L’accroissement des besoins en énergie électrique pour les systèmes embarqués et leur augmentation de puissance nécessitent de concevoir des systèmes d’électronique de puissance toujours plus performants. Une solution d’avenir concerne la mise en œuvre de composants à base de diamant qui permettent l’augmentation conséquente des tensions et courants mis en jeux, mais aussi de la température maximale de jonction admissible. Le cadre de ces travaux est celui du projet de recherche Diamonix 2, qui concerne l’étude et l’élaboration d’un composant diamant fonctionnant à haute température. L’objectif du travail doctoral présenté ici est l’étude du packaging haute température de ce type de composant diamant. Plusieurs choix de matériaux et de techniques aptes à l’élaboration d’un assemblage de puce diamant sur un substrat métallisé ont été effectués. La caractérisation microstructurale et mécanique de trois types de jonctions ont été réalisées (refusion d’un alliage AuGe, frittage de nano pâtes d’argent et diffusion en phase solide d’indium dans des couches d’argent). Des essais mécaniques de cisaillement de divers assemblages ont permis d’évaluer le comportement thermomécanique des jonctions et des interfaces. Les essais de cisaillement ont servi à l’identification inverse des paramètres interfaciaux d’un modèle de zones cohésives, pour différents types d’interfaces. Des modèles éléments finis d’assemblage, incluant le comportement viscoplastique des jonctions et des lois d’endommagent des interfaces, ont servi à simuler le comportement thermomécanique du packaging d’un composant diamant. / The increase of electric power demand for embedded systems requires more efficient power electronics modules. A solution to reach this goal relates to the use of diamond-based components that allow high voltage, current density and the maximum allowable junction temperature. The framework is the same as that of the Diamonix 2 research project, which involves the elaboration and the study of a diamond-based die dedicated to high temperature environment. The purpose of the present work is to optimize and simulate the thermomechanical behavior of high temperature diamond die packaging. To reach this goal, the choice of materials that allow high temperature assemblies of diamond die/ceramic substrate was done (AuGe solder alloy, sintering of nano-silver paste, transient liquid phase bounding of indium in silver layers). Microstructural and mechanical characterization of the attachment and the diamond die/junction was realized. Nanoindentation and shear tests are performed for the mechanical characterization. Shear tests results carried out on the two assemblies have been used to identify the interfacial parameters of the bilinear cohesive zone model (CZM) for the diamond die/junction and ceramic substrate/junction interfaces. Finite element modelling of the diamond component packaging including viscoplastic behavior of the junctions and damage law of the interfaces of assemblies were built.

Analisam-se problemas de interação solo-estrutura através de uma formulação tridimensional obtida da combinação entre o Método dos Elementos de Contorno (MEC) e o Método dos Elementos Finitos (MEF). Os elementos estruturais que interagem com o solo são modelados pelo Método dos Elementos Finitos. E o solo, considerado como um meio semi-infinito, homogêneo, elástico linear e isotrópico, é modelado pelo Método dos Elementos de Contorno, empregando a solução fundamental de Mindlin. A solução fundamental de Mindlin é particularmente adequada para o tipo de problemas em análise, ou seja, problemas envolvendo sólidos tridimensionais semi-infinitos, já que é necessário discretizar apenas a superfície carregada do solo e/ou a linha de carga, e não todo o sólido tridimensional. A discretização da estaca em vários elementos finitos de viga tridimensional, permitindo a consideração de estacas de qualquer tamanho e submetidas a qualquer tipo de carregamento é uma das principais contribuições do trabalho. Outra contribuição diz respeito à consideração da ação horizontal no sistema placa-estaca-solo, diretamente aplicada na placa, e não redistribuída no topo das estacas. Por isso, os elementos estruturais laminares (radiers, sapatas e blocos de fundação) são modelados por elementos finitos de casca plana, possibilitando a consideração dos efeitos de flexão e de membrana. Essa abordagem permite a análise tanto de um grupo de estacas com bloco de capeamento rígido quanto de um radier estaqueado de qualquer