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Rückert, Jens, and Arnd Meyer. "Kirchhoff Plates and Large Deformation." Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-96896.
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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.
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Crabbé, Blandine. "Gradient damage models in large deformation." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX085/document.
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Les modèles d'endommagement à gradient, aussi dénommés modèles à champs de phases, sont désormais largement utilisés pour modéliser la rupture fragile et ductile, depuis l'initiation de l'endommagement jusqu'à la propagation d'une fissure. Cependant, la majorité des études disponibles dans la littérature ne concerne que le cadre des petites déformations, et très peu d'études poussées ont été menées afin d'étudier leur pertinence dans un contexte de grandes déformations. Ce serait pourtant d'un intérêt primordial, notamment pour l'industrie pneumatique, qui deviendrait alors capable de prédire plus précisément l'initiation de l'endommagement dans ses structures.Dans la première partie de ce travail, nous établissons des solutions analytiques d'évolution de l'endommagement (homogène et localisée) pour des matériaux visqueux, en petites et en grandes déformations. En petites déformations, les modèles rhéologiques de Maxwell et Poynting-Thomson sont étudiés, et en grandes déformations, les modèles de Maxwell et Zener sont choisis. Une étude sur l'évolution de l'endommagement dans un cas purement hyperélastique est aussi menée.A cette première partie analytique succède une partie numérique, qui détaille l'implémentation des modèles d'endommagement à gradient dans des codes éléments finis en grandes déformations. De même qu'en petites déformations, une stratégie de minimisation alternée est adoptée pour résoudre successivement les problèmes d'endommagement et de déplacement. Le matériau suit une loi de Mooney-Rivlin quasi-incompressible, et une méthode mixte en déplacement-pression est utilisée. Des tests en 2D et 3D sont effectués, qui mettent en évidence la capacité des modèles à initier de l'endommagement en grandes déformations.Les modèles d'endommagement utilisés pour la seconde partie ne sont cependant capables d'initier de l'endommagement que dans les zones où la déformation est importante, c'est-à-dire dans les zones de forte contrainte déviatorique. Il a toutefois été montré que certains matériaux polymères, quasi-incompressibles, s'endommagent dans les zones de forte pression hydrostatique. Par conséquent, la recherche et l'étude d'un modèle d'endommagement capable d'initier de l'endommagement dans les zones de forte pression, pour des matériaux quasi-incompressibles lorsqu'ils sont sains, fait l'objet d'une troisième partie.Enfin, la croissance brusque de cavités dans un matériau hyperélastique, appelée phénomène de cavitation, est étudiée, ainsi que son interaction avec l'endommagement. Dans un premier temps, nous considérons la cavitation comme une simple bifurcation hyperélastique d'un matériau néo-hookéen compressible isotrope, et déterminons l'expression analytique de l'élongation critique pour laquelle la cavitation fait son apparition. Dans un second temps, nous montrons qu'il y a une compétition entre la cavitation et l'endommagement, et qu'en fonction de la valeur du ratio des élongations critiques respectives pour chaque phénomène, deux types de rupture apparaissent<br>Gradient damage models, also known as phase-field models, are now widely used to model brittle and ductile fracture, from the onset of damage to the propagation of a crack in various materials. Yet, they have been mainly studied in the framework of small deformation, and very few studies aims at proving their relevance in a finite deformation framework. This would be more helpful for the tyre industry that deals with very large deformation problems, and has to gain insight into the prediction of the initiation of damage in its structures.The first part of this work places emphasis on finding analytical solutions to unidimensional problems of damaging viscous materials in small and large deformation.In all the cases, the evolution of damage is studied, both in the homogeneous and localised cases. Having such solutions gives a suitable basis to implement these models and validate the numerical results.A numerical part naturally follows the first one, that details the specificities of the numerical implementation of these non local models in large deformation. In order to solve the displacement and damage problems, the strategy of alternate minimisation (or staggered algorithm) is used. When solved on the reference configuration, the damage problem is the same as in small deformation, and consists in a bound constraint minimisation. The displacement problem is non linear, and a mixed finite element method is used to solve a displacement-pressure problem. A quasi-incompressible Mooney-Rivlin law is used to model the behaviour of the hyperelastic material. Various tests in 2D and 3D are performed to show that gradient damage models are perfectly able to initiate damage in sound, quasi-incompressible structures, in large deformation.In the simulations depicted above, it should be noted that the damage laws combined to the hyperelastic potential results in an initiation of damage that takes place in zones of high deformation, or in other words, in zones of high deviatoric stress. However, in some polymer materials, that are known to be quasi-incompressible, it has been shown that the initiation of damage can take place in zones of high hydrostatic pressure. This is why an important aspect of the work consists in establishing a damage law such that the material be incompressible when there is no damage, and the pressure play a role in the damage criterion. Such a model is exposed in the third part.Finally, the last part focuses on the cavitation phenomenon, that can be understood as the sudden growth of a cavity. We first study it as a purely hyperelastic bifurcation, in order to get the analytical value of the critical elongation for which cavitation occurs, in the case of a compressible isotropic neo-hookean material submitted to a radial displacement. We show that there is a competition between the cavitation phenomenon and the damage, and that depending on the ratio of the critical elongation for damage and the critical elongation for cavitation, different rupture patterns can appear
3
Boyce, Mary Cunningham. "Large inelastic deformation of glassy polymers." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14909.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987.<br>MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING<br>Bibliography: leaves 126-130.<br>by Mary Cunningham Boyce.<br>Ph.D.
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Paradinas, Salsón Teresa. "Simplification, approximation and deformation of large models." Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/51293.
