In this thesis a theory for large deformation of plates is presented. Herein aspects of the common 3D-theory for large deformation with the Kirchhoff hypothesis for reducing the dimension from 3D to 2D is combined. Even though the Kirchhoff assumption was developed for small strain and linear material laws, the deformation of thin plates made of isotropic non-linear material was investigated in a numerical experiment. Finally a heavily deformed shell without any change in thickness arises. This way of modeling leads to a two-dimensional strain tensor essentially depending on the first two fundamental forms of the deformed mid surface. Minimizing the resulting deformation energy one ends up with a nonlinear equation system defining the unknown displacement vector U. The aim of this thesis was to apply the incremental Newton technique with a conformal, C^1-continuous finite element discretization. For this the computation of the second derivative of the energy functional is the key difficulty and the most time consuming part of the algorithm. The practicability and fast convergence are demonstrated by different numerical experiments.

This thesis investigates the numerical simulation of three-dimensional, mechanical deformation problems in the context of large deformations. The main focus lies on the prediction of non-linearly elastic, incompressible material. Based on the equilibrium of forces, we present the weak formulation of the large deformation problem. The discrete version can be derived by using linearisation techniques and an adaptive mixed finite element method. This problem turns out to be a saddle point problem that can, among other methods, be solved via the Bramble-Pasciak conjugate gradient method or the minimal residual algorithm. With some modifications the resulting simulation can be improved but we also address remaining limitations. Some numerical examples show the capability of the final FEM software. In addition, we briefly discuss the special case of linear elasticity with small deformations. Here we directly derive a linear weak formulation with a saddle point structure and apply the adaptive mixed finite element method. It is shown that the presented findings can also be used to treat the nearly incompressible case.

La manipulation dextre est un sujet important dans la recherche en robotique et dans lequel peu de travaux ont abordé la manipulation d'objets déformables. De nouvelles applications en chirurgie, en industrie agroalimentaire ou encore dans les services à la personne nécessitent la maîtrise de la saisie et la manipulation d'objets déformables. Cette thèse s’intéresse à la manipulation d’objets déformables par des préhenseurs mécaniques anthropomorphiques tels que des mains articulées à plusieurs doigts. Cette tâche requière une grande expertise en modélisation mécanique et en commande : modélisation des interactions, perception tactile et par vision, contrôle des mouvements des doigts en position et en force pour assurer la stabilité de la saisie. Les travaux présentés dans cette thèse se focalisent sur la modélisation de la saisie d'objets déformables. Pour cela, nous avons utilisé une discrétisation par des systèmes masses-ressorts non-linéaires pour modéliser des corps déformables en grands déplacements et déformations tout en ayant un coût calculatoire faible. Afin de prédire les forces d’interactions entre main robotique et objet déformable, nous avons proposé une approche originale basée sur un modèle rhéologique visco-élasto-plastique pour évaluer les forces tangentielles de contact et décrire la transition entre les modes d’adhérence et de glissement. Les forces de contact sont évaluées aux points nodaux en fonction des mouvements relatifs entre les bouts des doigts et les facettes du maillage de la surface de l’objet manipulé. Une autre contribution de cette thèse consiste à utiliser de cette modélisation dans la planification des tâches de manipulation d’objets déformables 3D. Cette planification consiste à déterminer la configuration optimale de la main pour la saisie de l’objet ainsi que les trajectoires à suivre et les efforts à appliquer par les doigts pour contrôler la déformation de l’objet tout en assurant la stabilité de l’opération. La validation expérimentale de ces travaux a été réalisée sur deux plateformes robotiques : une main Barrett embarquée sur un bras manipulateur Adept S1700D et une main Shadow embarquée sur un bras manipulateur Kuka LWR4+. / Dexterous manipulation is an important issue in robotics research in which few works have tackled deformable object manipulation. New applications in surgery, food industry or in service robotics require mastering the grasping and manipulation of deformable objects. This thesis focuses on deformable object manipulation by anthropomorphic mechanical graspers such as multi-fingered articulated hands. This task requires a great expertise in mechanical modeling and control: interaction modeling, tactile and vision perception, force / position control of finger movements to ensure stable grasping. The work presented in this thesis focuses on modeling the grasping of deformable objects. To this end, we used a discretization by non-linear mass-spring systems to model deformable bodies in large displacements and deformations while having a low computational cost. To predict the interaction forces between robot hand and deformable object, we proposed an original approach based on a visco-elasto-plastic rheological model to evaluate tangential contact forces and describe the transition between the sticking and slipping modes. The contact forces are evaluated at nodes as function of the relative movements between the fingertips and the surface mesh facets of the manipulated object. Another contribution of this thesis is the use of this model in the planning of 3D deformable object manipulation tasks. This planning consists in determining the optimal configuration of the hand for grasping the objects as well as the paths to track and the efforts to be applied by the fingers to control the deformation of the object while ensuring the stability of the operation. The experimental validation of this work has been carried out on two robotic platforms: a Barrett hand embedded on a Adept S1700D ® manipulator and a Shadow hand embedded on a Kuka LWR4+® manipulator.