rigidez. O acoplamento entre o MEC e o MEF é feito através de uma formulação mista em que a matriz dos coeficientes de influência do solo obtida pelo MEC é adicionada à matriz de rigidez dos elementos estruturais obtida pelo MEF, resultando em uma matriz de rigidez equivalente. Exemplos numéricos de interação estaca-solo, placa-solo e casca plana-estaca-solo são resolvidos para verificar, validar e demonstrar a eficiência das formulações desenvolvidas e implementadas. / Soil-structure interaction problems are analyzed by a tridimensional formulation obtained combining the Boundary Element Method (BEM) and the Finite Element Method (FEM). Structural elements that interact with the soil are modeled by the Finite Element Method. And the soil, considered as a semi-infinite, homogeneous, linear elastic and isotropic medium, is modeled by the Boundary Element Method, using Mindlin\'s fundamental solution. Mindlin\'s fundamental solution is particularly suitable for the type of problems under analysis, viz. problems involving semi-infinite three-dimensional solids, since it is necessary to discretize only the loaded surface of the soil and/or the line-load, and not all the three-dimensional solid. The discretization of the pile in several three-dimensional beam finite elements, allowing the consideration of piles of any size and subjected to any type of loading, is one of the main contributions of this work. Another contribution is about the consideration of the horizontal load in the plate-pile-soil system, directly applied to the plate, and not redistributed on the top of the piles. Therefore, the laminar structural elements (rafts, footings, and foundation blocks) are modeled by flat shell finite elements, making possible the consideration of the effects of flexion and membrane. This approach allows the analysis of both a capped pile group and a piled raft of any stiffness. The coupling between the BEM and the FEM is performed through a mixed formulation in which the matrix of the soil\'s influence coefficients obtained by the BEM is added to the stiffness matrix of the structural elements obtained by the FEM, resulting in an equivalent stiffness matrix. Numerical examples of pile-soil, plate-soil and flat shell-pile-soil interaction are solved to verify, validate and demonstrate the efficiency of the developed and implemented formulations.

O estudo do comportamento mecânico do complexo sistema advindo da interação entre solo/subestrutura/superestrutura é o tema do trabalho. Neste contexto, a representação do maciço é feita usando-se o método dos elementos de contorno (MEC) em abordagem 3D, de maneira que se possa simular o maciço com características mecânicas não-homogêneas, além de se considerar uma camada de apoio indeslocável a distâncias prescritas a priori e condição de aderência perfeita. A subestrutura também é representada via MEC tridimensional, a qual está imersa dentro deste meio heterogêneo. A infra e a superestrutura são modeladas empregando o método dos elementos finitos (MEF), com o uso de elementos estruturais reticulares e elementos laminares. São apresentados alguns exemplos em que se valida a formulação e outros que demonstram a potencialidade e a necessidade de se empregar a formulação para a melhor análise do complexo fenômeno em estudo. Por fim, demonstra-se a obrigatoriedade de se otimizar a formulação, empregando-se duas grandes ferramentas numéricas: o paralelismo e o emprego de um adequado método de resolução de sistemas esparsos. / The analysis of the soil-structure system interaction is a vast field of interest in the area of civil engineering. A realistic representation of its behaviour. Thus, in the present research, the soil is considered a non-homogeneous continuum supported by a rigid and adhesive interface and modelled by boundary element method via Kelvin solution in 3D space. The foundation is also modelled by this above-mentioned modelling technique. The raft foundation and the superstructure are represented by finite shell and 3D frame elements. In order to estimate the accuracy and the potentiality of the proposed numerical formulation, some examples are validated when compared to similar approaches, and others simulations are presented to stress the necessity of coupling the non-homogeneous soil-foundation-radier-superstructure system as a whole. Finally, to acquire numerical time efficiency, it is shown that it is imperative to apply parallel processing and sparse techniques for the solution of the final system.

