In order to investigate the thermal stress and expansion as well as the associated strain effect on material properties caused by high temperature and large temperature gradient, a two-way thermo-mechanical coupling solver is developed. This solver integrates a new structural response module to the Kentucky Aerothermodynamics and Thermal response System (KATS) framework. The structural solver uses a finite volume approach to solve either hyperbolic equations for transient solid mechanics, or elliptic equations for static solid mechanics. Then, based on the same framework, a quasi-static approach is used to couple the structural response and thermal response to estimate the thermal expansion and stress within Thermal Protection System (TPS) materials. To better capture the thermal expansion and study its impacts on material properties such as conductivity and porosity, a moving mesh scheme is also developed and incorporated into the solver. Grid deformation is transferred among different modules in the form of variations of geometric parameters and strain effects. By doing so, a bi-direction information loop is formed to accomplish the two-way strong thermo-mechanical coupling. Results revealed that the thermal stress experienced during atmospheric re-entry concentrates in a banded area at the edge of the pyrolysis zone and its magnitude can be large enough to cause the failure of the TPS. In addition, thermal expansion causes the whole structure to deform and the changes in material properties. Results also indicated that the impacts coming from structural response should not be ignored in thermal response.

¡@¡@Wire bonding has been used in integrated circuit packaging for many years which has been more full-grown than other bonding methods, and gold wire has been the preferred choice. Because of the rising price of gold every year, copper wire has been increasingly used to replace gold wire. ¡@¡@The main focus of this paper is to simulate 3D copper-Al pad thermosonic wire bonding stage by using 3D finite element method. Firstly, the differences between mechanical analysis (the thermal effect was not considered) and thermo-mechanical coupling analysis from both impact stage and ultrasonic vibration stage, respectively, were compared. Secondly, the differences between copper thermosonic wire bonding analysis and gold thermosonic wire bonding analysis were discussed. Finally, the effects of Al pad thickness variation on the copper thermosonic wire bonding analysis were studied. ¡@¡@Results showed that, due to the mechanical properties will be decreased by thermal effects caused from temperature increasing, the obtained effective stress and efective strain of thermo-mechanical coupling analysis were less than the results obtained from mechanical analysis. The pad plastic defomation in copper thermosonic wire bonding is more critical than gold thermosonic wire bonding. Therefore, copper thermosonic wire bonding will lead to serious pad splashing. Also, quantity of the decreasing of pad plastic deformation was limited by increasing the pad thickness.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24220号 / 工博第5048号 / 新制||工||1788(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 五十嵐 晃, 教授 杉浦 邦征, 教授 KIM Chul-Woo / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

L'objectif de ce travail de thèse est de mettre en place une simulation thermo-mécanique couplée d'une aube revêtue permettant de modéliser l'écaillage de la barrière-thermique qui survient dans les conditions de service de l'aube. La barrière thermique est un revêtement isolant déposé à la surface du substrat monocristallin base Nickel AM1 constitutif de l'aube préalablement recouverte d'une sous-couche. Le mode de dégradation dominant dans ces systèmes est la création de fissures qui résultent de l'accroissement des ondulations hors-plan d'une couche intermédiaire d'oxyde formée en service entre la céramique et la sous-couche. En vue de modéliser ce phénomène d'écaillage, un ensemble d'outils numériques permettant de réaliser un calcul 3D par éléments finis thermo-mécanique couplé de l'aube revêtue est développé au sein du code de calcul par éléments finis Z-set. L'insertion d'éléments de zone cohésive mécanique et thermique au niveau de l'interface barrière-thermique/substrat permet de tenir compte simultanément des changements dans le processus de transert de charge et des variations du flux de chaleur causés par l'amorçage et la propagation d'une fissure interfaciale. L'élément fini d'interface mixte de Lorentz qui repose sur un Lagrangien augmenté, est