In the simulation of deformations of plates it is well known that we have to use a special treatment of the thickness dependence. Therewith we achieve a reduction of dimension from 3D to 2D. For linear elasticity and small deformations several techniques are well established to handle the reduction of dimension and achieve acceptable numerical results. In the case of large deformations of plates with non-linear material behaviour there exist different problems. For example the analytical integration over the thickness of the plate is not possible due to the non-linearities arising from the material law and the large deformations themselves. There are several possibilities to introduce a hypothesis for the treatment of the plate thickness from the strong Kirchhoff assumption on one hand up to some hierarchical approaches on the other hand.:1. Introduction 2. The 3D-deformation energy 3. Basic differential geometry of shells 4. Kirchhoff assumption and the deformed plate 5. Plate energy and boundary conditions 6. Numerical example

No description available.

This thesis investigates the numerical simulation of three-dimensional, mechanical deformation problems in the context of large deformations. The main focus lies on the prediction of non-linearly elastic, incompressible material. Based on the equilibrium of forces, we present the weak formulation of the large deformation problem. The discrete version can be derived by using linearisation techniques and an adaptive mixed finite element method. This problem turns out to be a saddle point problem that can, among other methods, be solved via the Bramble-Pasciak conjugate gradient method or the minimal residual algorithm. With some modifications the resulting simulation can be improved but we also address remaining limitations. Some numerical examples show the capability of the final FEM software. In addition, we briefly discuss the special case of linear elasticity with small deformations. Here we directly derive a linear weak formulation with a saddle point structure and apply the adaptive mixed finite element method. It is shown that the presented findings can also be used to treat the nearly incompressible case.

No / Solid phase orientation of polymers is one of the most successful routes to enhancement of polymer properties. It unlocks the potential of molecular orientation for the achievement of a range of enhanced physical properties. We provide here an overview of techniques developed in our laboratories for structuring polymers by solid phase orientation processing routes, with a particular focus on die drawing, which have allowed control of significant enhancements of a single property or combinations of properties, including Young's modulus, strength, and density. These have led to notable commercial exploitations, and examples of load bearing low density materials and shape memory materials are discussed.

Thin and slender structures are widely occurring both in nature and in human creations. Clever geometries of thin structures can produce strong constructions while using a minimal amount of material. Computer modeling and analysis of thin and slender structures has its own set of problems stemming from assumptions made when deriving the equations modeling their behavior from the theory of continuum mechanics. In this thesis we consider two kinds of thin elastic structures; threads and plates. Real-time simulation of threads are of interest in various types of virtual simulations such as surgery simulation for instance. In the first paper of this thesis we develop a thread model for use in interactive applications. By viewing the thread as a continuum rather than a truly one dimensional object existing in three dimensional space we derive a thread model that naturally handles both bending, torsion and inertial effects. We apply a corotational framework to simulate large deformation in real-time. On the fly adaptive resolution is used to minimize corotational artifacts. Plates are flat elastic structures only allowing deflection in the normal direction. In the second paper in this thesis we propose a family of finite elements for approximating solutions to the Kirchhoff-Love plate equation using a continuous piecewise linear deflection field. We reconstruct a discontinuous piecewise quadratic deflection field which is applied in a discontinuous Galerkin method. Given a criterion on the reconstruction operator we prove a priori estimates in energy and L2 norms. Numerical results for the method using three possible reconstructions are presented.

