O crescente desempenho das aeronaves aliado ao desenvolvimento de materiais cada vez mais leves e flexíveis tem levado os projetistas a utilizar coeficientes de segurança estruturais cada vez menores, o que pode tornar as superfícies aerodinâmicas mais susceptíveis a fenômenos aeroelásticos, entre eles o flutter, que deve ser cuidadosamente investigado com ensaios em solo e em voo durante o desenvolvimento e certificação de aeronaves. Para tais ensaios, é importante uma instrumentação adequada, que possa prever o aparecimento de vibrações indesejadas e possa agir de forma menos intrusiva possível, de forma a não modificar o comportamento dinâmico do sistema. Esse trabalho propõe o uso do imageamento infravermelho como instrumento para detecção de flutter, analisando se essa técnica é adequada para tal aplicação e quais as vantagens e desvantagens de seu uso. Para isso é feita uma revisão da literatura pertinente, apresentando conceitos de flutter, mecânica estrutural e tecnologia infravermelho, e em seguida é apresentada uma estrutura conhecida para se testar a técnica referida. São realizados simulações e testes na estrutura para levantamento das suas características e finalmente testes em túnel de vento, onde se verifica o funcionamento desta técnica, seus pontos positivos e pontos que requerem melhorias. / The increasing performance of aircraft together with the development of increasingly lightweight and flexible materials has led designers to use smaller structural safety factors, which can make the aerodynamic surfaces more susceptible to aeroelastic phenomena, including flutter, which should be carefully investigated with ground and flight tests during the aircraft development and certification. For such assays, it is important to use proper instrumentation, which can predict the occurrence of unwanted vibrations to act in less intrusive way possible, in order to not modify the system dynamic behavior. This work proposes the use of infrared imaging as a tool for detection of flutter, analyzing whether this technique is suitable for such application, the advantages and disadvantages of their use. For this, a review of the relevant literature is made, presenting flutter concepts, structural mechanics and infrared technology, and then a known structure used to test the technique is presented. Simulations and tests to survey the structure characteristics are presented as well as tests in the wind tunnel, performing the operation of this technique in order to address its positive points and areas that needs improvement.

The term “granular material” describes any assembly of macroscopic particles. This broad definition encompasses a wide variety of everyday materials, for example sand, cereals, gravel and powders. However, despite their commonplace nature, to date no universally accepted set of constitutive equations exists to describe the behaviour of these materials. Thermomechanics and micromechanics are two modelling methodologies previously employed in separate efforts to represent granular behaviour. In this thesis, the two theories are integrated to develop new models of idealised granular materials. (For complete abstract open document)

O crescente desempenho das aeronaves aliado ao desenvolvimento de materiais cada vez mais leves e flexíveis tem levado os projetistas a utilizar coeficientes de segurança estruturais cada vez menores, o que pode tornar as superfícies aerodinâmicas mais susceptíveis a fenômenos aeroelásticos, entre eles o flutter, que deve ser cuidadosamente investigado com ensaios em solo e em voo durante o desenvolvimento e certificação de aeronaves. Para tais ensaios, é importante uma instrumentação adequada, que possa prever o aparecimento de vibrações indesejadas e possa agir de forma menos intrusiva possível, de forma a não modificar o comportamento dinâmico do sistema. Esse trabalho propõe o uso do imageamento infravermelho como instrumento para detecção de flutter, analisando se essa técnica é adequada para tal aplicação e quais as vantagens e desvantagens de seu uso. Para isso é feita uma revisão da literatura pertinente, apresentando conceitos de flutter, mecânica estrutural e tecnologia infravermelho, e em seguida é apresentada uma estrutura conhecida para se testar a técnica referida. São realizados simulações e testes na estrutura para levantamento das suas características e finalmente testes em túnel de vento, onde se verifica o funcionamento desta técnica, seus pontos positivos e pontos que requerem melhorias. / The increasing performance of aircraft together with the development of increasingly lightweight and flexible materials has led designers to use smaller structural safety factors, which can make the aerodynamic surfaces more susceptible to aeroelastic phenomena, including flutter, which should be carefully investigated with ground and flight tests during the aircraft development and certification. For such assays, it is important to use proper instrumentation, which can predict the occurrence of unwanted vibrations to act in less intrusive way possible, in order to not modify the system dynamic behavior. This work proposes the use of infrared imaging as a tool for detection of flutter, analyzing whether this technique is suitable for such application, the advantages and disadvantages of their use. For this, a review of the relevant literature is made, presenting flutter concepts, structural mechanics and infrared technology, and then a known structure used to test the technique is presented. Simulations and tests to survey the structure characteristics are presented as well as tests in the wind tunnel, performing the operation of this technique in order to address its positive points and areas that needs improvement.