mis en oeuvre. Afin de tenir compte des propriétés structurelles du revêtement, la modélisation de la barrière thermique est réalisée au moyen d'éléments de coque thermo-mécaniques reposant sur l'approche dite “Continuum Based”. Ces éléments sont développés puis validés dans le cadre de la thèse. La méthode utilisée pour réalier le couplage thermo-mécanique est l'algorithme partitioné CSS (Conventional Serial Staggered) sous-cyclé à pas de couplage fixe dont on montre les limitations dans le cas d'une simulation impliquant la propagation d'une fissure. L'introduction de pas de couplage adaptatifs contrôlés au moyen d'une variable interne du problème mécanique a permis de contourner ces limitations. L'ensemble des briques numériques est validé sur des cas tests de complexité croissante. Des cas d'applications effectués sur des géométries tubulaires à gradient thermique de paroi sont réalisés afin de tester le modèle couplé sur des structures et des chargements proches des conditions de service de l'aube. Enfin, des calculs thermo-mécaniques couplés sur aube revêtue sont présentés. / The purpose of this thesis is to perform a coupled thermomechanical simulation of the failure of thermal barrier coatings for turbine blades under service conditions. The thermal barrier coating is an insulating component applied to the single crystal Nickel-based superalloy AM1 substrate which is covered with a bond coat beforehand. The main degradation mode of those systems is due to the initiation and propagation of cracks caused by the out-of-plane undulation growth of an oxide layer formed in service. A set of numerical tools is implemented into the Finite Element code Z-set in order to perform a 3D thermomechanically coupled simulation of the failure of thermal barrier coatings for turbine blades. Inserting thermomechanical cohesive zone elements at the interface between the coating and the substrate makes it possible to account for the changes in the load transfer and the variations in the heat flux as a consequence of interface degradations. The mixed finite interface element of Lorentz based on an Augmented Lagrangian is used. The thermal barrier coating is modelled by means of thermomechanical shell elements implemented using the Continuum-Based approach to take advantage of the structural properties of the coating layer. Moreover, the partitionned CSS (Conventional Serial Staggered) algorithm used to couple thermal and mechanical problems is assessed. The limitations of sub-cycling with constant coupling time-step are shown through a simulation with crack propagation. The introduction of adaptative time-stepping allows to circumvent that issue. The numerical tools are assessed on test cases with increasing complexity. Numerical simulations on cylindrical tube with a thermal through-thickness gradient are performed with realistic loading sequences. Finally, thermomechanical simulations on turbine blades covered with thermal barrier coating are shown.

Cette étude est consacrée à la modélisation du comportement thermo-mécanique des argiles raides saturées et au développement d'un algorithme d'intégration efficace de contrainte correspondant. Le comportement mécanique de l'argile de Boom naturelle dans des conditions isothermes a été caractérisé. Le modèle Cam Clay modifié (MCC) a été ensuite appliquée pour simuler le comportement de l'argile de Boom naturel. Il a été constaté que le MCC donne des prédictions de mauvaise qualité pour le comportement de l'argile de Boom naturel. Ainsi, un modèle Cam Clay (ACC-2) adapté a été développé en introduisant une nouvelle surface de charge et un nouveau potentiel plastique ainsi que d'un mécanisme plastique de Deux surfaces. Ce modèle permet la description satisfaisante des caractéristiques principales du comportement mécanique de l'argile de Boom naturelle. De plus, les équations de ce modèle peuvent être formulées mathématiquement comme dans un modèle élasto-plastique classique. L'algorithme d'intégration de contrainte classique peut donc être appliqué. Les effets thermiques ont été examinés par l'évaluation de la pertinence de trois lois thermomécaniques avancées (Cui et al, 2000; Abuel-Naga et al, 2007; Laloui et François, 2008; 2009). Il apparaît que tous les trois modèles peuvent décrire les caractéristiques principales du comportement thermo-mécanique des argiles saturées. Cependant, chaque modèle a ses limites ou des points peu clairs du point de vue théorique. L'algorithme d'intégration de contrainte du modèle thermo-mécanique de Cui et al. (2000) au point de contrainte a également