Search results for "éléments finis"
showing 10 items of 10 documents
Original strain energy density functions for modeling of anisotropic soft biological tissue
2017
This thesis has focused on the construction of strain energy densities for describing the non-linear behavior of anisotropic materials such as biological soft tissues (ligaments, tendons, arterial walls, etc.) or fiber-reinforced rubbers. The densities we have proposed have been developed with the mathematical theory of invariant polynomials, particularly the Noether theorem and the Reynolds operator. Our work involved two types of anisotropic materials, the first with a single fiber family and the second with a four-fiber family. The concept of polyconvexity has also been studied because it is well known that it plays an important role for ensuring the existence of solutions. In the case o…
Te-As-Se glass microstructured optical fiber for the middle infrared
2009
International audience; We present the first fabrication, to the best of our knowledge, of chalcogenide microstructured optical fibers in Te-As-Se glass, their optical characterization, and numerical simulations in the middle infrared. In a first fiber, numerical simulations exhibit a single-mode behavior at 3.39 and 9.3 μm, in good agreement with experimental near-field captures at 9.3 μm. The second fiber is not monomode between 3.39 and 9.3 μm, but the fundamental losses are 9 dB/m at 3:39 μm and 6 dB/m at 9.3 μm. The experimental mode field diameters are compared to the theoretical ones with a good accordance.
Contribution to the investigation of dynamic responses of human tissues under high velocity impacts using finite element modeling
2022
Thoracic injuries happen frequently in various frameworks of high velocity impact biomechanics. Rib fractures and lung injuries are the most common hard and soft tissue injuries in human thorax. This thesis aims to contribute to the investigation of dynamic responses of human tissues especially ribs and soft tissues under high velocity impacts using finite element modeling. Firstly, a novel strain-rate-dependent elasto-hydrodynamic constitutive law of the synthetic polymer Styrene-Ethylene-Butylene-Styrene (SEBS) gel was proposed and implemented as a user material subroutine in Radioss (Altair Hyperworks) to interpret dynamic behaviors of SEBS gel under various loading configurations. Numer…
Prédiction de la contrainte de rupture de composites unidirectionnels et suivi de l'accumulation de ruptures de fibres
2005
Modeling and numerical simulation of the propagation of pitting corrosion of iron in chlorinated medium : contribution to the evaluation of the durab…
2012
This study deals with the understanding of the mechanisms of pitting corrosion susceptible to occur on carbon steel selected for high level nuclear waste containers. Transport/reaction models have been developed in order to simulate, by finite element method, the propagation of a pit on iron in chlorinated medium. For conservative models, pit is activated by imposing a potential on metal. Thanks to different parametric studies (geometry, environment…) simulations have permitted to classify, by severity order, the factors responsible of the increase or the inhibition of the localized corrosion rate. Otherwise, experiments on occluded (called « lead-in-pencil ») electrodes confirm that confin…
Modélisation de phénomènes locaux : vers leur prise en compte dans la simulation de la cinétique d'oxydation d'un métal.
2006
The oxidation of metals is a complex process involving several mechanisms that take place at different length scale (macroscopic and microscopic). In this work, we try to integrate local phenomena (microscopic scale) in macroscopic models, especially to the modelling of the metal oxidation kinetics. The study is divided in two parts ; the first one based on non-equilibrium thermodynamics allows us to obtain the evolution laws of the system metal/oxyde, those were used to modelling oxidation kinetics. The second one is microscopic ; it consists in a study of the thermo-mechanical behaviour of various aluminium surfaces by molecular dynamic and the calculation of their surface energy density.…
Study of fatigue behavior of plant fiber reinforced composites : taking into account the variability of properties
2012
The present study focuses on the characterization and comparison of the quasi-static and fatigue properties of flax and glass fibre reinforced composites with an epoxy matrix. An extensive experimental campaign of fatigue tests have been performed using the measured quasi-static tension and in plane-shear properties. It appears that the static and fatigue characteristics of the glass/epoxy composites are higher than that of flax/epoxy ones with similar fibre volume fraction and lay-ups. However, due to the low density of flax reinforcements, the differences between the specific properties of the two materials are low. The measurement of the evolution of the fatigue properties has highlighte…
Sur la prise en compte de quelques conditions aux limites avec la méthode des éléments finis
2017
Ce cours a pour principal sujet la discrétisation de certaines conditions limites sur le bord d'un domaine à l'aide de la méthode des éléments finis. Nous étudions en particulier des problèmes elliptiques avec conditions de Dirichlet non-homogènes, puis avec conditions de Signorini. Les conditions de Signorini sont des conditions de contact unilatéral entre un solide et un support rigide. Différentes méthodes sont passées en revue, et nous détaillons l'analyse pour les méthodes classiques et celle de Nitsche.
HHT-alpha and predictor-corrector scheme for dynamic contact problem by Nitsche's method
2022
Dans ce travail nous sommes intéressés par le problème de contact unilatéral en dynamique et sans frottement. Nous nous concentrons sur l'évolution en temps de l'impact d'un corps élastique linéaire sur un obstacle rigide, et avons souhaité en particulier étudier comment combiner des schémas en temps comme HHT et prédicteur-correcteur avec un traitement du contact via Nitsche, ce qui n'a jamais été effectué auparavant. Nous présenterons aussi quelques résultats numériques en faisant attention au comportement numérique : stabilité du schéma, conservation ou non de l'énergie et oscillations parasites. Mots clés-problème de contact, méthode de Nitsche, éléments finis, dynamique.
Contribution to the modeling of microstructural corrosion on aluminium alloys : definition of a methodology to study the bimetallic corrosion phenome…
2008
The initiation and the propagation of aluminum alloys microstructural corrosion is mainly based on the bimetallic corrosion phenomenon. This type of corrosion is caused by galvanic coupling at a local scale between the different phases contained in the alloy. The description of the localized corrosion phenomenon has been largely studied. Their complexity can explain why they are so difficult to predict by the way of numerical tools and why the works that have been done on this subject are so scarce. The present thesis brings a new contribution to this field by suggesting a methodology based on the complementary use of local electrochemical techniques and the finite element simulation of bim…