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The high level of realism and interaction in many computer graphic applications requires techniques for processing complex geometric models. First, we present a method that provides an accurate low-resolution approximation from a multi-chart textured model that guarantees geometric fidelity and correct preservation of the appearance attributes. Then, we introduce a mesh structure called Compact Model that approximates dense triangular meshes while preserving sharp features, allowing adaptive reconstructions and supporting textured models. Next, we design a new space deformation technique called *Cages based on a multi-level system of cages that preserves the smoothness of the mesh between neighbouring cages and is extremely versatile, allowing the use of heterogeneous sets of coordinates and different levels of deformation. Finally, we propose a hybrid method that allows to apply any deformation technique on large models obtaining high quality results with a reduced memory footprint and a high performance.<br>L’elevat nivell de realisme i d’interacció requerit en múltiples aplicacions gràfiques fa que siguin necessàries tècniques pel processament de models geomètrics complexes. En primer lloc, presentem un mètode de simplificació que proporciona una aproximació precisa de baixa resolució d'un model texturat que garanteix fidelitat geomètrica i una correcta preservació de l’aparença. A continuació, introduïm el Compact Model, una nova estructura de dades que permet aproximar malles triangulars denses preservant els trets més distintius del model, permetent reconstruccions adaptatives i suportant models texturats. Seguidament, hem dissenyat *Cages, un esquema de deformació basat en un sistema de caixes multi-nivell que conserva la suavitat de la malla entre caixes veïnes i és extremadament versàtil, permetent l'ús de conjunts heterogenis de coordenades i diferents nivells de deformació. Finalment, proposem un mètode híbrid que permet aplicar qualsevol tècnica de deformació sobre models complexes obtenint resultats d’alta qualitat amb una memòria reduïda i un alt rendiment.
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Tuzun, Aydin. "Large Deformation Analysis Of Flexible Multibody Systems." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614821/index.pdf.
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Large displacement and large strain problems of mechanical systems can be solved mainly by four methods. These are Floating Frame of Reference, Incremental Finite Element, Large Rotation Vector and Absolute Nodal Coordinate Formulations (ANCF). Due to exact rigid body representation, simple mass matrix structure and non-incremental formulation, ANCF is more convenient in analyzing flexible multibody systems. However, it is limited to problems with regular boundaries, currently.
The aim of the thesis is to improve the current ANCF in order to handle various problems with irregular boundaries. For this purpose, firstly meshfree ANCF has been developed to analyze flexible multibody systems. Verification of the developed meshfree formulation has been performed for beam type structures and accurate results have been obtained. Then, &ldquo<br>ANCF with Virtual Element Mapping Method&rdquo<br>has been proposed to overcome the boundary problems of the current formulations. The proposed method has been implemented to plane stress, plane strain, plate/shell and 3D solid finite elements. Verification of the proposed method has been performed by using the patch test problems available in the literature. Besides, it has been verified by various flexible multibody problems with large deformations. Additionally, shape function polynomials for thin plate assumption have been derived.
It is observed that developed formulations and methods can be useful not only for flexible multibody systems but also for structural mechanics problems subjected to large deformations and/or rotations. The proposed methods and formulations are more efficient than the current formulations in the literature due to extended shape limits of finite elements.
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Derian, Edward J. "Large deformation dynamic bending of composite beams." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45678.
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</p>The large deformation response of composite beams subjected to a
dynamic axial load was studied. The beams were loaded with a moderate
amount of eccentricity to promote bending. The study was primarily
experimental but some finite element results were obtained. Both the
deformation and the failure of the beams were of interest. The static
response of the beams was also studied in order to determine the
difference between the static and dynamic failure. Twelve different
laminate types were tested. The beams tested were 23 in. by 2 in. and
generally 30 plies thick. The beams were loaded dynamically with a
gravity-driven impactor traveling at 19.6 ft./sec. and quasi-static
tests were done on identical beams in a displacement controlled
manner. For laminates of practical interest, the failure modes under
static and dynamic loadings were identical. Failure in most of the
laminate types occurred in a single event involving 40% to 50% of the
plies. However, failure in laminates with 30° or 15° off axis plies occurred in several events. All laminates exhibited bimodular
properties. The compressive flexural moduli in some laminates was
measured to be 1/2 the tensile flexural modulus. No simple relationship
could be found among the measured ultimate failure strains of the
different laminate types. Using empirically determined flexural
properties, a finite element analysis was reasonably accurate in
predicting the static and dynamic deformation response.</p><br>Master of Science
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Weise, Martina. "Elastic Incompressibility and Large Deformations." Doctoral thesis, Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-140113.
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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.
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Evcim, Mehmet. "Large Deformation Analysis Of Shells Under Impulsive Loading." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611647/index.pdf.
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In this thesis large deformation behavior of shell structures under high intensity transient loading conditions is investigated by means of finite element method. For this purpose an explicit finite element program is developed with interactive user interface. The developed program deals with geometric and material nonlinearities which stem from large deformation elastic - plastic behavior.
Results of the developed code are compared with the experimental data taken from the literature and simulation results of the commercial finite element program Ls-Dyna. Moreover, sensitivity study is carried out for mesh size, element type and material model parameters. After the comparison and verification of the obtained results, it is concluded that converged and reasonable results are achieved.
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Ma, Jianfeng. "Meshless method for modeling large deformation with elastoplasticity." Diss., Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/402.
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RIOS, GABRIEL EMILIANO BARRIENTOS. "NONLINEAR DYNAMICS OF FLEXIBLE STRUCTURES WITH LARGE DEFORMATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19770@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>É apresentado o modelo não-linear de barras proposto por Simo para o estudo do comportamento dinâmico de estruturas espaciais. A formulação das equações do movimento é feita em um sistema inercial de modo a simplificar o operador de inércia e o material é considerado como elástico linear. Carregamos não – conservativos são considerados de modo que a integração das equações é feita na forma fraca. As partes flexíveis, que são necessariamente estruturas unidimensionais, são descritas por um modelo de barras que generaliza os modelos clássicos de Euler-Bernouilli e de Timoshenko. Implementa-se um programa computacional baseado nesta teoria na linguagem Matlab. O modelo de barras discretiza-se espacialmente usando elementos finitos e integra-se o sistema de equações resultante linearizado usando o método de Newton-Raphson, associado ao esquema de integração de Newmark. Incorpora-se os efeitos de amortecimento interno e cargas seguidoras, assim como elementos lineares quadráticos. Se incorpora à programação o tratamento de juntas esféricas através do método de multiplicadores de Lagrange, que permitem estudar alguns tipos de sistemas de multicorpos flexíveis. O programa é testadopor uma série de exemplos e comparações com resultados clássicos para mostrar a sua versatilidade e também as limitações dos modelos clássicos. Também se apresenta o modelo usado no programa computacional SAMCEF, e mostra-se a potencialidade deste programa em base a uma série de exemplos que incluem problemas de flexibilidade e choque em sistemas multicorpos.<br>It is presented a theory to treat multibody problems with rigid or flexible parts that treats the overall motion and the deformations in the same way using na inertial reference frame.
