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1
Brown, Steven Andrew. "Development of a coupled finite element - boundary element program for a microcomputer". Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45713.
Testo completoAbstract (sommario):
This thesis describes the development of a coupled finite element — boundary element program for a microcomputer. The steps outlined in the thesis include the adaptation of a mainframe—based boundary element code for use on a microcomputer, the Verification of this program with sample problems, the development of an algorithm for coupling the Finite Element Method to the Boundary Element Method, the implementation of the coupling
algorithm with finite element and boundary element codes, including the development of a Constant Strain Triangular finite element, and the Verification of the coupled program with sample problems. Conclusions are drawn from the results presented, and suggestions are made for future research in this area.Master of Science
2
McDavid, Charles Scott. "Weight optimum arch structures". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA245954.
Testo completoAbstract (sommario):
Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Salinas, David. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Arches, Stress Analysis, Weight, Finite Element Analysis, Computer Programs, Optimization, Theses, Degrees Of Freedom, FORTRAN, Stiffness, Case Studies. Author(s) subject terms: Finite Element Method, Arches, Weight Optimization. Includes bibliographical references (p. 107). Also available in print.
3
Wadham-Gagnon, Matthew. "Hyperelastic modelling of rubber behaviour in finite element software". Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99797.
Testo completoAbstract (sommario):
Experimental characterisation of rubber in uniaxial, equi-biaxial and planar tension under cyclic quasi-static loading shows strain-induced stress softening, hysteresis and unrecoverable strain. The objective of this work is to study the applications and limitations involved in predicting the behaviour of rubber with hyperelastic models. To assume a preconditioned perfectly elastic material, the data obtained from experiments must first be simplified. The data is then fitted to popular hyperelastic models in the finite element analysis (FEA) software ANSYS(TM). A single hyperelastic model (with given coefficients) is shown to only provide a good fit to a single characterisation test and level of preconditioning at the time. A two-iteration preconditioning method is developed using different hyperelastic models for a given material to approximate the softening effect of cyclic loading in a static FEA simulation. A biaxiality test is developed, providing information on the dominant mode of simple strain in the elements of a FE model. FEA simulations and experimental tests of a cantilevered rubber plate subjected to a bending load at its free end as well as a rubber guide lug subjected to a transverse deflection are presented and discussed. It is shown that using a single hyperelastic model is insufficient to predict the behaviour of these experiments in FEA simulations. The preconditioning iteration, when applied to these simulations, shows very good agreement with the experiments, both qualitatively and quantitatively. The biaxiality test provides insight on which characterisation test is the most appropriate for curve fitting hyperelastic models for a given analysis.
4
Ritter, Baird S. "Solution strategies for second order, nonlinear, one dimensional, two point boundary value problems by FEM analysis". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA246063.
Testo completoAbstract (sommario):
Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor: Salinas, D. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Boundary value problems, finite element analysis, differential equations, problem solving, theses, interpolation, iterations, one dimensional, computer programs, approximation/mathematics, linearity. Author(s) subject terms: Galerkin FEM, nonlinear, quasilinearization, linearization, interpolation, iteration, differential equation, convergence. Includes bibliographical references (p. 164). Also available in print.
5
Joglekar, Pramod N. "Three-dimensional finite element modeling of steady state seepage using the computer program 'SEEPS3D'". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06102009-063119/.
Testo completo
6
Ostendorp, Markus. "Improved Methodology for Limit States Finite Element Analysis of Lattice Type Structures using Nonlinear Post-Buckling Member Performance". PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/1179.