To safely transport and use energetic materials, it is important that their response to mechanical excitation at various temperatures be well understood. In order to better understand the thermomechanical response of these materials, samples of inert and live PBXN-109 are fabricated and excited between 10-20 kHz. The resonance of the system is found using a Laser Doppler Vibrometer and the temperature at the surface of the sample is measured with an infrared camera. Samples are loaded into an environmental chamber and tested at -10, 22, 55, and 120 ˚C. Using multiple procedures, the shift in resonant frequency caused by changing material properties can be predicted and followed to elicit the greatest thermal response. Twelve samples are excited using a fluctuating sinusoidal input at each temperature range. The samples are shown to generate significantly less heat from mechanical excitation as ambient temperature increases. Heating rates are also severely affected by temperature. Samples tested at 120 ˚C heat at a rate of ~0.5 ˚C/min, while samples at -10 ˚C heat at ~ 5.7 ˚C/min. Despite the large difference in heating rates samples tested at higher ambient temperatures reached higher peak temperatures. This indicates that the strong temperature dependence of the material properties is likely key to reducing heating caused by mechanical excitation. It also indicates that proper control of ambient temperature should be considered when transporting or using munition systems to ensure safety and proper functionality.

Peridynamics is an emerging nonlocal continuum theory which allows governing field equations to be applicable at discontinuities. This applicability at discontinuities is achieved by replacing the spatial derivatives, which lose meaning at discontinuities, with integrals that are valid regardless of the existence of a discontinuity. Within the realm of solid mechanics, the peridynamic theory is one of the techniques that has been employed to model material fracture. In this work, the peridynamic theory is used to investigate different fracture problems in order to establish its fidelity for predicting crack growth. Various fracture experiments are modeled and analyzed. The peridynamic predictions are made and compared against experimental findings along with predictions from other commonly used numerical fracture techniques. Additionally, this work applies the peridynamic framework to model heat transfer. Generalized peridynamic heat transfer equation is formulated using the Lagrangian formalism. Peridynamic heat conduction quantites are related to quanties from the classical theory. A numerical procedure based on an explicit time stepping scheme is adopted to solve the peridynamic heat transfer equation and various benchmark problems are considered for verification of the model. This paves the way for the coupling of thermal and structural fields within the framework of peridynamics. The fully coupled peridynamic thermomechanical equations are derived based on thermodynamic considerations, and a nondimensional form of the coupled thermomechanical peridynamic equations is also presented. An explicit staggered algorithm is implemented in order to numerically approximate the solution to these coupled equations. The coupled thermal and structural responses of a thermoelastic semi-infinite bar and a thermoelastic vibrating bar are subsequently investigated.

Bone cutting is widely used in orthopaedic, dental and neuro surgeries and is a technically demanding surgical procedure. Novel surgical methods are continually introduced in orthopaedic, neuro and dental surgeries and are aimed at minimising the invasiveness of the operation and allowing more precise cuts. One such method that utilises cutting with superimposed ultrasonic vibration is known as ultrasonically- assisted cutting (UAC). The main concern in bone cutting is the mechanical and thermal damage to the bone tissue induced by high-speed power tools. Recent technological improvements are concerned with the efforts to decrease the force required by the surgeon when cutting the bone as well as increases in surgery speed. A programme of experiments was conducted to characterise properties of a bone and get a basic understanding of the mechanics of bone cutting. The experiments included: (a) nanonindentation and tension tests to obtain the properties for the finite element (FE) bone cutting model, (b) high-speed filming to observe the chip formation process, which influences thermomechanics of the cutting process in conventional drilling (CD) and ultrasonically-assisted drilling (UAD) and, (c) plane cutting and drilling experiments to measure the levels of force and temperature rise in the bone tissue. Novel two-dimensional finite element (FE) models of cortical bone cutting were developed for conventional and ultrasonically-assisted modes with the MSC.MARC general FE code that provided thorough numerical analysis of thermomechanics of the cutting process. Mechanical properties such as the elastic modulus and strain-rate sensitivity of the bone material were determined experimentally and incorporated into the FE models. The influence of cutting parameters on the levels of stress, penetration force and temperature in the bone material was studied using conventional cutting (CC) and ultrasonically-assisted cutting (UAC). The temperature rise in the bone material near the cutting edge was calculated and the effect of cutting parameters on the level of thermal necrosis was analysed. The necrosis depth in bone was calculated as a distance from the cut surface to the point where the thermal threshold level was attained. Comparative studies were performed for the developed FE models of CC and UAC of bone and the results validated by conducting experiments and using data from scientific publications. The main outcome of the thesis is an in-depth understanding of the bone cutting process, and of its possible application in orthopaedics. Recommendations on further research developments are also suggested.