No presente trabalho, uma combinação do método dos elementos de contorno (MEC) com o método dos elementos finitos (MEF) é apresentada para a análise da interação entre estacas e o solo, considerado como um meio infinito tridimensional e homogêneo. O meio contínuo tridimensional de domínio infinito é modelado pelo MEC, enquanto as estacas consideradas como elementos reticulares são tratadas pelo MEF. As equações das estacas oriundas do método dos elementos finitos são combinadas com as do meio contínuo obtidas a partir do método dos elementos de contorno, resultando em um sistema completo de equações, que convenientemente tratadas, proporcionam a formulação de coeficientes de rigidez do conjunto solo-estacas. Finalmente, uma formulação para a análise do comportamento não-linear do solo na interface com a estaca é desenvolvida, tornando o modelo mais abrangente. / In the present work a combination of the Boundary Element Method (BEM) and the Finite Element Method (FEM) is used for pile-soil interaction analyses, considering the soil as a homogeneous, three-dimensional and infinite medium. The three-dimensional infinite continuous medium is modeled by the BEM, and the piles are, considered as beam elements, modeled by the FEM. This combination also is used for studying the interaction of plates sitting on a continuous medium. The pile equations generated from the FEM are combined with the medium equations generated from the BEM, resulting a complete equation system. Manipulating properly this equation system, a set of stiffness coefficients for the system soil-pile is obtained. Finally, to make the model more comprehensive, it presented a formulation to take into account the soil nonlinear behavior at the pile interface.

Neste trabalho, propõe-se uma formulação não linear baseada no método dos elementos de contorno, para representação de domínios poro-elasto-plásticos reforçados. Esta formulação é apresentada para os casos saturado e não saturado. Para o problema poroso enrijecido um acoplamento com o método dos elementos finitos é empregado, e a técnica de mínimos quadrados permite a regularização dos deslocamentos e do vetor de forças de superfície ao longo das interfaces de acoplamento. São empregadas expressões analíticas para o tratamento das integrais de contorno e de domínio presentes na formulação do método dos elementos de contorno. A formulação de Biot é empregada para a descrição de meios porosos saturados e uma formulação energética baseada nos trabalhos de Coussy é adaptada para a extensão ao caso não saturado. Neste caso, a pressão capilar e energia das interfaces são levadas em consideração. O nível de saturação é descrito pelo modelo de Van Genuchten e o comportamento do esqueleto é descrito ou pelo modelo de Drucker-Prager ou pelo modelo de Cam-Clay modificado. O problema não linear obtido por uma descrição temporal associada a discretização espacial é resolvido pelo método de Newton-Raphson. No caso saturado, o operador tangente consistente é definido e utilizado para obtenção da solução do sistema. Exemplos numéricos são apresentados para validar a formulação proposta. / In this work a nonlinear formulation of the boundary element method (BEM) is proposed to deal with saturated and unsaturated poro-elasto-plastic 2D reinforced domains. To model reinforced porous domains a BEM/FEM (Finite Element Method) modified coupling technique is employed. The coupling is made by using the least square method to regularize the displacement and traction distributions along the interfaces. Analytical expressions have been derived for all boundary and domain integrals required for the formulation. The Biot formulation is used for the description of the saturated porous environments and an energetic consistent formulation based on work of Coussy is adopted for its extension to the framework of unsaturated porous media. In this case, the capillar pressure and the interface energy are taken into account. The Van Genuchten model is used for the determination of saturation level in non-saturated poro-elasto-plastic problems. The Drucker-Prager modified model if used for the saturated poro-elasto-plastic problems and the modified Cam-Clay model for the representation of non-saturated poro-elasto-plastic problems. For the saturated case, the consistent tangent operator is derived and employed inside a Newton procedure to solve non-linear problems. Numerical solutions are presented to validate the proposed models.