Este trabalho propõe estudar o projeto de estruturas submetidas a grandes deslocamentos utilizando o Método de Otimização Topológica (MOT). O MOT é um método numérico capaz de fornecer de forma sistemática a distribuição ótima de material no domínio de uma estrutura de forma a atender a um dado requisito de projeto, por exemplo, o valor de flexibilidade máxima permitida em uma estrutura. Desde sua introdução, há quase três décadas, o MOT ganhou popularidade na área acadêmica e na indústria. Até o presente momento (2011), a maioria dos trabalhos relacionados com o método tem se preocupado com a otimização de estruturas com o comportamento linear, ou seja, pequenos deslocamentos. Um pequeno número de artigos e trabalhos tem sido relacionado com a modelagem e otimização topológica de estruturas submetidas a efeitos não-lineares. Este trabalho propõe compilar as formulações descritas na literatura e agregar novas técnicas na implementação da OT de forma a melhorar a robustez na obtenção de resultados sob não-linearidade geométrica. O MOT para o comportamento não-linear geométrico neste trabalho foi implementado utilizando o modelo de material SIMP. O comportamento não-linear geométrico é representado utilizando a formulação Lagrangiana para as leis de material de Kirchhoff-Saint Venant e neo-Hookiana. Ambas as leis de material foram implementadas utilizando o método de elementos finitos (MEF) e o equilíbrio estático da estrutura é obtido através de uma rotina incremental e iterativa de Newton incluindo todos os elementos (inclusive os de baixa densidade) dentro do domínio de projeto. A sensibilidade da função objetivo é deduzida utilizando o método adjunto e o problema de otimização é resolvido utilizando o Método das Assíntotas Móveis (MAM) em conjunto com uma função de Relaxação proposta para estabilizar a solução de OT não-linear. A função de projeção não-linear em conjunto com o Método da Continuação é utilizada para eliminar o problema de tabuleiro e independência de malha, melhorando a convergência dos resultados. A função objetivo para minimização da flexibilidade no ponto de aplicação do carregamento é testada, considerando um carregamento fixo. Neste trabalho, os exemplos mostram que as diferenças na rigidez das estruturas otimizadas utilizando modelagem linear e não-linear são geralmente pequenas para pequenos carregamentos, mas elas podem ser grandes em certos casos envolvendo grandes cargas, acarretando em instabilidades na estrutura, o que pode degenerar a solução obtida. / This work proposes studying the design of structures undergoing large displacement using Topology Optimization Method (TOM). The TOM is a numerical method capable of synthesizing the basic layout of a mechanical structure accomplishing to a given design requirement, for example the maximum strain energy allowed in the structure. Since its introduction nearly three decades, TOM has gained widespread popularity in academia and industry. So far, most papers dealing with the method have been concerned with the optimization of structures with linear geometric and material behavior. Even now a small number of works and articles have been concerned with the modeling and topology optimization of structures undergoing nonlinear effects. This work proposes to compile the formulations described in the literature and adding new techniques to improve the robustness for obtaining results of OT under geometric nonlinearity. The TOM for geometric nonlinear behavior in this work is implemented with Solid Isotropic Microstructure with Penalization (SIMP) material model. The geometrically nonlinear behavior of the structures is modeled using a Lagrangean description for hyperelastic constitutive models for Saint Venant-Kirchhoff and neo-Hookean. Both constitutive models are implemented using the Finite Element Method (FEM) and the static equilibrium of the structure is obtained using an incremental and iterative Full-Newton Method considering all elements and internal force of the design domain (elements called \"voids\"). The sensitivity of the objective function is derived using the adjoint method and the optimization problem is solved using the Optimality Criteria (OC) method and Method of Moving Asymptotes (MMA) together with a Relaxation Function proposed to stabilize the TO nonlinear solution. The nonlinear projection function in conjunction with the Continuation Method is used to obtain checkerboard-free and mesh-independent designs and to improve the convergence results. The objective function of end-compliance is tested, by minimizing it for a fixed load. In this work, some examples show that differences in stiffness of optimized structures using linear and nonlinear modeling are generally small, however they can be large in certain cases involving buckling or bifurcation point, that degenerate the solution obtained.

