O objetivo do presente trabalho é o desenvolvimento de formulações e de códigos computacionais que possibilitem a análise bidimensional estática de meios contínuos anisotrópicos viscoplásticos reforçados ou não por fibras. Especificamente, as análises numéricas envolvem aplicações dos métodos dos elementos de contorno (MEC) e dos elementos finitos (MEF), comparando-se os resultados obtidos com respostas analíticas e experimentais, disponíveis na literatura, buscando-se assim, subsídios teóricos que permitam o entendimento de problemas mais gerais envolvendo meios anisotrópicos. Para tanto são empregados elementos finitos triangulares com aproximações cúbica e quadrática para os deslocamentos na modelagem dos domínios. Na consideração do reforço com fibras, elementos finitos de barras simples são empregados. A formulação desenvolvida proporciona também a consideração de distribuição randômica das fibras imersas no meio sem qualquer aumento dos graus de liberdade do problema analisado, diferindo-se assim, das formulações conhecidas até o momento. Com o MEC, a análise de plasticidade e viscoplasticidade em meios com anisotropia geral é feita de maneira original no trabalho, destacando-se a consideração de lei de fluxo plástico não-associativa e o tratamento de viscosidade apenas com integrais de contorno, sem a utilização de aproximações de domínio. Uma quantidade significativa de exemplos é apresentada, possibilitando a verificação da eficiência das formulações e dos códigos desenvolvidos / The objective of the present work is the development of formulations and computational codes that enable the static bidimensional analysis of the viscoplastic anisotropic medias reinforced, or not, by fibers. Specifically, the numerical analysis involve applications of the boundary elements method (BEM) and finite elements (FEM), comparing the results obtained with analytical and experimental solutions available in the literature, allowing the understanding of general problems in anisotropic media. Two-dimensional finite elements with cubic and quadrate approximations for the displacements are used to model domains. Reinforcements are modeled by truss finite elements. The developed formulation provides the consideration of random distribution of the fibers, without any additional degree of freedom of the problem. With the BEM, the plasticity and viscoplasticity analysis in general anisotropic medias is originally developed in the present work, emphasizing the consideration of non-associative plastic flow and the treatment of viscosity just with boundary integrals, without domain approximation. Various examples are shown in order to verify the efficiency of the proposed formulation and developed computational codes

Orientador: Laercio Carvalho de Barros. / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica. / Made available in DSpace on 2018-08-12T00:22:47Z (GMT). No. of bitstreams: 1 Missio_Maristela_D.pdf: 2748963 bytes, checksum: f8fcd60a906d00c35ee8f90f26919908 (MD5) Previous issue date: 2008 / Resumo: A febre aftosa é uma patologia viral, infecto-contagiosa, caracterizada por um cenário repleto de incertezas que lhe são inerentes, resultantes da influência de fatores socioeconômicos e ambientais relacionados ao processo de transmissão, que pode ocorrer por via direta e indireta. Em epidemiologia, grande parte das incertezas são tratadas ou pela Teoria das Probabilidades ou pela Teoria de Conjuntos Fuzzy, a depender da natureza, seja ela oriunda da aleatoriedade ou de verdade parcial. O uso integrado de modelos clássicos, particularmente as Equações Diferenciais Parciais (EDP), modelos fuzzy e probabilísticos no tratamento das duas classes de incertezas ainda é muito incipiente. Com a intenção de contribuir para o aumento dos estudos nessa área, propõe-se um modelo integrado, envolvendo EDP, lógica fuzzy e métodos probabilísticos, a fim de estudar a dinâmica espacial e temporal de fenômenos epidemiológicos, cujas incertezas são importantes para sua evolução. Para tanto, tomou-se como objeto de estudo a febre aftosa em bovinos e elaborou-se um modelo SIR envolvendo EDP para estudar sua evolução espaço-temporal com parâmetros de difusão e transmissão incertos. Esses foram estimados fazendo-se uso de Sistemas Baseados em Regras Fuzzy (SBRF). As variáveis lingüísticas utilizadas nos SBRF apresentaram incertezas de natureza aleatória, as quais foram tratadas por modelos estocásticos. Na implementação computacional, fez-se o acoplamento dos métodos de elementos finitos para a discretização espacial, e Cranck-Nicolson para a temporal, toolbox fuzzy para os modelos fuzzy e Monte Carlo para os modelos estocásticos, todos em um mesmo algoritmo, construído nos ambientes Matlab e Fortran. / Abstract: The foot-and-mouth disease is a viral, infectum contagious pathology, characterized for a scene full of inherent uncertainties, resultants of the influence of social, economic and environmental factors related to the transmission process, that can occur for direct and indirect means. In Epidemiology, great part of the uncertainties are treated either by the Theory of Probabilities or by Fuzzy Logic Theory, depending on the nature, in accordance with the type of uncertainty which can be either deriving of the randomness or coming from the subjectivity. The integrated use of models involving Partial Differential Equations (PDE), Fuzzy Theory and Probabilistic in the treatment of the two categories of uncertainties, simultaneously, is still very incipient. Aiming to contribute to the growth of existing studies in this area, we propose an integrated model, involving PDE Models, Fuzzy Models and Stochastic Models, in order to study the space and secular dynamics of these epidemiological phenomena, whose uncertainties are important for their evolution. To do so, the foot-and-mouth disease in bovines was taken overcome as our study's object and we elaborated a SIR model involving EDP to study its space-weather evolution with uncertain parameters of diffusion and transmission. Due the uncertainties these parameters had been estimated using Rule-Based Fuzzy Systems (RBFS). The linguistic variables of the RBFSs presented uncertainties of random nature, which were treated by random models. For computational results, we coupling several models, using the method of finite elements for the space discretization and Cranck-Nicolson for time discretization, toolbox fuzzy for Fuzzy Models and Mount Carlo for Random Models, all in the same algorithm constructed in the environments Matlab and Fortran. / Doutorado / Matematica Aplicada / Doutor em Matemática Aplicada