O objetivo do presente trabalho é o desenvolvimento de um código computacional que possibilite a análise dinâmica de estruturas tridimensionais em regime elástico-linear acopladas ao solo, tratado como meio infinito elastoplástico. As superestruturas são tratadas por elementos finitos simples de casca e de barra geral, as estruturas de fundações são tratadas por elementos de casca que simulam o contato com o solo, modelando radiers, túneis e reservatórios enterrados. Blocos são modelados por elementos de contorno tridimensionais. O solo é modelado de duas maneiras distintas: na região plastificada emprega-se a solução fundamental de Kelvin (estática) e na região não plastificada (elástica) adota-se a solução fundamental do problema de Stokes. O acoplamento entre os meios é feito aplicando-se a técnica de subregiões. Deve ficar claro que todo procedimento estático equivalente foi implementado. Vários exemplos numéricos são apresentados, onde se percebe a eficiência do código computacional desenvolvido / The objective of the present work is the development of a computational code that makes possible dynamic analyses of three-dimensional structures in elastic-linear behavior coupled to the soil, modeled as elastoplastic infinite medium. Simple finite elements, shell and general bars, are used to model elastic structures. The structures of foundations are modeled by shell’s elements which simulate the contact with the soil, modeling radiers, tunnels and buried reservoirs. Blocks are modeled by three-dimensional boundary elements. The soil is modeled in two different ways: in the plastic region Kelvin’s fundamental solution (static) is used and in the elastic region the fundamental solution of the Stoke’s problem is adopted. The coupling among the media is done applying the sub-region technique. It is important to note that the equivalent static procedure has been implemented. Several numerical examples are presented, demonstrating the efficiency of the developed computational code

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-06-21T11:44:49Z No. of bitstreams: 1 aldemonlagebonifacio.pdf: 14222882 bytes, checksum: a77833e828dc4a72cf27e6608d6e0c5d (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-07T19:04:13Z (GMT) No. of bitstreams: 1 aldemonlagebonifacio.pdf: 14222882 bytes, checksum: a77833e828dc4a72cf27e6608d6e0c5d (MD5) / Made available in DSpace on 2017-08-07T19:04:13Z (GMT). No. of bitstreams: 1 aldemonlagebonifacio.pdf: 14222882 bytes, checksum: a77833e828dc4a72cf27e6608d6e0c5d (MD5) Previous issue date: 2017-03-16 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O concreto feito com agregados leves, ou concreto leve estrutural, é considerado um material de construção versátil, bastante usado em todo o mundo, em diversas áreas da construção civil, tais como, edificações pré-fabricadas, plataformas marítimas, pontes, entre outros. Porém, a modelagem das propriedades mecânicas deste tipo de concreto, tais como o módulo de elasticidade e a resistência a compressão, é complexa devido, principalmente, à heterogeneidade intrínseca aos componentes do material. Um modelo de predição das propriedades mecânicas do concreto de agregado leve pode ajudar a diminuir o tempo e o custo de projetos ao prover dados essenciais para os cálculos estruturais. Para esse fim, este trabalho visa desenvolver uma estratégia computacional para a avaliação de propriedades mecânicas do concreto de agregado leve, por meio da combinação da modelagem computacional do concreto via MEF (Método de Elementos Finitos), do método de inteligência computacional via SVR (Máquina de vetores suporte com regressão, do inglês Support Vector Regression) e via RNA (Redes Neurais Artificiais). Além disso, com base na abordagem de workflow científico e many-task computing, uma ferramenta computacional foi desenvolvida com o propósito de facilitar e automatizar a execução dos experimentos científicos numéricos de predição das propriedades mecânicas. / Concrete made from lightweight aggregates, or lightweight structural concrete, is considered a versatile construction material, widely used throughout the world, in many areas of civil construction, such as prefabricated buildings, offshore platforms, bridges, among others. However, the modeling of the mechanical properties of this type of concrete, such as the modulus of elasticity and the compressive strength, is complex due mainly to the intrinsic heterogeneity of the components of the material. A predictive model of the mechanical properties of lightweight aggregate concrete can help reduce project time and cost by providing essential data for structural calculations. To this end, this work aims to develop a computational strategy for the evaluation of mechanical properties of lightweight concrete by combining the concrete computational modeling via Finite Element Method, the computational intelligence method via Support Vector Regression, and via Artificial Neural Networks. In addition, based on the approachs scientific workflow and many-task computing, a computational tool will be developed with the purpose of facilitating and automating the execution of the numerical scientific experiments of prediction of the mechanical properties.