A local isotropic damage coupled hyperelastic-plastic framework is formulated in principal axes where thermo-mechanical extensions are also addressed. It is shown that, in a functional setting, treatment of many damage growth models, including ones originated from phenomenological models (with formal thermodynamical derivations), micro-mechanical models or fracture criteria, proposed in the literature, is possible. Quasi-unilateral damage evolutionary forms are given with special emphasis on the feasibility of formulations in principal axes. Local integration procedures are summarized starting from a full set of seven equations which are simplified step by step initially to two and finally to one where different operator split methodologies such as elastic predictor-plastic/damage corrector (simultaneous plastic-damage solution scheme) and elastic predictor-plastic corrector-damage deteriorator (staggered plasticdamage solution scheme) are given. For regularization of the post peak response with softening due to damage and temperature, Perzyna type viscosity is devised. Analytical forms accompanied with algorithmic expressions including the consistent material tangents are derived and the models are implemented as UMAT and UMATHT subroutines for ABAQUS/Standard, VUMAT subroutines for ABAQUS/Explicit and UFINITE subroutines for MSC.Marc. The subroutines are used in certain application problems including numerical modeling of discrete internal cracks, namely chevron cracks, in direct forward extrusion process where comparison with the experimental facts show the predicting capability of the model, isoerror map production for accuracy assessment of the local integration methods, and development two novel necking triggering methods in the context of a damage coupled environment.

La semi-perméation à haute température dans les matériaux conducteurs mixtes introduit des sollicitations chimiques. Ces matériaux sont donc sujets à des déformations d’origine thermique et d’origine chimique qui entraînent des contraintes thermo-chimio-mécaniques dont il convient de tenir compte pour anticiper leur tenue mécanique en service. Ce travail de modélisation en science pour l’ingénieur, intrinsèquement multiphysique, a pour but d’ouvrir la voie au calcul de structures de dimensions industrielles en adoptant une modélisation fonction des paramètres directement mesurables. Il s’articule principalement autour du développement d’un modèle macroscopique de déformation chimique. La modélisation proposée tient compte du transport de l’oxygène en transitoire. Les cinétiques d’échanges de matière à la surface du matériau avec leur conséquence en termes de chocs chimio-mécaniques sont évaluées. Pour simuler le comportement de structures complexes en trois dimensions, en régimes stationnaire et transitoire, les modèles ont été implémentés dans le code de calcul par éléments finis Abaqus. L’application porte sur un réacteur catalytique membranaire pour l’oxydation partielle du méthane en gaz de synthèse. L’histoire des sollicitations thermiques, chimiques et mécaniques rencontrée au cours du cycle de fonctionnement de la structure est prise en compte. La modélisation permet d’évaluer l’impact des conditions opératoires sur la tenue mécanique de la structure. / Technologies using high temperature oxygen transport through mixed conductor materials undergo thermal andchemical expansions. The industrial structures suffer from thermo-chemo-mechanical stresses which may be modeled to predict their mechanical reliability. This work is a step toward the development of design tools for mechanics of structure made of mixed conductor. The goal is to deal with measurable parameters such as temperature and oxygen partial pressure. The first aim is to provide a realistic macroscopic modelling of chemical expansion. The second one is to model the coupling between mechanics, oxygen transport and heat transfer. The oxygen bulk diffusion is described following the Wagner theory. The kinetics of surface exchange and their consequences in terms of chemo-mechanical shocks have been explored. In order to conduct computation of complex structures in three dimensions with steady and transient state, the models have been implemented in finite element analysis software (Abaqus). Comparison with analytical results is also reported. Finally, a semi-industrial catalytic membrane reactor for partial oxidation of methane to syngas is computed. The modelling helps to analysed the impact of operating conditions on the mechanical reliability of the whole structure.