été développé spécifiquement en utilisant une méthode adaptive du pas de temps. Le temps de calcul nécessaire pour obtenir une précision donnée est ainsi largement réduit pour des chemins de chargements thermiques et mécaniques. Un modèle thermo-mécanique à Deux surfaces (modèle TEAM) a été développé en se basant sur le mécanisme plastique de Deux surfaces. Le modèle proposé a étendu le modèle de Cui et al. (2000) à une formulation de Deux surfaces considérant le couplage entre les déformations plastiques des chemins de chargements thermiques et mécaniques. La simulation des essais drainés montre que ce modèle peut décrire les caractéristiques principales thermo-mécaniques de l'argile de Boom naturelle le long de différents chemins de chargements. Le modèle TEAM a finalement été étendu à des conditions non drainées. Après la clarification du concept des contraintes effectives et la définition d'une condition de déformation volumique, le processus d'échauffement non drainé est analysé. La validité des équations thermo-hydro-mécaniques de ce modèle a été examinée en se basant sur des résultats d'essais typiques / This study is devoted to the thermo-mechanical constitutive modeling for saturated stiff clays and the development of a corresponding efficient stress integration algorithm. The mechanical behavior of natural Boom Clay in isothermal conditions was first characterized. The Modified Cam Clay model (MCC) was then applied to simulate the natural Boom Clay behavior. It has been found that the MCC gives poor-quality predictions of the natural Boom Clay behavior. Thereby, an adapted Cam Clay model (ACC-2) was developed by introducing a new yield surface and a new plastic potential as well as a Two-surface plastic mechanism. This model allows satisfactory prediction of the main features of the mechanical behavior of natural Boom Clay. Moreover, the constitutive equations of this model can be formulated mathematically as in a classic elasto-plastic model. Thus, the classic stress integration algorithm can be applied. The thermal effects were considered by assessing the performance of some advanced thermo-mechanical models (Cui et al., 2000; Abuel-Naga et al., 2007; Laloui and François, 2008; 2009). It appears that all the three models can capture the main features of the thermo-mechanical behavior of saturated clays. However, each constitutive model has its own limitations or unclear points from the theoretical point of view. The stress integration algorithm of the thermo-mechanical model proposed by Cui et al. (2000) at the stress point level was also developed using a specifically designed adaptive time-stepping scheme. The computation time required to achieve a given accuracy is largely reduced with the adaptive sub-stepping considered for both mechanical and thermal loadings. A Two-surface thermo-mechanical model (TEAM model) was developed based on the Two-surface plastic mechanism. The proposed model extends the model of Cui et al. (2000) to a Two-surface formulation, considering the plastic strain coupling between the thermal and the mechanical loading paths. The simulation of drained tests shows that this model can capture the main thermo-mechanical features of natural Boom Clay along different loading paths. The TEAM model was finally extended to undrained conditions. After setting up an appropriate effective stress principle and defining a volumetric strain condition, the undrained heating process was analyzed. The validity of the thermo-hydro-mechanical constitutive equations was examined based on the data from typical tests

Le comportement des alliages à mémoire de forme (AMF) et des alliages à mémoire de forme magnétiques (AMFM) est régi par les mécanismes de transformation martensitique à l'échelle de la microstructure, à l'origine de leurs propriétés remarquables (mémoire de forme, superélasticité, grandes déformations associées à la réorientation martensitique sous champ magnétique). Les mécanismes de transformation et de réorientation martensitique peuvent être induits par des sollicitations thermiques, magnétiques et / ou mécaniques et de manière couplée. La mise au point d'outils de conception fiables nécessite une meilleure prédictibilité du comportement réel des alliages à mémoire de forme sous sollicitations thermo - magnéto - mécaniques complexes.Le choix d'une modélisation multiaxiale et multi échelle est pertinent. Le modèle reporté présente une formulation unifiée, permettant de simuler aussi bien le comportement des AMF que celui des AMFM.Parallèlement au développement de ce modèle, une étude