L'utilisation des composites dans la construction des bâtiments ou des ouvrages d'art est de plus en plus importante car ces matériaux présentent des atouts indiscutables comme un très bon rapport performance / poids ou une facilité de mise en oeuvre. Cependant, leur essor est ralenti par certaines faiblesses dont l'une des plus importantes est leur souplesse qui induit des déplacements élevés et des risques d'instabilités importants qui ne permettent pas d'exploiter tout le potentiel de ces matériaux. Dans le cas d'éléments de structure fléchis, une des solutions consiste à associer les profilés composites à une dalle en béton armé. La connexion est établie par des butées mécaniques, par collage, ou l'association des deux. L'objectif général de ce travail est d'étudier le comportement des structures mixtes GFRP-Béton fléchies sous chargement statique instantané : Cette étude comporte un volet expérimental lourd et un volet de modélisation numérique. Elle a été abordée à 3 échelles : matériaux, interface, et structure. Trois modes de connexion ont été exploités. Sur le plan expérimental, nous avons d'abord caractérisé tous les matériaux utilisés : composite, béton, adhésif, acier des armatures et des connecteurs. Puis, la caractérisation à l'échelle de l'interface a été effectuée par l'essai push-out dans différentes configurations (7 séries d'essais au total). Enfin, le comportement à l'échelle d'éléments de structure a été étudié sur des mono-poutres pour des portées allant de 2 m à 4.8 m, sur des poutres composites seules ou sur des poutres mixtes (10 poutres au total). Une passerelle bi-poutre de 4.8 m de portée a également été testée dans la même configuration et jusqu'à la ruine. La modélisation du comportement de ces poutres hybrides a été effectuée selon 2 cas théoriques. Elles ont d'abord été modélisées dans le cadre de la théorie des poutres multicouches, dans le domaine élastique et à l'approche de la ruine. Selon le mode de connexion, le glissement à l'interface est pris en compte ou négligé. Ces poutres ont également été modélisées par la MEF en utilisant des éléments volumiques et en considérant une connexion parfaite. Les résultats d'essais montrent le comportement correspondant à chaque mode de connexion : la connexion par butées mécaniques simples est à ce jour celle qui s'avère la plus efficace. Les écarts modèle / calculs restent acceptables sauf à proximité de l'interface où les déformations peuvent être affectées par la fissuration du béton qui reste difficile à prédire de façon précise. La simulation numérique donne des valeurs très proches de la réalité et répond aux questions posées lors de l'expérience / Advanced composites are increasingly used in construction thanks to their indisputable advantages such as high strength to weight ratio and ease of implementation. However, their growth is hindered by a main weak point: low stiffness. Advanced composites risk instabilities under high loads which make it not possible to exploit their full potential. Considering flexural elements, one of the solutions proposed consists in associating the composite profiles with a reinforced concrete slab. The connection of both materials is either established by bolting, bonding or a combination of both techniques.In this study, 3 different connection modes were tested on structural elements with different spans. Previously, to characterize the mechanical behavior of the interface, 35 push out specimens having bolted or bonded connections were prepared and tested. In addition, all materials used were characterized.A composite beam (Pu1) and 8 hybrid beams (PB1-PB8) were tested under 3 points bending up to failure. The results are exploited to construct and test a hybrid footbridge. 7 push out series were tested and digital image correlation was used to analyze the behavior at the interface and measure the displacement fields to determine the slip. Concrete, GFRP, bolts, the adhesive and the concrete reinforcing steel bars were all characterized.The experimental data obtained from the tests is compared to calculation results obtained by a multi-layer beam model within service limit states and at ultimate ones. Besides, a 3D finite element model was developed to provide more accurate results.The results allow distinguishing 3 behavior modes relative to the 3 connection types: the connection by mechanical studs proves to be the most efficient so far. The measurements are also compared to the results obtained by a multi-layer beam model. The differences are acceptable except in the vicinity of the interface where the deformations can be affected by the cracking of the concrete which remains difficult to predict precisely. The 3D simulations present with an excellent agreement the experiments and explain some observations obtained