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-04-18T13:51:58Z No. of bitstreams: 1 marcusviniciusdesouzaferraz.pdf: 4103901 bytes, checksum: e4adcd64380c6ba8941b29bcc9d0abfd (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-04-19T17:48:41Z (GMT) No. of bitstreams: 1 marcusviniciusdesouzaferraz.pdf: 4103901 bytes, checksum: e4adcd64380c6ba8941b29bcc9d0abfd (MD5) / Made available in DSpace on 2018-04-19T17:48:41Z (GMT). No. of bitstreams: 1 marcusviniciusdesouzaferraz.pdf: 4103901 bytes, checksum: e4adcd64380c6ba8941b29bcc9d0abfd (MD5) Previous issue date: 2018-02-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O conhecimento da topografia das superfícies e uma compreensão da interação entre elas é essencial para qualquer estudo que envolva os fenômenos de atrito, desgaste e lubrificação. O estudo da relação entre o atrito e os parâmetros de rugosidade é um problema difícil e de interesse tanto industrial como acadêmico e trabalhos experimentais e teóricos têm mostrado que uma película de fluido entre duas superfícies rugosas em movimento relativo impede o contato sólido - sólido e pode proporcionar atrito muito baixo e desgaste desprezível. A modelagem matemática utilizada neste trabalho é baseada em modelos clássicos, tais como a equação de Reynolds para a descrição dos fenômenos hidrodinâmicos e as formulações de Hertz (1896) e Greenwood e Williamson (1966) para a modelagem do contato das asperezas entre as superfícies rugosas. Para tratar a complexidade das interações entre o fluido e os pares sólidos contactados, a descrição Lagrangiana-Euleriana Arbitrária é apresentada nesta pesquisa. Através do Método dos Elementos Finitos um modelo tridimensional é gerado no Abaqus ®, a fim de identificar as pressões de contato, as tensões tangenciais e normais resultantes e os coeficientes de atrito decorrrentes do deslizamento entre uma superfície texturizada e lubrificada e um plano rígido (em analogia aos modelos de contato clássicos), cujos perfis de rugosidade são construídos a partir de informações da rugosidade média quadrática de superfícies dentárias. São avaliados também a sensibilidade de alguns parâmetros do lubrificante na determinação do coeficiente de atrito e são propostos modelos com condições de contorno distintas. Entretanto, para a verificação destes últimos busca-se reproduzir qualitativamente o resultado encontrado por Lorentz (2013) na investigação numérica de sistemas tribológicos no regime misto de lubrificação. A metodologia aqui proposta emerge como uma alternativa eficaz no campo da Tribologia, na predição do coeficiente de atrito e outras variáveis pertinentes a um fenômeno ainda pouco compreendido. Realiza-se uma análise de sensibilidade dos parâmetros de modelagem, a fim de identificar como os mesmos afetam consideravelmente o comportamento mecânico na interface de contato. / The knowledge of the topography of surfaces and an understanding of the interaction between them is essential for any study involving the phenomena of friction, wear and lubrication. The study of the relationship between friction and roughness parameters is a difficult problem of both industrial and academic interest and experimental and theoretical works have shown that a fluid film between two rough surfaces in relative motion prevents solid - solid contact and can provide very low friction and negligible wear. The mathematical modeling used in this paper is based on classical models, such as the Reynolds equation for the description of the hydrodynamic phenomena and the formulations of Hertz (1896) and Greenwood e Williamson (1966) of the contact between the asperities of rough surfaces. To address the complexity of the interactions between the fluid and the contacted solid pairs, the Lagrangian-Eulerian Arbitrary description is presented in this research. Through the Finite Element Method, a three-dimensional model is generated in Abaqus ®R to identify contact pressures, resulting tangential and normal stresses, and friction coefficients resulting from sliding between a textured and lubricated surface and a rigid plane (in analogy to classic contact models), whose roughness profiles are constructed from information on the quadratic roughness of dental surfaces. The sensitivity of some lubricant parameters in the determination of the coefficient of friction is also evaluated and models with different boundary conditions are proposed. However, for the vefrification of the latter, it is sought to qualitatively reproduce the result found by Lorentz (2013) in the numerical investigation of tribological systems without mixed lubrication regime. A methodology proposed here emerges as an effective alternative in the field of Tribology, in the prediction of the coefficient of friction and other relevant variables to a phenomenon still little understood. A sensitivity analysis of the modeling parameters is performed, in order to identify how they considerably affect the mechanical behavior at the contact interface.

