the other hand, to allow a realistic description of the cracks, the latter must be represented by erosion smaller elements. An ABAQUS / Explicit@ solver is used with quadratic tetrahedral elements (C3DIOM), avoiding in particular the problems of numerical locking occurring during the analysis of structures in compressible or quasi-incompressible material. The control of the smaller mesh size is important in an explicit context. In addition, for softening phenomena, the solution depends on the mesh size considered as an intrinsic parameter. A study has shown that when the mesh is sufficiently refined, the effects of mesh dependence are reduced. In the literature, the costs of frequent meshing or remeshing are often considered prohibitive and many authors rely on this argument to introduce, with success, alternative methods that limit the cost of remeshing operations without eliminating them ( XFEM for example). Our work shows that the cost of local remeshing is negligible compared to the calculation. Given the complexity of the geometry and the need to refine the mesh, the only alternative to date is to use a mesh in tetrahedra. The strategy of local remeshing tetrahedron is based on a bisection method followed if necessary by a local optimization of the grid proposed by A. Rassineux in 2003. The remeshing, even local, must be accompanied by field transfer procedures on both nodal variables and integration points. Node variables are, as most authors do, transferred using finite element shape functions. The 3D field transfer at Gauss points and the many underlying problems have been relatively untouched in the literature. The main difficulties to be solved in order to ensure the "quality" of the transfer concern the limitation of numerical diffusion, the lack of information near borders, the respect of boundary conditions, the equilibrium, the calculation costs, the filtering of the information points, crucial problems in 3D where the number of Gauss points used is several hundred. We propose a so-called "hybrid" method which consists, initially, in extrapolating the data at the Gauss points, in the nodes by diffuse interpolation and then in using the finite element form functions to obtain the value at the point considered