Testo completoAbstract (sommario):
In an attempt to achieve more efficient designs, the technological frontier is pushed further and further. Every year science probes for a better understanding of natural phenomena, discovering new and improved methods to perform the same task more efficiently and with better results. One of the new technologies is the nonlinear analysis of structural systems using inelastic post-buckling member performance. Inelastic post-buckling member performance is defined as the constitutive relationship between axial load and displacement after the ultimate member capacity has been exceeded. A nonlinear analysis is able to predict the failure behavior of a structural system under ultimate loads more accurately than the traditionally used linear elastic analysis. Consequently, designs can be improved and become more efficient, which reduces the realization cost of a project. An improved nonlinear analysis solution algorithm has been developed, that allows the analyst to perform a nonlinear analysis using post-buckling member performances faster than previously possible. Furthermore, the original post-buckling member performance database was expanded using results obtained from physical member compression tests. Based on the experimental results, new post-buckling member performance model curves were developed to be used together with the improved nonlinear solution algorithm. In addition, a program was developed that allows the analyst to perform a valid nonlinear analysis using a finite element program (LIMIT). The program combines a numerical pre-processor, and input and output data evaluation modules based on human expertise together with the LIMIT analysis package. Extensive on-line help facilities together with graphical pre- and post-processors were also integrated into the program. The resulting analysis package essentially combines all of the necessary components required to perform a nonlinear analysis using post-buckling member performances into one complete analysis package.
7
Pester, Matthias. "Visualization Tools for 2D and 3D Finite Element Programs - User's Manual". Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200600436.
Testo completoAbstract (sommario):
This paper deals with the visualization of
numerical results as a very convenient method to
understand and evaluate a solution which has been
calculated as a set of millions of numerical values.
One of the central research fields of the Chemnitz
SFB 393 is the analysis of parallel numerical
algorithms for large systems of linear equations
arising from differential equations (e.g. in solid
and fluid mechanics). Solving large problems on
massively parallel computers makes it more and
more impossible to store numerical data from the
distributed memory of the parallel computer to
the disk for later postprocessing. However, the
developer of algorithms is interested in an
on-line response of his algorithms. Both visual
and numerical response of the running program may
be evaluated by the user for a decision how to
switch or adjust interactively certain parameters
that may influence the solution process.
The paper gives a survey of current programmer
and user interfaces that are used in our various
2D and 3D parallel finite element programs for
the visualization of the solution.
8
Chan, Andrew Hin-Cheong. "A unified finite element solution to static and dynamic problems of geomechanics". Thesis, Swansea University, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624605.
Testo completo
9
Guney, Murat Efe. "High-performance direct solution of finite element problems on multi-core processors". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34662.
Testo completoAbstract (sommario):
A direct solution procedure is proposed and developed which exploits the parallelism that exists in current symmetric multiprocessing (SMP) multi-core processors. Several algorithms are proposed and developed to improve the performance of the direct solution of FE problems. A high-performance sparse direct solver is developed which allows experimentation with the newly developed and existing algorithms. The performance of the algorithms is investigated using a large set of FE problems. Furthermore, operation count estimations are developed to further assess various algorithms. An out-of-core version of the solver is developed to reduce the memory requirements for the solution. I/O is performed asynchronously without blocking the thread that makes the I/O request. Asynchronous I/O allows overlapping factorization and triangular solution computations with I/O. The performance of the developed solver is demonstrated on a large number of test problems. A problem with nearly 10 million degree of freedoms is solved on a low price desktop computer using the out-of-core version of the direct solver. Furthermore, the developed solver usually outperforms a commonly used shared memory solver.
10
Cook, William Digby. "Studies of reinforced concrete regions near discontinuities". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75457.
Testo completoAbstract (sommario):
A non-linear finite element computer program capable of predicting the complete response of two-dimensional reinforced concrete members was developed. This tool which accounts for the stress strain characteristics of cracked concrete was used to predict the responses of a number of members containing discontinuities. These members included corbels, dapped end beams, beams with web holes, and deep beams. The results of tests performed by the author as well as tests performed by other researchers were compared with the non-linear predictions. In addition, simple strut and tie models suitable for designing regions near discontinuities were developed. The predictions obtained by these models were compared with the non-linear finite element predictions and with the test results.