Este trabalho propõe estudar o projeto de estruturas submetidas a grandes deslocamentos utilizando o Método de Otimização Topológica (MOT). O MOT é um método numérico capaz de fornecer de forma sistemática a distribuição ótima de material no domínio de uma estrutura de forma a atender a um dado requisito de projeto, por exemplo, o valor de flexibilidade máxima permitida em uma estrutura. Desde sua introdução, há quase três décadas, o MOT ganhou popularidade na área acadêmica e na indústria. Até o presente momento (2011), a maioria dos trabalhos relacionados com o método tem se preocupado com a otimização de estruturas com o comportamento linear, ou seja, pequenos deslocamentos. Um pequeno número de artigos e trabalhos tem sido relacionado com a modelagem e otimização topológica de estruturas submetidas a efeitos não-lineares. Este trabalho propõe compilar as formulações descritas na literatura e agregar novas técnicas na implementação da OT de forma a melhorar a robustez na obtenção de resultados sob não-linearidade geométrica. O MOT para o comportamento não-linear geométrico neste trabalho foi implementado utilizando o modelo de material SIMP. O comportamento não-linear geométrico é representado utilizando a formulação Lagrangiana para as leis de material de Kirchhoff-Saint Venant e neo-Hookiana. Ambas as leis de material foram implementadas utilizando o método de elementos finitos (MEF) e o equilíbrio estático da estrutura é obtido através de uma rotina incremental e iterativa de Newton incluindo todos os elementos (inclusive os de baixa densidade) dentro do domínio de projeto. A sensibilidade da função objetivo é deduzida utilizando o método adjunto e o problema de otimização é resolvido utilizando o Método das Assíntotas Móveis (MAM) em conjunto com uma função de Relaxação proposta para estabilizar a solução de OT não-linear. A função de projeção não-linear em conjunto com o Método da Continuação é utilizada para eliminar o problema de tabuleiro e independência de malha, melhorando a convergência dos resultados. A função objetivo para minimização da flexibilidade no ponto de aplicação do carregamento é testada, considerando um carregamento fixo. Neste trabalho, os exemplos mostram que as diferenças na rigidez das estruturas otimizadas utilizando modelagem linear e não-linear são geralmente pequenas para pequenos carregamentos, mas elas podem ser grandes em certos casos envolvendo grandes cargas, acarretando em instabilidades na estrutura, o que pode degenerar a solução obtida. / This work proposes studying the design of structures undergoing large displacement using Topology Optimization Method (TOM). The TOM is a numerical method capable of synthesizing the basic layout of a mechanical structure accomplishing to a given design requirement, for example the maximum strain energy allowed in the structure. Since its introduction nearly three decades, TOM has gained widespread popularity in academia and industry. So far, most papers dealing with the method have been concerned with the optimization of structures with linear geometric and material behavior. Even now a small number of works and articles have been concerned with the modeling and topology optimization of structures undergoing nonlinear effects. This work proposes to compile the formulations described in the literature and adding new techniques to improve the robustness for obtaining results of OT under geometric nonlinearity. The TOM for geometric nonlinear behavior in this work is implemented with Solid Isotropic Microstructure with Penalization (SIMP) material model. The geometrically nonlinear behavior of the structures is modeled using a Lagrangean description for hyperelastic constitutive models for Saint Venant-Kirchhoff and neo-Hookean. Both constitutive models are implemented using the Finite Element Method (FEM) and the static equilibrium of the structure is obtained using an incremental and iterative Full-Newton Method considering all elements and internal force of the design domain (elements called \"voids\"). The sensitivity of the objective function is derived using the adjoint method and the optimization problem is solved using the Optimality Criteria (OC) method and Method of Moving Asymptotes (MMA) together with a Relaxation Function proposed to stabilize the TO nonlinear solution. The nonlinear projection function in conjunction with the Continuation Method is used to obtain checkerboard-free and mesh-independent designs and to improve the convergence results. The objective function of end-compliance is tested, by minimizing it for a fixed load. In this work, some examples show that differences in stiffness of optimized structures using linear and nonlinear modeling are generally small, however they can be large in certain cases involving buckling or bifurcation point, that degenerate the solution obtained.