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No. of bitstreams: 1 Fabiano Alex Colling.pdf: 5692188 bytes, checksum: 8354ca65e4e9e9a92a55f10b5e92b187 (MD5) Previous issue date: 2014-11-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPQ – Conselho Nacional de Desenvolvimento Científico e Tecnológico / FAPERGS - Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul / FINEP - Financiadora de Estudos e Projetos / NUCMAT - Núcleo de Caracterização de Materiais / Programa de Bolsas de Estudo Talentos Tecnosinos / itt Chip - Instituto Tecnológico de Semicondutores da Unisinos / Hongik University da Coreia do Sul / Modelab - Laboratório de Modelagem Elétrica Térmica e Mecânica de Módulos e Encapsulamentos e Eletrônicos / O desenvolvimento de novas tecnologias de encapsulamento de semicondutores tem diminuído o tamanho das trilhas das placas de circuito impresso em busca da miniaturização. Esta diminuição está chegando ao limite possível de ser construído pelo fato de apresentar problemas, como aumento da resistência, ou por ruptura por eletromigração, além do aumento do custo para o controle de partículas nas salas limpas de fabricação. O Encapsulamento sobre Encapsulamento (Package on Package - PoP) surge como uma proposta de encapsulamento com empilhamento de chips finos para reduzir a ocupação do chip na placa. A diferença de propriedades térmicas e mecânicas dos diferentes materiais que compõem o chip encapsulado pode resultar no empenamento do componente. Neste trabalho, foi simulado o comportamento termomecânico de um dispositivo eletrônico encapsulado pela tecnologia Package on Package. Foi avaliado, do ponto de vista térmico e mecânico, quais são os fatores geradores do empenamento de semicondutores encapsulados com a tecnologia PoP recorrente no processo de moldagem. As condições e parâmetros de processo de fabricação foram estudados durante a fabricação de um protótipo de chip de 40 µm de espessura e moldado com um composto de epóxi do tipo 2 (Epoxy Molding Compound - EMC) realizado no Laboratório de Materiais do Departamento de Ciências dos Materiais e Engenharia da universidade Hongik da Coreia do Sul, parceira no projeto de pesquisa. Através das medições do empenamento, por interferometria de Moiré, realizadas no laboratório de testes da empresa Sul Coreana Hana Micron, foi possível construir correlações com a simulação computacional deste componente. Os resultados desta comparação foram utilizados como base para a validação da simulação e ajustes de dados de entrada utilizados em outras três espessuras diferentes de chip de silício (70, 100 e 200 µm) e dois tipos diferentes de EMC (EMC1 e EMC2). As condições e parâmetros de processo de fabricação, a influência no empenamento das diferentes espessuras e tipos de EMC dos componentes simulados foram avaliados. As simulações realizadas com variação no EMC em componentes com chip de 40 µm mostraram que o EMC do tipo 1 apresenta uma redução de 42,39% no empenamento na parte superior do componente (Top) maior em relação ao EMC do tipo 2. No Top, o substrato com chip de 100 µm, o empenamento foi reduzido em 36,62% e no de 200 µm a redução foi de 3,29%. Os resultados mostram a importância da simulação para prever a tendência do empenamento, quando existe a necessidade de muitas variações de parâmetros de processo de fabricação. / The development of new technologies of semiconductors packaging has reduced the size of the tracks of printed circuit boards in search of miniaturization. This reduction has been reaching its own possible limits (of construction) because it has several problems, such as increase of resistance, rupture by electromigration, in addition to the increase of costs of particles control in manufacturing cleanrooms. Package on Package (PoP) comes as a proposition for encapsulation with thin chips piling in order to reduce chip occupation on the board. The difference in thermal and mechanical properties of the different materials that make up the encapsulated chip may result in the warpage of the component. In this study, the thermomechanical behavior of an electronic device encapsulated by the Package on Package technology was simulated. From the thermal and mechanical point of view, it was evaluated what factors cause the warpage of the semiconductors encapsulated with the PoP technology, warpage which is recurrent in the molding process. The manufacturing process conditions and parameters were assessed/evaluated during the making of a 40μm-thick chip prototype which was molded with a type 2 Epoxi Molding Compound - EMC - in the Materials Laboratory of Hongik University Department of Materials Science and Engineering in South Korea, our partner in this research project. Through the warpage measurements, by Moiré interferometry carried out in South Korean Hana Micron's test laboratory, we managed to build correlations with the computing simulation of this component. The results of this comparison were used as base for validation of the simulation and for adjustment of input data used in three different thickness of silicon chips (70, 100 and 200 μm) and two different EMC (EMC1 and EMC2). The manufacturing process conditions and parameters, the influence in warpage of different thicknesses and simulated components EMC types were evaluated. The simulations carried out with EMC variation in components with 40μm chip demonstrated that type 1 EMC has a decrease in warpage of the upper part of the component (Top) 42.39 percent larger than type 2 EMC. On the Top, the substract plus chip with 100 μm thickness, the warpage was reduced in 36.62 percent, and in the 200 μm chip, the reduction was by 3.29 percent. The results show the importance of simulation to predict warpage tendency, when there is the need for many variations of manufacturing production parameters.