The essential part of the model is the treatment of nonlinear rods that are flexible parts of the multibody systems.
A code was construcetd in the platform MATBLAB and it was widely tested thorough comparisons with results found in the literature that acted as benchmark problems. The results are very good.
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Brown, Rebecca A. (Rebecca Ann) 1976. "Large strain deformation of PETG as processing temperatures." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88847.
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Eterovic, Adrian Luis. "Finite element analysis of large deformation contact problems." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13063.
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Abu-Saman, Awni. "Large plastic deformation and shear localization of crystals." Doctoral thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/4954.
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Derisi, Bijan. "Development of thermoplastic composite tubes for large deformation." Thesis, Connect to online version, 2008. http://proquest.umi.com/pqdweb?did=1675143241&sid=1&Fmt=2&clientId=10306&RQT=309&VName=PQD.
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Wan, Deborah Jo-May 1974. "On elastic-plastic large deformation analysis of beams." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10076.
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Hallett, N. M. "Large displacement deformation of plates subject to projectile impact." Thesis, City University London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379616.
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Lei, Fulin. "Modeling of articular cartilage optimization, large deformation, and microstructure /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 1.21 Mb., 176 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3220728.
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Michael, Detlef, and Mathias Meisel. "Some remarks to large deformation elasto-plasticity (continuum formulation)." Universitätsbibliothek Chemnitz, 2005. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200501150.
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The continuum theory of large deformation elasto-plasticity is summarized as far as it is necessary for the numerical treatment with the Finite-Element-Method. Using the calculus of modern differential geometry and functional analysis, the fundamental equations are derived and the proof of most of them is shortly outlined. It was not our aim to give a contribution to the development of the theory, rather to show the theoretical background and the assumptions to be made in state of the art elasto-plasticity.
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Cheung, Chip. "Large deformation of textile fabrics using finite element method." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182782321.
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Weldon, James P. (James Peter). "The deformation of large telescope mirrors and optical quality." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41428.
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Honeker, Christian. "Large strain deformation behavior of oriented triblock copolymer cylinders." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10430.
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Rehermann, Pablo F. Sanz. "Modeling rock folding with large deformation frictional contact mechanics /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Parsons, Ethan M. (Ethan Moore) 1972. "Mechanics of large-strain deformation of particle-modified polymers." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37048.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.<br>Includes bibliographical references (p. 267-274).<br>Over the past several decades, engineering polymers have become increasingly prevalent in the manufacture of virtually all types of products. Polymers are substantially less dense than metals, easy to machine, and readily formed into quite complex geometries. The properties of polymers may be altered by the introduction of second-phase particles. Typically, soft, rubber particles are added to increase fracture toughness while rigid, mineral particles are added to reduce costs or to increase stiffness, thermostability, or porosity. The deformation to large strains of particle-modified thermoplastic polymers is investigated. Blends with rubber particles and blends with calcium carbonate particles are considered. A novel experimental technique is utilized to characterize the three-dimensional deformation of polycarbonate blends and high-density polyethylene blends during uniaxial tension tests. True stress, true strain, volumetric strain, and full-field contours of strain are extracted from images of the deforming specimens. The experimental results are used to construct and verify single-particle and multi-particle micromechanical models.<br>(cont.) In the micromechanical models, the stress triaxiality ratio and the properties of the particles, matrix, and interfaces are varied in order to determine their effects on local and macroscopic deformation. A constitutive model for polymers with perfectly bonded or debonding rigid particles is developed based on the knowledge gained from the experiments and micromechanical models.<br>by Ethan Moore Parsons.<br>Ph.D.
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Smiri, Jalal. "Large plastic deformation of crystals : stability analysis and attractors." Electronic Thesis or Diss., Paris 13, 2024. http://www.theses.fr/2024PA131052.
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Cette thèse porte sur l'utilisation de modèles de plasticité cristalline (PC) pour étudier l'évolution microstructurale des matériaux mono- et polycristallins soumis à des conditions de chargement extrêmes associées à de grandes déformations. La plasticité cristalline constitue un outil puissant pour modéliser les interactions de dislocations, la rotation du réseau cristallin, la croissance des cavités et les effets de taille, offrant ainsi une meilleure compréhension des mécanismes de déformation critiques tels que la localisation des déformations, la formation de bandes de cisaillement et l'évolution des cavités. En adoptant une approche eulérienne, ce travail surmonte les difficultés liées à la distorsion de maillage rencontrées dans les méthodes traditionnelles, permettant des simulations précises des grandes déformations. Des simulations à haute résolution en plasticité cristalline, rendues possibles grâce à une technique de remaillage, sont utilisées pour explorer le rôle des attracteurs de densité de dislocations et d'orientation du réseau cristallin, ainsi que les mécanismes derrière la croissance et l'évolution des formes des cavités lors de la déformation.La prédiction des attracteurs d'orientations cristallines dans les processus de déformation pilotés par le gradient de vitesse est cruciale pour comprendre la texture finale d'un polycristal. Nous avons réalisé une analyse de stabilité sur un problème simplifié (2D avec trois systèmes de glissement) afin de développer une stratégie théorique capable de prédire les attracteurs d'orientations cristallines à grande déformation. Deux simulations numériques illustrent cette théorie : la déformation d'un polycristal sous un chargement de gradient de vitesse homogène et l'évolution d'une cavité dans un monocristal sous un gradient de vitesse non homogène.Nous avons développé une analyse de stabilité pour les processus pilotés par les taux de glissement pour certains modèles établis basés sur la densité de dislocations, y compris le modèle de Kocks et Mecking (KM) et ses variantes, afin d'identifier les conditions menant à des états stationnaires dans les systèmes de glissement actifs et d'évaluer leur stabilité linéaire. Notre analyse peut être généralisée à tout type de modèle de densité de dislocations, fournissant ainsi un cadre plus large pour comprendre la stabilité de ces systèmes. Il est intéressant de noter qu'à partir d'un modèle qui ne considère pas les effets d'échelle, nous révélons des effets dépendants de la taille se manifestant à travers des variations initiales de la densité