expérimentale est nécessaire afin d'une part d'identifier les propriétés intrinsèques des matériaux étudiés, et d'autre part de valider les estimations de la modélisation. A cette fin, des mesures de fractions volumiques de phase par diffraction des rayons X in situ ont été entreprises lors de sollicitations thermiques (cycles de chauffage-refroidissement), mécaniques (traction, compression, essais biaxiaux) et magnétiques (champ magnétique unidirectionnel). L'exploitation des résultats de diffractométrie permet une analyse quantitative des fractions volumiques des phases en présence. Celles-ci sont comparées aux estimations du modèle à des fins de validation. / The behavior of shape memory alloys (SMA) and magnetic shape memory alloys (MSMA) is governed by the martensitic transformation mechanisms at the scale of the microstructure. This transformation is at the origin of their remarkable properties (memory effect, superelasticity, large deformations associated with the martensitic reorientation under magnetic field). The martensitic transformation and reorientation mechanisms can be induced by thermal, magnetic and / or mechanical stresses and in a coupled manner. The development of reliable design tools requires a better predictability of the actual behavior of shape memory alloys under complex thermal-magneto-mechanical loading.The choice of multiaxial and multiscale modeling is relevant. The model proposed in this work presents a unified formulation, making possible to simulate both the behavior of SMA and MSMA.In parallel with the development of this model, an experimental study is necessary in order to identify the intrinsic properties of the materials studied and to validate the estimates of the modeling. For this purpose, measurements of phase fractions by in-situ X-ray diffraction were carried out during thermal (heating-cooling cycles), mechanical (tensile, compressive, biaxial) and magnetic (unidirectional magnetic field) loadings. The diffraction patterns allow a quantitative estimation of the volume fractions of the phases. These are compared to model estimates for validation purposes.

This study is devoted to the thermo-mechanical constitutive modeling for saturated stiff clays and the development of a corresponding efficient stress integration algorithm. The mechanical behavior of natural Boom Clay in isothermal conditions was first characterized. The Modified Cam Clay model (MCC) was then applied to simulate the natural Boom Clay behavior. It has been found that the MCC gives poor-quality predictions of the natural Boom Clay behavior. Thereby, an adapted Cam Clay model (ACC-2) was developed by introducing a new yield surface and a new plastic potential as well as a Two-surface plastic mechanism. This model allows satisfactory prediction of the main features of the mechanical behavior of natural Boom Clay. Moreover, the constitutive equations of this model can be formulated mathematically as in a classic elasto-plastic model. Thus, the classic stress integration algorithm can be applied. The thermal effects were considered by assessing the performance of some advanced thermo-mechanical models (Cui et al., 2000; Abuel-Naga et al., 2007; Laloui and François, 2008; 2009). It appears that all the three models can capture the main features of the thermo-mechanical behavior of saturated clays. However, each constitutive model has its own limitations or unclear points from the theoretical point of view. The stress integration algorithm of the thermo-mechanical model proposed by Cui et al. (2000) at the stress point level was also developed using a specifically designed adaptive time-stepping scheme. The computation time required to achieve a given accuracy is largely reduced with the adaptive sub-stepping considered for both mechanical and thermal loadings. A Two-surface thermo-mechanical model (TEAM model) was developed based on the Two-surface plastic mechanism. The proposed model extends the model of Cui et al. (2000) to a Two-surface formulation, considering the plastic strain coupling between the thermal and the mechanical loading paths. The simulation of drained tests shows that this model can capture the main thermo-mechanical features of natural Boom Clay along different loading paths. The TEAM model was finally extended to undrained conditions. After setting up an appropriate effective stress principle and defining a volumetric strain condition, the undrained heating process was analyzed. The validity of the thermo-hydro-mechanical constitutive equations was examined based on the data from typical tests