La batterie lithium ion est la technologie de stockage d’énergie la plus répandue dans l'industrie automobile. Assurer sa haute efficacité, sa puissance, sa capacité, sa sécurité et son endurance présente un défi pour plusieurs chercheurs et industriels. En effet, une batterie est un système complexe renfermant plusieurs composants et soumis à divers risques de dégradations d’origines chimiques, mécaniques et électriques, se manifestant même dans les conditions normales de fonctionnement. Cependant, la batterie devrait assurer ses fonctions pour un grand nombre de cycles de charge et de décharge et continuer à servir sans que ces dégradations influencent sa performance globale. L’une des dégradations principales et inévitables est son gonflement qui induit une discontinuité électrique et une perte de sa capacité.En effet, le gonflement est un phénomène multi-physique qui fait intervenir l’électrochimie, la mécanique et la thermique. D’une part, une batterie lithium-ion est basée sur l’échange réversible de l’ion lithium entre une électrode positive et une électrode négative. Le processus d’insertion de l’ion dans les particules de l’électrode aboutit à un changement volumique significatif réversible de la batterie pour chaque cycle de charge/décharge. Cette variation de volume mène à la formation de contraintes quand la batterie est maintenue dans un pack rigide empêchant ou limitant sa déformation. D’autre part, la formation d’une couche à l’interface particule-électrolyte (SEI) suite aux réactions parasites se produisant à l’échelle de l’électrode constitue une cause principale d’un gonflement supplémentaire irréversible et de vieillissement de la batterie.Ainsi, le gonflement doit être pris en compte pendant la phase du dimensionnement mécanique de la batterie. Il est donc indispensable d’avoir un outil numérique fiable capable de prédire ce comportement mécanique pendant toutes les phases de fonctionnement de la batterie et de permettre aux concepteurs d’améliorer sa structure.Ce travail rentre dans le cadre d’une collaboration entre l’ENSTA ParisTech et le constructeur automobile Renault suite à un besoin industriel de comprendre et de maîtriser le gonflement des batteries utilisées dans les véhicules électriques et hybrides. Pour répondre à ce besoin, un modèle multi-physique et multi-échelle fondé sur la théorie de la thermodynamique des processus irréversibles, sur l’endommagement et sur la théorie de l’homogénéisation est développé. Il permet de décrire et de prédire la déformation d’une batterie lithium ion pendant son fonctionnement. Le modèle tient compte des phénomènes mécaniques, électrochimiques et thermiques qui se produisent à l’échelle locale des électrodes afin de calculer la déformation mécanique au niveau macroscopique de la batterie. / Lithium ion battery is the most popular energy storage technology in the automotive industry. Ensuring high efficiency, power, capacity, safety and endurance is a challenge for many researchers and manufacturers. Indeed, a battery is a complex system containing several components and subject to various risks of chemical, mechanical and electrical damage, manifesting even under normal operating conditions. However, the battery should perform its functions for a large number of charge and discharge cycles and continue to serve without these risks influencing its overall performance. One of the main and inevitable damage is its swelling, which induces an electrical discontinuity and a loss of its capacity.Indeed, swelling is a multi-physics phenomenon that involves electrochemistry, mechanics and heat. On the one hand, a lithium-ion battery is based on the reversible exchange of the lithium ion between a positive electrode and a negative electrode. The process of inserting the ion into the particles of the electrode results in a significant reversible volume change of the battery for each charge / discharge cycle. This variation in volume leads to the formation of stresses when the battery is held in a rigid pack preventing or limiting its deformation. On the other hand, the formation of a layer at the particle-electrolyte interface (SEI) following parasitic reactions occurring at the electrode scale is a major cause of irreversible additional swelling and aging of the drums.Thus, the swelling must be taken into account during the mechanical sizing phase of the battery. It is therefore essential to have a reliable numerical tool able to predict this mechanical behavior during all phases of battery operation and to allow designers to improve its structure.This work is part of a collaboration between ENSTA ParisTech and the car manufacturer Renault following an industrial need to understand and control the swelling of batteries used in electric and hybrid vehicles. To meet this need, a multi-physics and multi-scale model based on the theory of the thermodynamics of irreversible processes, mechanical damage theory and the homogenization theory is developed. It allows to describe and predict the deformation of a lithium ion battery during its operation. The model takes into account the mechanical, electrochemical and thermal phenomena that occur at the local scale of the electrodes in order to calculate the mechanical deformation at the macroscopic level of the battery.