de dislocations, en particulier dans les échantillons préparés par FIB, influençant les réponses d'affaiblissement ou de durcissement des matériaux. Des simulations numériques de compression de micro piliers ont été réalisées pour aborder le comportement des matériaux à des dimensions nano/micrométriques. Les mécanismes de croissance et de coalescence des cavités sont des facteurs clés dans la rupture ductile des matériaux cristallins, se produisant à travers un écoulement plastique important autour de cavités préexistantes ou de cavités nucléées sur des particules de seconde phase. L'objectif principal est d'analyser la croissance de cavités plates dans des monocristaux (HCP, FCC) en utilisant des simulations par éléments finis en plasticité cristalline avec une déformation eulérienne pour mieux comprendre la croissance des cavités. Le modèle proposé permet non seulement de capturer le début de l'écoulement plastique, mais aussi de prédire avec précision l'évolution des formes des cavités. Le modèle est appliqué à des études expérimentales ayant observé qu'une cavité initialement circulaire dans un cristal HCP évolue vers une cavité polyédrique sous un chargement radial<br>This thesis focuses on employing Crystal Plasticity (CP) models to study the microstructural evolution in mono- and polycrystalline materials under extreme loading conditions associtaed with large deformations. CP provides a powerful tool to model dislocation interactions, lattice rotation, void growth, and size-dependent effects, offering insights into critical deformation mechanisms such as strain localization, shear band formation, and void evolution. By adopting an Eulerian framework, this work overcomes the challenges of mesh distortion in traditional methods, allowing accurate simulations of large deformations. High-resolution CP simulations achieved through a re-meshing technique, are used to explore the role of dislocation density and lattice orientation attractors, as well as the mechanisms behind void growth and shape evolution during deformation. The prediction of attractors for lattice orientations in velocity gradient process is of great interest in understating the final texture of a poly-crystal. We have done a stability analysis of a simpler problem (2-D with 3 slip systems) in order to developed a theoretical strategy able to predict the lattice orientations attractors for large strains. Two numerical simulations illustrate the theory: deformation of a poly-crystal under a homogeneous velocity gradient loading and the void evolution of a mono-crystal under a non-homogeneous velocity gradient loading. We have developed a stability analysis of slip rate driven processes for some established dislocation density-based models, including the Kocks and Mecking (KM) model and its variants, aiming to identify conditions for stationary states in active slip systems and evaluate their linear stability. Our analysis can be generalized to any type of dislocation density model, providing a broader framework for understanding the stability of such systems. Interestingly, from a size independent model we uncover size-dependent effects manifesting through initial dislocation density variations, particularly in FIB-prepared samples, influencing the material's softening or hardening responses. Some numerical simulations of micro-pillar compression have been performed to address the behavior of materials at nano-scale dimensions. The mechanisms of void growth and coalescence are key contributors to the ductile failure of crystalline materials, occurring through large plastic flow around pre-existing voids or nucleated cavities at second-phase particles. The main goal is to analyze growth of flat voids in single crystals (HCP, FCC) using Eulerian deformation crystal plasticity finite element simulations to better understand the void growth. The proposed model not only captures the onset of yielding but also accurately predicts the evolution of void shapes. The model is applied to experimental studies, which observed that an initially circular void in an HCP crystal evolves into a polyhedral cavity in a radial loading. Two processes are studied: radial loading applied on a hexagonal close-packed (HCP) crystal, and tensile loading on a face-centered cubic (FCC) crystal. These cases illustrate the model's capability in different crystallographic structures and loading conditions, thereby demonstrating its broader applicability. Finally, we derive some formulas for calculating true stress in cases where slip/kink bands form during mechanical loading in compression experiments on pillars. Specifically, we consider a localization, observed frequently in experiments as single band oriented in arbitrary directions with respect to the vertical axis of the pillar, for which we derive a formula and employ it to assess the reliability of previous experimental results
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Barnhoorn, Auke. "Rheological and microstructural evolution of carbonate rocks during large strain torsion experiments /." [Zurich] : [s.n.], 2003. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15309.
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Wung, Pey M. "Large deformation analysis of laminated composite structures by a continuum-based shell element with transverse deformation." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54815.
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In this work, a finite element formulation and associated computer program is developed for the transient large deformation analysis of laminated composite plate/shell structures. In order to satisfy the plate/shell surface traction boundary conditions and to have accurate stress description while maintaining the low cost of the analysis, a newly assumed displacement field theory is formulated by adding higher-order terms to the transverse displacement component of the first-order shear deformation theory. The laminated shell theory is formulated using the Updated Lagrangian description of a general continuum-based theory with assumptions on thickness deformation. The transverse deflection is approximated through the thickness by a quartic polynomial of the thickness coordinate. As a result both the plate/shell surface tractions (including nonzero tangential tractions and nonzero normal pressure) and the interlaminar shear stress continuity conditions at interfaces are satisfied simultaneously. Furthermore, the rotational degree of freedoms become layer dependent quantities and the laminate possesses a transverse deformation capability (i.e. the normal strain is no longer zero).
Analytical integration through the thickness direction is performed for both the linear analysis and the nonlinear analysis. Resultants of the stress integrations are expressed in terms of the laminate stacking sequence. Consequently, the laminate characteristics in the normal direction can be evaluated precisely and the cost of the overall analysis is reduced. The standard Newmark method and the modified Newton Raphson method are used for the solution of the nonlinear dynamic equilibrium equations.
Finally, a variety of numerical examples are presented to demonstrate the validity and efficiency of the finite element program developed herein.<br>Ph. D.
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Franke, Marlon [Verfasser]. "Discretisation techniques for large deformation computational contact elastodynamics / Marlon Franke." Karlsruhe : KIT Scientific Publishing, 2014. http://www.ksp.kit.edu.
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Cheng, Wan. "Large deformation nonlinear FEA and applications for metal forming processes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1995. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ42732.pdf.
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Hillmansen, Stuart. "Large strain bulk deformation and brittle tough transitions in polythene." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272493.
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Karamanou, Marianna. "A study of finite element modelling of large viscoelastic deformation." Thesis, Brunel University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415032.