11
Sannes, Kevin Markle 1964. "Finite element analysis of aerosol particle deposition on surfaces inside a clean room". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277120.
Testo completoAbstract (sommario):
Aerosol particle deposition rates on surfaces inside a clean room are predicted by a model developed to account for particle convection, diffusion and sedimentation. External forces acting on the particle also influence the rate of deposition. Both electrical charge build up on product surfaces and temperature gradients in the air near the product surface are known to effect the rate of deposition. A description of an electrostatic and thermophoretic force on the particle is thus included in the model. The equations governing the particle deposition process and the approach used in obtaining a solution to these equations are both described. A finite element numerical solution is detailed, followed by a description of the electrostatic force models. Finally, predictions of the model are presented with a comparison to data experimentally obtained by other researchers.
12
Miltenberger, Louis C. "Finite element modeling of the filament winding process using ABAQUS". Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-06232009-063022/.
Testo completo
13
Stein, S. C. "Modelling of the filament-winding fabrication process". Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41585.
Testo completoAbstract (sommario):
A stress model of the filament-winding fabrication process, previously implemented in a finite element program, was improved. Pre- and post-processing codes were developed to make the program easier and more efficient to use. A program which is used to design filament wound composite rocket motor cases was modified to write a model file for the fabrication stress code in the pre-processing stage. The same code was altered to provide post-processing output in the form of graphic displays. Also, a new code was written to provide additional post-processing capability for the fabrication stress model.
Verification of the model of the filament-winding process was performed by comparing experimental pressure and strain data, for the fabrication of a filament wound bottle, with results of an analytical model. The final analytical results using consecutive models of the filament wound bottle show reasonable agreement with experimental pressure and hoop strain data. The maximum difference in the analytical and experimental values in the pressure data was about 25% for the final winding stage. The difference was smaller during the winding progression. These results also show that the accuracy of the model depends heavily on the assumptions made for input parameters during modelling. The stiffness of the segmented steel mandrel, simulated by an effective modulus (degraded by segmentation), and the instantaneous laydown tension loss parameters significantly affected the results of the model. Including the effective modulus for the segmented mandrel in the model reduced the difference in the experimental and analytical pressure results by about 150%. The inclusion of instantaneous laydown tension loss in the model reduced the analytical-experimental difference by roughly 225%. These two parameters reduced the largest difference in the predicted pressure values from about 400% for the first model to around 25% for the final model.
The fabrication stress model was coupled with the thermo-kinetic cure model to provide more accurate fiber motion tension loss analysis capability. The stress model was modified to use the thermo-kinetic model as a subroutine to calculate fiber motion tension loss using a two-dimensional analysis. The results of the qualitative verification show that fiber motion tension loss is more important in the later stages of winding than in the beginning stages which indicates that it may provide the needed accuracy in the final winding stages.Master of Science
14
Bahlis, Jihad. "An experimental-analytical investigation of hypoelastic models for plain and reinforced concrete /". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73996.
Testo completo
15
YORIYAZ, HELIO. "Implementacao de queima espacial modificando o programa nodal baseado no metodo de elementos finitos e matriz resposta". reponame:Repositório Institucional do IPEN, 1986. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9855.
Testo completoAbstract (sommario):
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
16
Sharpe, Alton Russell. "Functional validation of a novel technique for assembling high density polyimide cochlear implants". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45741.
Testo completoAbstract (sommario):
It has been hypothesized that increasing the number of active sites on a cochlear implant electrode array will enable the recipient to distinguish a higher number of pitch precepts, thus creating a more natural sound. While DSP processing strategies for cochlear implants have evolved significantly to address this, technology for the actual electrode array has remained relatively constant and limits the number of physical electrodes possible. Previous work introduced the concept of using Thin-Film Array (TFA) technology to allow for much higher site densities, although the original devices proved unreliable during surgical insertion tests. This work presents a new method of combining polyimide-based TFA's with supporting silicone insertion platforms to create assembled electrode arrays that are a more viable option for surgical insertion. The electrical and mechanical properties of these assemblies are investigated with physical deformation tests and finite element analysis in COMSOL to quantify how they will perform upon insertion into the cochlea, and the preliminary results of a surgical insertion study into human cadaveric temporal bones will be discussed.