Au sein des opérations de retraitement du combustible usé, la colonne pulsée à garnissage est l'appareil d'extraction liquide-liquide principalement utilisé. Dans un contexte de compétitivité économique et de raréfaction des ressources, l'efficacité de ces appareils est devenue un enjeu pour l'industriel. Afin d'améliorer leur rendement à travers un meilleur dimensionnement, la connaissance de la vitesse de glissement entre les phases de l'émulsion est nécessaire.Les travaux menés et présentés dans ce manuscrit s'articulent autour de la modélisation physique et numérique de l'hydrodynamique de l'émulsion ainsi que de sa caractérisation expérimentale.Dans ce travail, une modélisation d'approche eulérienne, inspirée des travaux de D. Lhuillier, permet l'obtention d'un modèle bi-fluide couplé à une équation d'évolution de la surface d'échange (aire interfaciale). La résolution du modèle s'effectue par éléments finis sous le logiciel CAST3M. A l'issue des calculs, le modèle montre sa capacité à restituer le comportement de l'émulsion et permet l'obtention des vitesses de glissement. Dans une optique de validation expérimentale du modèle, des expérimentations sur deux installations sont menées. Celles-ci font notamment intervenir un couplage entre les méthodes de vélocimétrie par image de particules et de fluorescence induite par laser afin d'obtenir les vitesses de chaque phases et le taux de rétention de la phase dispersée. Un algorithme de détection et de suivi de gouttes est développé afin d'obtenir la vitesse de la phase dispersée et sa fraction volumique. La confrontation de ces aux résultats numériques permet une première qualification encourageante du modèle. / In the core of spent fuel reprocessing operations, the pulsed columns with packing are the liquid-liquid extraction apparati mainly used. The context of economical competiveness and scarce resources, industrials are driven to improve the efficiency of these processes. Pulsed column efficiency is bound to the amount of available exchange surface, which depends on geometrical parameters of the column and the operating conditions. A better design would improve the efficiency. In this aim the knowledge of the interphase slip velocity is necessary. The work presented in this thesis revolves around physical and numerical modelling of the hydrodynamics of the emulsion and its experimental characterization.In this work, a eulerian approach, based on the work of D.Lhuillier, allows to obtain a two-fluid model coupled with an evolution equation of the exchange surface (interfacial area). We use finite elements method to solve this model along with CAST3M software. Numerical simulations have shown the model abilities to correctly reproduce the emulsion behaviour and to obtain the slip velocity.In order to experimentally validate the model, we carried out two types of experimentation. Particles images velocimetry coupled to laser induced fluorescence are involved to obtain velocities of each phases and the dispersed phase volume fraction. We developed a tracking algorithm to obtain the dispersed phase velocity and the hold up. These results, such as velocities and strain rate tensor, have been used in a first validation of the model.

This thesis deals with the measurement of transmission parameters in the new generation access networks NGA. The aim of the thesis is to build and configure a test network and scenarios for the measurement of service quality parameters and then verify the transmission stability. The theoretical part describes general functioning of NGN networks, the requirements of different telecommunications services on quality parameters, methodology and recommendations for measuring transmission parameters in packet networks. The practical part deals with the configuration of scenarios using mainly MPLS technology and methodology of their testing. Measurements were performed according to recommendations IETF RFC 2544, IETF RFC 6349 with the ExacTCP test and ITU-T Y.1564 with the EtherSAM test. For measurements were used measuring instruments of EXFO brand. In conclusion, the measurement results according to the mentioned standards were evaluated and also the advantages of using the measurement according to the given standard in NGA access networks were discussed.