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Orazalin, Zhandos Y. "Analysis of large deformation offshore geotechnical problems in soft clay." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111442.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 269-281).<br>Although finite element (FE) methods are well established for modeling geotechnical problems in soil masses and soil-structure interaction, most prior research on large deformation problems has been limited to simplified assumptions on drainage conditions and constitutive behavior. This thesis investigates two large deformation problems in soft clay and proposes a methodology for performing coupled flow and deformation analyses with advanced effective stress models. The first part of the research focuses on realistic 3-D finite element analyses (using AbaqusTM Standard) of a conductor (steel pipe pile) embedded within soft marine clay subjected to large lateral deformations caused by drift/drive-off of a drilling vessel. The proposed analyses use coupled pore pressure-displacement procedures together with the MIT-E3 soil model to represent the anisotropic, non-linear and inelastic effective stress-strain-strength properties of deepwater marine sediments with input parameters derived from a series of laboratory element tests performed on reconstituted Gulf of Mexico (GoM) clay. The numerical predictions are evaluated through comparison with experimental results from centrifuge tests with a well-instrumented model conductor. The FE results accurately predict the measured bending moment distribution along the length of the conductor and the spread of plastic strains within the conductor itself. The study has also shown the effects of soil behavior on local pile-soil interactions, enabling simplified analyses using macro-elements. The FE results have been used to calibrate input parameters for BWGG framework (Gerolymos & Gazetas, 2005), the Bouc-Wen (BW) model extended by Gerolymos and Gazetas (GG), that simulates generalized hysteretic pile-soil interactions and allows for degradation in soil resistance associated with geometric non-linearities. The second application considers the effects of partial drainage for large deformation, quasi-static piezocone penetration in clay. The proposed axisymmetric FE analysis procedure introduces automated remeshing and solution mapping technique (similar to RITSS; Hu & Randolph, 1998) within a commercial FE solver. We have analyzed the penetration resistance for a piezocone device using two elasto-plastic soil models (MCC, MIT-E3) and the recent elasto-viscoplastic MIT-SR soil model (Yuan, 2016) over a range of steady penetration velocities. The MCC predictions are in very good agreement with laboratory measurements of tip resistance and penetration pore pressures measured in centrifuge model tests in reconstituted kaolin. The results from more advanced soil models illustrate the impacts of anisotropic, rate dependent soil behavior on penetration tests in natural clays and are within the range of empirical measurements. The proposed analyses provide a complete framework that can now be used to investigate effects of partial drainage that occurs in piezocone tests for soils (such as silts) of intermediate permeability.<br>by Zhandos Y. Orazalin.<br>Ph. D.
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Talamini, Brandon Louis. "Simulation of deformation and fracture in very large shell structures." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103420.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 207-221).<br>Although advances in computing have increased the limits of three-dimensional computational solid mechanics, structural elements remain essential in the practical design of very large thin structures such as aircraft fuselages, ship hulls, automobiles, submarines, and pressure vessels. In many applications, fracture is a critical design concern, and thus the ability to numerically predict crack propagation in shells is a highly desirable goal. There are relatively few tools devoted to computational shell fracture, and of the existing approaches, there are two main defects: First, the existing methods are not scalable, in the sense of parallel computing, and consequently simulation of large structures remains out of reach. Second, while the existing approaches treat in-plane tensile failure, fracture due to transverse shearing has largely been ignored. In this thesis, a new computational framework for simulating deformation and fracture in large shell structures is presented that is well-suited to parallel computation. The scalability of the framework derives from the combination of a discontinuous Galerkin (DG) finite element method with an interface element-based cohesive zone representation of fracture. This representation of fracture permits arbitrary crack propagation, branching, and merging, without on-the-fly mesh topological changes. Furthermore, in parallel computing, this propagation algorithm is indifferent to processor boundaries. The adoption of a shear-flexible shell theory is identified as a necessary condition for modeling transverse shear failure, and the proposed method is formulated accordingly. Locking is always an issue that emerges in numerical analysis of shear-flexible shells; here, the inherent flexibility afforded by DG methods in the choice of approximation spaces is exploited to prevent locking naturally, without recourse to mixed methods or reduced integration. Hence, the DG discretization elegantly solves both the problems of scalability and locking simultaneously. A stress resultant-based cohesive zone theory is proposed that considers transverse shear, as well as bending and in-plane membrane forces. The theory is quite general, and the specification of particular constitutive relations, in the form of resultant traction-separation laws, is independent of the discretization scheme. Thus, the proposed framework should be extensible and useful for a variety of applications. A detailed description of the implementation strategy is provided, and numerical examples are presented which demonstrate the ability of the framework to capture all of the relevant modes of fracture in thin bodies. Finally, a numerical example of explosive decompression in a commercial airliner is shown as evidence that the proposed framework can successfully perform shell fracture simulations of unprecedented size.<br>by Brandon Louis Talamini.<br>Ph. D.
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Shan, Sicong. "Planar Soft Functional Periodic Structures Exploiting Instabilities and Large Deformation." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:23845411.
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Soft materials can significantly change their shape and volume when subjected to various stimuli.
Materials with deliberately designed periodic microstructure have long been proved to be characterized by properties that may exceed those of the corresponding bulk material. Though traditionally
avoided as modes of failure, mechanical instabilities have recently been exploited to design systems
with novel and tunable functionalities. Interestingly, the studies I conducted during my PhD show
that the combination of soft materials, periodic structures, mechanical instabilities and large deformation give us the opportunity to design materials and structures with enhanced functionality.
In this thesis, I present a systematic study on the response of planar sof୴ functional materials
which use their large deformation and geometric rearrangements to dramatically change their properties. In particular, I used a combination of experiments and numerical simulations to investigate
the effect of important parameters, such as pore shape, hole arrangement and loading conditions. With the fundamental understanding I gained, I developed a novel class of planar soft periodic
materials with enhanced material functionalities such as tunable phononic band-gap, spontaneous
symmetry breaking, chirality amplification and energy trapping. Remarkably, since the continuous
2D soft and porous structures I studied take advantage of reversible and scale-independent mechanisms, the proposed designs can be applied over a wide range of length scales.
The studies presented here show that by mastering the interplay between the microstructure of
soft periodic structures and their large deformation behavior, novel materials with enhanced func<br>Engineering and Applied Sciences - Engineering Sciences
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Chen, Tzung-Ming. "Synthesis of compliant single crystal silicon mechanisms with large deformation." Tönning Lübeck Marburg Der Andere Verl, 2009. http://d-nb.info/995862664/04.
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Paloumbi, Vassia Vasiliki. "Monitoring large strain deformation in the processing of polyethylene pipes." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497537.
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Hodge, Michael. "Development, deformation style, and seismic hazard of large normal faults." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/112226/.