17
Woods, Juliette Aimi. "Numerical accuracy of variable-density groundwater flow and solute transport simulations". Title page, contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phw8941.pdf.
Testo completo
18
Barrows, Richard James. "Two Dimensional Finite Element Modeling of Swift Delta Soil Nail Wall by "ABAQUS"". PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4741.
Testo completoAbstract (sommario):
Soil nail walls are a form of mechanical earth stabilization for cut situations. They consist of the introduction of passive inclusions (nails) into soil cut lifts. These nailed lifts are then tied together with a structural facing (usually shotcrete) . The wall lifts are constructed incrementally from the top of cut down. Soil nail walls are being recognized as having potential for large cost savings over other alternatives. The increasing need to provide high capacity roadways in restricted rights of way under structures such as bridges will require increasing use of techniques such as combined soil nail and piling walls. The Swift Delta Soil Nail wall required installing nails between some of the existing pipe piling on the Oregon Slough Bridge. This raised questions of whether the piling would undergo internal stress changes due to the nail wall construction. Thus, it was considered necessary to understand the soil nail wall structure interaction in relation to the existing pile supported abutment. The purpose of this study was to investigate the Swift Delta Wall using finite element (FE) modeling techniques. Valuable data were available from the instrumentation of the swift Delta Wall. These data were compared with the results of the FE modeling. This study attempts to answer the following two questions: 1. Is there potential for the introduction of new bending stresses to the existing piling? 2. Is the soil nail wall system influenced by the presence of the piling? A general purpose FE code called ABAQUS was used to perform both linear and non-linear analyses. The analyses showed that the piling definitely underwent some stress changes. In addition they also indicated that piling influence resulted in lower nail stresses. Comparison of measured data to predicted behavior showed good agreement in wall face deflection but inconsistent agreement in nail stresses. This demonstrated the difficulty of modeling a soil nail due to the many variables resulting from nail installation.
19
Forti, Nadia Cazarim da Silva. "Estudo parametrico de estruturas tubulares com ligações multiplanares". [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257812.
Testo completoAbstract (sommario):
Orientador: João Alberto Venegas RequenaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: Este trabalho apresenta um estudo paramétrico comparativo de ligações do tipo K e KK utilizando perfis tubulares circulares com afastamento entre diagonais e carregadas simetricamente. Para se comparar as ligações, foi desenvolvido um modelo numérico através do programa comercial de elementos finitos Ansys. Também foram desenvolvidos dois programas auxiliares para facilitar o estudo paramétrico. Foram analisadas 55 ligações do tipo KK e suas correspondentes K, comparando-se suas resistências. O objetivo deste trabalho é propor um critério objetivo para definir os modos de falha (1 e 2) da ligação tipo KK baseado na deformação diametral do banzo. O modo de falha 1 ocorre quando um par de diagonais vizinhas, carregadas no mesmo sentido, empurra ou puxa, a parede do banzo e no segundo, chamado modo 2 acontece uma deformação diametral da parede do banzo na região entre as diagonais vizinhas, criando quinas e dobras entre essas diagonais. Outro objetivo é estabelece uma demarcação do limite entre os dois modos de falha como uma função do afastamento transversal entre as diagonais. Os resultados permitiram o desenvolvimento de equações que preveem as resistências das ligações tipo KK, para os modos de falha 1 e 2 (plastificação da parede do banzo), a partir da resistência da ligação tipo K correspondente
Abstract: This work presents a parametric study of K and KK tubular steel connection. Gap connections with symmetric loading are analyzed. A numerical model using the commercial finite element software Ansys is proposed to compare K and KK connection resistances. Two auxiliary softwares are developed for setting the numerical model and to post-process results. A set of 55 KK connections and their correspondent K connections are analyzed and their resistances are compared. The objective of this work is purpose define the failure mode (1 or 2) of KK connections. This criteria is based on the chord diametric deformation. The results allowed the definition of limit values in function of the transversal gap for determining the connection failure mode. The connection resistance obtained in the parametric study allowed the development of an analytical expression which predict the KK connections resistance from the resistance of its correspondent K connection
Doutorado
Estruturas
Doutor em Engenharia Civil
20
Minchillo, Daniela Grintaci Vasconcellos. "Estudo de ligações pinadas com chapa de topo para aplicações em estruturas metálicas treliçadas tubulares planas". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257814.