En zone de montagne, les avalanches de neige menacent les personnes et également les structures de génie civil. Ce travail de thèse se focalise sur une structure de protection en BA (Béton Armé) de type mur en L. L'objectif est de caler et valider un modèle EF (Elément Fini) 2D afin d'étudier le comportement de tels ouvrages sous l'effet de champs de pression induits par des avalanches de neige dense et d'évaluer leur vulnérabilité face à cet aléa naturel. Quatre lois de comportement décrivant la rhéologie du béton ont été testées en vue de reproduire le plus précisément possible la ruine du mur en BA. Un modèle physique de la structure à échelle 1/6 a permis, via un test pushover, d'obtenir des données expérimentales utiles pour le calage des modèles EF proposés. Seulement deux des lois de comportement ont permis de converger vers un mode de ruine pertinent et en accord avec les observations expérimentales. Le modèle EF une fois calé a ensuite été utilisé afin d'investiguer la réponse mécanique de l'ouvrage sous sollicitation avalancheuse. En fonction de l'impulsion du signal de chargement, trois régimes peuvent être obtenus (quasi-statique, dynamique et impulsionnel). Dans le cas d'une avalanche de neige dense, les résultats montrent que la réponse mécanique de la structure en question peut être considérée comme quasi-statique. Toutefois, les signaux avalancheux dépendant de nombreux facteurs (type d'avalanche, densité, température, etc.), différents types de réponses peuvent potentiellement se développer. Pour finir, la vulnérabilité et la fiabilité du mur en BA ont été étudiées afin de préciser l'influence d'une part de la géométrie et d'autre part des caractéristiques des matériaux sur la capacité de protection qu'offre ce type d'ouvrage. In fine, ces résultats pourront être utilisés dans un cadre de gestion intégrée du risque. / Snow avalanches threaten people and also different types of civil engineering structures in mountainous areas. This PhD thesis focuses on a protective RC (Reinforced Concrete) structure consisting of an L-shaped wall. The objective of this study is to calibrate and validate a 2D FE (Finite Element) model in order to explore the mechanical behavior of such RC structures loaded by snow avalanche pressure fields and to assess their vulnerability when exposed to this kind of natural hazard. Four constitutive laws describing the concrete rheology were tested to describe the collapse of the RC wall. A physical 1/6-scale model permitted obtaining, via a pushover test, useful experimental data for the calibration of the proposed FE models. Two concrete models allowed converging to a relevant collapse of the structure in agreement with the experimental observations. Then, the calibrated FE model was used to investigate the mechanical response of the wall under avalanche loading. According to the impulse of the loading signal, three regimes can occur (quasi-static, dynamic or impulsive). In the case of dense-snow avalanches, the results show that the mechanical response of this structure can be described as quasi-static. However, avalanche signals depend on many factors (type of avalanche, density, temperature, etc.) and several types of responses can potentially develop. Finally, the vulnerability and the reliability of the RC wall were studied to show the influence of the geometry and the material properties on the capacity of the protective structure. In fine, these results will be used in an integrated risk framework in order to help decision makers.