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Young rifts such as the Malawi Rift System, located at the southern end of the East African Rift System, are a natural laboratory for how continents begin to break apart. Extension is typically accommodated by earthquakes within the upper crust. However, where extension occurs at a slow rate, the small number of historically recorded earthquakes likely provides an incomplete view of the potential magnitude range of events, limiting seismic hazard knowledge and the understanding of rift dynamics. Geological and geomorphological studies of faults scarps may help understand how faults develop, structurally evolve and accommodate displacement. Thus, in this thesis, using field and satellite observations of fault scarps, alongside numerical models, I develop a number of new methodologies in order to better understand young rift evolution. I show that the coseismic stress change between two active parallel faults influences whether the faults link, and the linkage style is determined by the distance between the faults. I also show that the orientation of a major border fault in a young rift can be influenced by local stresses and/or weakness at depth, forming faults oblique to what is expected by the regional stress field. Lastly, I identify segmentation on several Malawi Rift System faults from variations in scarp height and steps in the fault traces, and show that the morphology of each can be used to infer the number of prehistoric earthquake events. My work may suggest that large, normal faults in young rifts develop through a specific growth model, and that they can host earthquakes larger in magnitude than historically recorded. This research can help better understand rift evolution and earthquake hazard in the Malawi Rift System, as well as other regions where normal faults have the potential to cause large magnitude earthquakes, such as the Rukwa rift, Baikal rift and the Basin and Range Province.
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Bonatti, Colin. "Design and large deformation response of additively-manufactured shell-lattices." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121763.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 179-185).<br>Open-cell cellular solids are porous structures with a large variety of applications, from energy absorption to medical engineering. In an attempt to identify isotropic configurations with high low and large strain mechanical properties, detailed numerical simulations are conducted on a wide range of mesostructures of cubic symmetry. Results are partially validated through uniaxial compression of specimens made of 316L stainless steel via selective laser melting. In a first study the large deformation responses of four different mesostructures of relative density 20% are compared: an octet truss-lattice, tube-lattice, a sphere assembly and a tube/sphere hybrid. It is concluded that periodic shell structures provide superior strength and energy absorption capacity for the same weight, as compared to truss-lattices.<br>Another conclusion is that to avoid concentrations of plastic strains that are detrimental to the overall energy absorption of the structure, it is best to avoid peaks in curvature. Based on these conclusions, a shell-lattice is developed that resembles a smoothened Triply Periodic Minimal Surface of FCC symmetry. Its properties are compared to those of the octet-truss for a wide range of relative densities, revealing the shell-lattice as superior to the octet-truss in almost all cases. The FCC shell-lattice is then compared to its BCC and SC equivalents. It is found that the structures all present high anisotropic properties. For a given structure, directional difference factors of up to 4.1 in uniaxial stiffness, 2 in yield strength and 1.8 in specific energy absorption are observed. However the directional averages of their properties are very similar.<br>Irrespective of the specific type of cubic symmetry, the shell-lattices are remarkably stiff, strong and energy-specific type of cubic symmetry, the shell-lattices are remarkably stiff, strong and energy-absorbing, particularly at relative densities above 0.1. To address the problem of anisotropy, novel families of shell-lattices that contain the previous examples are proposed. Design maps are established and reveal that the elastic anisotropy of shell-lattices can be conveniently tailored. As a result, isotropic topologies are identified. The elastically-isotropic shell-lattices feature similar overall performance that their TPMS-like counterparts as well as a significantly reduced plastic anisotropy. The structures obtained are believed to be the best performing open-cell topologies to date.<br>Financially supported by the MIT Fracture Consortium and the Swiss National Foundation<br>by Colin Bonatti.<br>Ph. D.<br>Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Shao, Wei. "Identifying the shape collapse problem in large deformation image registration." Thesis, University of Iowa, 2016. https://ir.uiowa.edu/etd/2276.
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This thesis examines and identifies the problems of shape collapse in large deformation image registration. Shape collapse occurs in image registration when a region in the moving image is transformed into a set of near zero volume in the target image space. Shape collapse may occur when the moving image has a structure that is either missing or does not sufficiently overlap the corresponding structure in the target image. We state that shape collapse is a problem in image registration because it may lead to the following consequences: (1) Incorrect pointwise correspondence between different coordinate systems; (2) Incorrect automatic image segmentation; (3) Loss of functional signal. The above three disadvantages of registration with shape collapse are illustrated in detail using several examples with both real and phantom data. Shape collapse problem is common in image registration algorithms with large degrees of freedom such as many diffeomorphic image registration algorithms. This thesis proposes a shape collapse measurement algorithm to detect the regions of shape collapse after image registration in pairwise and group-wise registrations. We further compute the shape collapse for a whole population of pairwise transformations such as occurs when registering many images to a common atlas coordinate system. Experiments are presented using the SyN diffeomorphic image registration algorithm and diffeomorphic demons algorithm. We show that shape collapse exists in both of the two large deformation registration methods. We demonstrate how changing the input parameters to the SyN registration algorithm can mitigate the collapse image registration artifacts.
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Schwaiger, Hans Frederick. "An implementation of smoothed particle hydrodynamics for large deformation, history dependent geomaterials with applications to tectonic deformation /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/6807.
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Meyer, Arnd. "Grundgleichungen und adaptive Finite-Elemente-Simulation bei "Großen Deformationen"." Universitätsbibliothek Chemnitz, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200701960.
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Holsgrove, Stephen Clive. "Large deformation, large roation elasto-plastic shell analysis with particular application to tubular members and joints." Thesis, Kingston University, 1987. http://eprints.kingston.ac.uk/20511/.
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The ultimate strength assessment of steel tubular members is of the utmost importance to the design and maintenance of many structures including large offshore platforms. Ultimate strength assessments I using numerical solutions must model both nonlinear material and geometric behaviour. The latter must consider large displacements, very often large rotations, and possibly even large strains. These numerical solutions must be computationally efficient and be capable of running on generally available computer hardware, i.e. minicomputers. To achieve this efficiency, attention must be paid to programming considerations, and a new suite of data management modules has been developed and is described in this thesis, which minimise disk storage and speed program development. In addition, the structural modelling was carried out almost exclusively using the Semiiaaf thin shell element. The work described in this thesis considers most of the components which contribute to the numerical ultimate strength analysis of steel tubular members. Theoretically, attention has been focused in two areas, namely the geometric nonlinearity and the automatic solution of the resulting nonlinear equations. A detailed study has been carried out to understand fully the main methods of accounting for geometric nonlinearity from fundamentals of continuum mechanics. The study has considered both the Green-Lagrange and Logarithmic strain measures with a Total Lagrangian, Updated Lagrangian and Eulerian description of motion. These formulations have been included in the Semiiaaf shell element, firstly using a continuum mechanics based approach, and secondly using the more orthodox stress resultant approach. At all stages within the thesis attention is drawn to the effects of the approximations which have been made and their resulting limitations in the respective formulations. The solution of the nonlinear equations is also covered in detail using Newton-type algorithms coupled with line searches. The solution algorithms have been derived for a constrained environment where a modified version of the generalised arc-length constraint has been used. The inclusion of material nonlinearity has been well developed previously but has been included for completeness. To demonstrate the performance and limitations of the theory presented, several carefully chosen numerical examples have been included which include the analysis of tubular steel T and X joints connections and residual strength assessment of a dented pipeline riser. Where possible, results have been compared with experimental tests. The thesis concludes that for general engineering structures, the Total Lagrangian approach based on the stress resultant model gives good engineering results, even in the presence of moderately large rotations. Of the alternative formulations the Updated Lagrangian layered approach is probably the most effective for large rotations and small to moderate strains.
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Rückert, Jens. "Kirchhoff Plates and Large Deformations - Modelling and C^1-continuous Discretization." Doctoral thesis, Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-121275.
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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.
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Ssemakula, Hamzah. "Manufacturihng of heavy rings and large copper canisters by plastic deformation." Doctoral thesis, KTH, Production Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3682.
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<p>Plastic deformation processes transform material fromas-received state to products meeting certain requirements inproperties, microstructure and shape. To achieve thistransformation, the relationship between material response andprocess conditions should be understood. This is usuallycomplicated by the complex conditions describing the actualprocess. Numerous techniques including empirical, physical,analytical and numerical can be employed.</p><p>In this thesis, numerical technique supported by lab- andfull-scale experiments has been employed to analyse the formingparameters. The first part of the thesis is focused on the useof such parameters to predict occurrence of material poresduring manufacturing of bearing rings. The second part dealswith the influence of forming parameters on the grain sizeduring fabrication of large copper canisters for encapsulationof nuclear waste. The primary task has been to study with thehelp of commercial FE-codes the magnitude and distribution offorming parameters such as accumulated effective strain,temperature, instantaneous hydrostatic pressure and materialflow at different stages of the forming process. In the firstpart, two types of ring manufacturing routes, which result inpore free and pore loaded rings are studied and compared.Material elements located in different areas of the workpiecehave been traced throughout the process. Results of theaccumulated strain and instant hydrostatic pressure have beenanalysed and presented in pressure-strain space. Itsassumed that high hydrostatic pressures together with higheffective strains are favourable for pore closure. Area of theworkpiece with unfavourable parameters have been identified andcompared with ultrasonic test results. Good agreement has beenobtained. Based on the results of this analysis, a new conceptfor avoiding pores in manufacturing of yet heavier rings hasbeen presented. The concept proposes a lighter upsetting in theinitial stage of the process and a more efficient piercingwhich results in higher hydrostatic pressure and bigger andbetter distributed effective strain.</p><p>In the second part of the thesis, the influence of formingparameters such as effective strain and temperature on thefinal grain size of the product has been studied in laboratoryscale. As-cast billets of cylindrical shape were extruded atdifferent temperatures and reductions. It has been shown thatthe grain size in the final product should be small in order toenable ultrasonic tests and to guarantee resistance towardscreep and corrosion. Simulations for different materialelements located at different distances from the axis ofsymmetry of the initial cylindrical workpiece have been carriedout. In this way, the parameters describing the deformationhistory of the elements have been determined as functions oftime. Experimentally obtained pre- and post deformation grainsize in the corresponding locations of the material weredetermined. Its concluded that low temperature coupledwith high effective strain are conducive for obtaining a smallgrain size. Based on the beneficial conditions for extrusion ofcopper, a more detailed FE-analysis of a full-scale industrialprocess is carried out. A coarse-grained cast ingot of purecopper is heated and by upset forging formed into a cylinder,which is then punched into a hollow blank for subsequentextrusion. The blank is extruded over a mandrel through a45-degree semi-angle die. Accumulated effective strain andtemperatureas functions of the tubular wall thickness havebeen studied at five different locations along the tubularaxis. Forming load requirement as function of tool displacementfor each stage of the process has been determined. Strain andtemperature levels obtained have been related to the grain sizeinterval obtained in the earlier work. It has been concludedthat the levels reached are within the interval that ensures asmall grain size. A similar analysis has been carried out forforging of large copper lids and bottoms. Die designmodifications to improve the grain size in the lid and tooptimise the forging process with respect to forging load andmaterial yield have been proposed. A method requiring a smallforging load for fabrication of the lids has been analysed</p><p><b>Keywords:</b><i>Pores; grain size; low forging load; effective strain;temperature; hydrostatic pressure; extrusion; forging;canister; lid; rings</i></p>
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SHAHBODAGH, KHAN Babak. "Large Deformation Dynamic Analysis Method for Partially Saturated Elasto-Viscoplastic Soils." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/151955.
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Ferranto, Justin. "Experimental characterization and FEA simulation of hyperelastic membranes under large deformation." abstract and full text PDF (free order & download UNR users only), 2005. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1436029.
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Polzin, Thomas [Verfasser]. "Large deformation diffeomorphic metric mappings : theory, numerics, and applications / Thomas Polzin." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2018. http://d-nb.info/1168860741/34.
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di, Bari Vincenzo. "Large deformation and crystallisation properties of process optimised cocoa butter emulsions." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6305/.
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The objectives of the research presented in this thesis were: (1) optimise the processing conditions for the production of water-in-cocoa butter emulsions; (2) understand the role of water droplets on the large deformation behaviour and crystallisation properties of emulsified systems. Results showed that a scraped surface heat exchanger could be used to produce tempered emulsions with a small average droplet size (~3 µm). In all systems stability was provided by the emulsifier and fat crystals forming a network both in the bulk and at the interface of the water droplets. Characterisation of the large deformation properties of emulsions showed that the elastic behaviour remained constant at low aqueous phase percentages while the strength at fracture decreased. This result suggests that water droplets act as stress-concentrator elements, which is probably due to their partial sintering with the bulk network. Results of crystallisation experiments have shown that the effect of droplets on kinetics of crystallisation depends on the degree of supercooling: only at relatively high temperatures (15, 20 °C) the dispersed droplets increased the kinetics of crystallisation compared to bulk cocoa butter (CB). With respect to polymorphic evolution, emulsified systems evolved faster toward more stable forms than bulk CB at all temperatures.