The purpose of this thesis is to construct a numerically solvable quantum mechanical model describing the dynamics of the indirect mechanism of the dissociative recombination process of a molecular cation by electron impact. The model also describes vibrational excitation of a molecular cation by electron impact. The solution of this model is carried out by implementing a combination of finite elements, discrete variable representation and exterior complex scaling methods. This is then specifically applied to the dissociative recombination and vibrational excitation of H$_2^+$ by an incoming electron. The results can be used to test the accuracy of approximative methods and the programs expanded to cover the cases of other diatomics. Powered by TCPDF (www.tcpdf.org)

Eines der am häufigsten in der Automobilindustrie eingesetzten mechanischen Fügeverfahren ist das Clinchen, auch Durchsetzfügen genannt. Hierbei werden zwei oder mehr sich überlappende Bleche lokal umgeformt, sodass eine form- und kraftschlüssige Verbindung mit matrizenseitiger Überhöhung entsteht. Eine Sonderform des Clinchens ist das Flach-Clinchen zur Herstellung einseitig ebener Clinch-Verbindungen. Mit dem Ziel, die Verfahrensgrenzen des konventionellen Flach-Clinchens zu erweitern, werden im Rahmen der vorliegenden Arbeit zwei neuartige Verfahrensvarianten des Flach-Clinchens entwickelt. Um die Verbindungsfestigkeit der Flach-Clinch-Verbindung zu erhöhen, wird ein zusätzliches Hilfsfügeelement in den Fügepunkt eingebracht. Dies bewirkt zum einen eine Vergrößerung des Hinterschnittes und daraus resultierend eine erhöhte Belastbarkeit gegenüber Kopfzugbeanspruchung. Zum anderen wird der Fügepunkt durch das zusätzliche Material stabilisiert und folglich die Belastbarkeit gegenüber Scherzugbeanspruchung verbessert. Die zweite Verfahrensvariante beinhaltet die Kombination aus Flach-Clinchen und Kleben zum sogenannten Flach-Clinchkleben. Hierbei dient die mechanische Verbindung hauptsächlich als Fixierhilfe bis zur vollständigen Aushärtung des Klebstoffs. Dies ermöglicht eine direkte Weiterverarbeitung des Bauteils nach dem Fügen und somit eine deutliche Verkürzung der Prozesszeiten. Die Entwicklung des Flach-Clinchens mit Hilfsfügeelement und des Flach-Clinchklebens erfolgt ausschließlich mittels numerischer Simulationen. Die hierbei gewonnenen Erkenntnisse werden anschließend experimentell verifiziert und die Verbindungsfestigkeiten der neuentwickelten Verfahrensvarianten bestimmt. / Clinching is one of the most common used mechanical joining processes in automotive industry. Here, two or more overlapping metal sheets are locally formed so that a form- and force-closed joint with diesided protrusion is established. A special type of clinching is the so-called flat-clinching for the production of one-sided planar joints. Within the framework of this thesis, two novel process variants of flat-clinching are developed for enhancing the process limitations of conventional flat-clinching. For increasing the joint strength, a complementary joining element is inserted into the joint. This causes an enlargement of the interlocking, leading to a higher resistance to cross tension loads. Also, the additional material stabilizes the joint and hence improves the resistance to shear load. The second process variant, adhesive flat-clinching, includes the combination of flat-clinching and adhesive bonding. The metal sheets are fixed by flat-clinching and the final joint strength is achieved after the complete curing of the adhesive. This enables a continuous processing of the component and therefore, the process time can be shortened. The development of flat-clinching using complementary joining elements and adhesive flat-clinching is exclusively carried out by using numerical simulation. The knowledge gained from the simulations is subsequently experimentally proven. Also, the joint strength of the novel process variants is experimentally determined.