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White, Charles Samuel. "A combined isotropic-kinematic hardening model for large deformation metal plasticity." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14400.
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Ambrosio, Jorge Alberto Cadete. "Elastic-plastic large deformation of flexible multibody systems in crash analysis." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185578.
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The problem of formulating and numerically solving the equations of motion of flexible multibody systems for application to structural impact is considered in this dissertation. As an alternative to experimental tests and to numerical procedures such as hybrid models and finite element methods, multibody dynamics contains the ingredients for efficient crash analysis of these problems provided that a proper description of the deformations of the system components is included. Based on the principles of continuum mechanics, updated and total Lagrangian formulations are used to derive the equations of motion for a flexible body. The finite element method is applied to these equations in order to obtain a numerical solution of the problem. It is shown that the use of convected coordinate systems not only simplifies the form of the flexible body equations of motion, but it also lowers the requirements for objectivity of the material law. A simpler form of the finite element equations of motion is obtained when a lumped mass formulation is used, and the nodal accelerations are expressed in a nonmoving reference frame. In this form, not only the geometric and material nonlinear behavior of the flexible body is accounted for, but also the inertial coupling between the gross motion and the distributed flexibility is preserved. A reduction on the number of coordinates describing the flexible body is achieved with the application of the Guyan condensation technique or the modal superposition method. For partially flexible bodies with a small deformable part, an efficient kinetostatic method is derived assuming that the deformable part is massless. The equations of motion of the complete multibody system are formulated in terms of joint coordinates. The necessary velocity transformations between the set of independent velocities and the dependent velocities are derived. Special emphasis is paid to the formulation of the constraint equations of kinematic joints involving flexible bodies. The dynamics of a truck rollover are studied in order to illustrate the efficiency of the developed methodology. Several simulations are performed using a general purpose multibody dynamics analysis code.
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Ceccato, Francesca. "Study of large deformation geomechanical problems with the Material Point Method." Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424697.
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The numerical simulation of real geomechanical problems often entails an high level of complexity; indeed they are often characterized by large deformations, soil-structure interaction and solid-fluid interaction.
Moreover, the constitutive behavior of soil is highly non-linear.
Landslides, dam failure, pile installation, and undrground excavation are typical examples of large deformation problems in which the interaction between solid a fluid phase as well as the contact between bodies are essential.
This thesis addresses the challenging issue of the numerical simulation of large deformation problems in geomechanics.
The standard lagrangian finite element methods are not well suited to treat extremely large deformations because of severe difficulties related with mesh distortions.
The need to overcome their drawbacks urged researchers to devote considerable effort to the development of more advanced computational techniques such as meshless methods and mesh based particle methods.
In this study, the Material Point Method (MPM), which is a mesh based particle method, is exploited to simulate large deformation problems in geomechanics.
The MPM simulates large displacements with Lagrangian material points (MP) moving through a fixed mesh.
The MP discretize the continuum body and carry all the information such as mass, velocity, acceleration, material properties, stress and strains, as well as external loads.
The mesh discretizes the domain where the body move through; it is used to solve the equations of motion, but it does not store any permanent information.
In undrained and drained conditions the presence of water can be simulated in a simplified way using the one-phase formulation.
However, in many cases the relative movement of the water respect to the soil skeleton must be taken into account, thus requiring the use of the two-phase formulation.
The contact between bodies is simulated with an algorithm specifically developed for the MPM at the beginning of the century.
This algorithm was originally formulated for the frictional contact. It extension to the adhesive contact is considered in this thesis, which is well suited to simulate soil-structure interaction in case of cohesive materials.
In this thesis typical geomechanical problems such as the collapse of a submerged slope and the simulation of cone penetration testing are considered.
Numerical results are successfully compared with experimental data thus confirming the capability of the MPM to simulate complex phenomena.<br>La simulazione numerica di molti problemi geotecnici è spesso caratterizzata da un elevato grado di complessità, infatti tipici fenomeni come frane, collasso di rilevati e installazione di pali necessitanto di tener conto delle grandi defromazioni del materiale, dell'accoppiamento meccanico tra fase solida e fase liquida e dell'interazione terreno-struttura.
Questa tesi si occupa della simulazione numerica di tali problemi attraverso il Material Point Method, in particolare vengono considerati il collasso di un pendio sommerso e la penetrazione del piezocono.
I classici metodi lagrangiani agli elementi finiti, ampiamente utilizzati da decenni, non sono adatti alla simulazione di grandi deformazioni per i severi problemi conseguenti le estreme defromazioni della mesh.
La necessità di superare i limiti dei classici FEM, diversi gruppi di ricerca si sono impegnati, negli ultimi anni, a sviluppare nuovi metodi numerici tra cui si ricorda SPH, MPM e PFEM.
Nel Material Point Method il continuo deformabile è rappresentato da un insieme di punti materiali che si spostano attraverso una mesh fissa di elementi finiti.
I punti materiali trasportano tutte le informazioni del corpo come velocità, tensioni, deformazioni, proprietà del mateiale e carichi, mentre la mesh è utilizzata solo per risolvere le equazioni del moto, ma non memorizza alcuna informazione permamente; in questo modo si evitano problemi di distorsione degli elementi finiti.
L'interazione con l'acqua o altri fluidi interstiziali è determinante nel comportamento del terreno nella maggior parte delle condizioni di carico.
In condizione drenate e non drenate, la presenza dell'acqua può essere tratta in modo semplificato cos' che gli spostamenti del terreno possono essere calcolati con l'uso delle equazioni del continuomo monofase.
In molti casi è essenziale tener conto del movimento relativo tra lo scheletro solido e l'acqua, questo necessita dell'uso della formulazione bifase.
Entrambe queste possibiltà di simulare il terreno saturo vengono utilizzate nello studio dei problemi oggetto di questo studio.
Nel MPM problemi caratterizzati dal contatto fra corpi possono essere simulati con un algoritmo sviluppato specificatamente per l'MPM all'inizio del secolo; tale algoritmo viene ripreso in questa tesi ed esteso al caso dei terreni coesivi per la simulazione dell'interazione terrno-struttura.