Lorsqu'une onde acoustique se propage dans un milieu granulaire, elle est susceptible de provoquer la mobilité des grains, aussi infime soit-elle. Inversement, la mobilité d'un grain dans une matrice fluide peut induire un champ acoustique et dans les deux cas, l'énergie acoustique peut être transférée à la fois au travers des pores et des contacts entre grains. Nous avons mis au point un modèle original permettant de considérer ces deux modes de transfert d'énergie pour simuler la propagation d'ondes acoustiques dans les milieux granulaires immergés. Dans le cas des milieux granulaires secs, l'inertie du fluide est telle que l'énergie transférée dans l'air peut être négligée et le milieu modélisé avec des algorithmes de type "dynamique moléculaire". Au contraire, dans le cas de milieux immergés, l'énergie portée par le fluide ne peut pas être négligée et nous montrons que la méthode des domaines fictifs basée sur les multiplicateurs de Lagrange distribués permet de coupler les équations de la dynamique et l'équation d'onde. Nous utilisons la méthode des éléments finis pour propager l'onde dans le fluide, les grains étant modélisés en 2D par des sphères rigides et incompressibles afin de satisfaire les hypothèses de l'algorithme de dynamique moléculaire. Les résultats du modèle sur des expériences numériques simples mais pour lesquelles existent des solutions analytiques de l'acoustique mettent en évidence la validité du nouveau modèle. Nous en donnons une illustration pour l'étude des interactions subies par un empilement réaliste de multiples grains mobiles soumis à un signal acoustique. / When an acoustic wave propagates through a granular medium, it causes the grains to move, usually very slightly. In the same way, the movement of a grain embedded in a fluid matrix generates an acoustic wave. In both cases, acoustic energy is transmitted by the fluid and by the inter-granular contacts. We have developed a new numerical model for simulating wave propagation in submerged granular media that takes into account these two modes of energy transport. For the case of dry granular media, the grains are embedded in air whose inertia is so low that the energy it carries can be neglected. These media can be modeled with "Molecular Dynamics" or related methods. On the contrary, when granular media are submerged in water, the energy carried by the fluid cannot be neglected, rendering their modelization much more difficult. We use the fictitious domain method with distributed Lagrange multipliers to couple the equation of motion of the grains to the wave equation of the fluid. We use finite elements to propagate the wave in the fluid, and the grains are modeled in 2D by rigid, incompressible spheres compatible with the hypotheses of Molecular Dynamics. To validate the model, we perform series of numerical experiments whose results are compared to analytic solutions from acoustics. We also perform a simulation with hundreds of grains under an incident wave to demonstrate the possibilities of the model.

Cette thèse s’inscrit dans le cadre des études des phénomènes électromagnétiques dansles régions frontales des grands turbo-générateurs. L’objectif de la thèse est d’estimer apriori le champ magnétique axial en fonction du point de fonctionnement afin d’éviterles possibles dégradations du circuit magnétique (dus aux points chauds et tensions entretôles, qui sont liés à la composante axiale du champ).Une maquette à échelle réelle a été spécialement conçue et réalisée dans le but d’améliorerla compréhension physique des phénomènes : les pertes, la pénétration du champ magnétiqueet les tensions entre tôles sont analysés.Les simulations par éléments finis sont ensuite utilisées : les avantages et inconvénientsseront discutés, ainsi qu’une comparaison critique des résultats par rapport aux mesuresexpérimentales sur la maquette. La région frontale d’un turbo-alternateur est aussi entièrementmodélisée.Enfin, un modèle simple du flux axial est développé. Ses coefficients sont déterminés àl’aide de simulations par éléments finis, mais il peut ensuite être utilisé en temps réel afind’estimer le flux axial correspondant à un point de fonctionnement quelconque. / This work aims to improve the knowledge of electromagnetic phenomena that occurin the end region of large turbo-generators. The goal of this work is to evaluate theaxial magnetic flux density with regard to the operating conditions (such as active orreactive power) in order to prevent potential deterioration of the stator. Indeed, the axialmagnetic field is known to induce hot points or voltages between laminations that maycause insulation breakdown and thus stator faults.An experimental apparatus in real scale has been designed and built. Its purpose is tostudy precisely the following phenomena: losses, axial magnetic flux density penetration,voltage across adjacent voltages.Finite element simulations (FEM) are also used: their advantages and drawbacks arediscussed, and the results are compared with the experimental measures. The wholeend-region of a turbo-generator is also simulated.Finally, a simple model of the axial magnetic flux is proposed. Its parameters are basedon the results of the FEM model, but it may be used in real time to evaluate the axialmagnetic flux density of any operating point.

This master thesis deals with optimization of the shape of the stator and rotor slots of induction motor with focusing on increasing efficiency. The theoretical part introduces the principles of optimization algorithms. Another part is devoted to design the shape of slots and its influence on the shape of slots on machine. On the models of motor was conducted the optimized shape of slots by using a genetic algorithm. Firstly, it was performed by using the analytical calculation in the RMxprt program, then by using the finite element method on two different models, whose difference simulates the influence of the production technology on the efficiency of the motor. Laboratory measurement was made on a real machine as well. The results of the measurement, calculations and optimizations are compared in the work.

This thesis deals with gradient calculation in triangulation nodes using weighted average of gradients of neighboring elements. This gradient is then used for a posteriori error estimation which produce better solution of partial differential equations. This work presents two common methods - Finite elements method and Finite difference method.