Testo completoAbstract (sommario):
Orientador: João Alberto Venegas RequenaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: Este trabalho apresenta o desenvolvimento de uma concepção estrutural para ligações de treliças metálicas tubulares de seção circular com chapa de topo através de um estudo teórico-experimental. Nesta concepção as extremidades das diagonais são superpostas e unidas por um único parafuso fazendo com que a ligação seja pinada. A colocação da chapa faz com que apareça uma excentricidade na ligação originando esforços adicionais na estrutura que são aqui avaliados. Como vantagem desta ligação, destaca-se o baixo custo de fabricação, a rapidez de montagem das treliças, facilidade de transporte e versatilidade no detalhamento das ponteiras das diagonais. Pode ser utilizada em ligações de treliças planas ou multiplanares. Foi realizado um levantamento bibliográfico nas prescrições de cálculo e demais publicações, nacionais e internacionais, para ligações de estruturas tubulares, e um programa experimental foi desenvolvido com objetivo de certificar a ligação e obter um procedimento adequado para o cálculo da sua resistência. A análise experimental possibilitou a avaliação dos efeitos localizados na ligação, a interação entre a chapa e o perfil tubular e a identificação dos mecanismos de colapso. Os resultados experimentais são comparados com os resultados numéricos, que consideram como parâmetros, a influência do comprimento e da espessura da chapa de topo na resistência, no modo de colapso e na distribuição de tensões na ligação. Um modelo numérico, calibrado pelos resultados da análise experimental, foi utilizado para uma análise paramétrica. Com os resultados desta análise foi proposta uma formulação para obtenção da resistência da ligação
Abstract: This work presents a theoretical and experimental study of a gusset plate connection for application in trusses with circular hollow sections. In this connection the diagonals edges are superimposed and joined together at the plate by a single bolt causing the connection to be pinned. The placement of the plate leads to an eccentricity, resulting in additional efforts in the connection that are evaluated. Some of the advantages of this connection are the low manufacturing costs, the quickly assembly of trusses, versatility in the detailing of the braces ends and can be used properly on uniplanar or multiplanar trusses. A literature review is performed on codes, prescriptions and other publications, national and international for tubular connections, and an experimental program is developed in order to certify and obtain an appropriate procedure to determine the connection resistance. The experimental analysis allowed the evaluation of the local effects, the interaction between the gusset plate and tubular section and the identification of the failure modes. The experimental results are compared with numerical results considering parameters such as the influence of the length and thickness of the gusset plate in the connection resistance, failure mode and stress distribution. A numerical model, validated by the results of experimental analysis, was used for parametric analysis. With the parametric results, an analytical expression is proposed to predict the connection resistance
Doutorado
Estruturas
Doutor em Engenharia Civil
21
Coelho, da Silva Catherine Souto Costa 1986. "Estudo de ligações pinadas com chapa de topo para aplicações em estruturas metálicas treliçadas tubulares multiplanares". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258128.
Testo completoAbstract (sommario):
Orientador: João Alberto Venegas RequenaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: O objetivo deste trabalho é apresentar um tipo de ligação em treliças metálicas tubulares multiplanares de seção circular com chapa de topo. Nestas ligações as extremidades das diagonais são superpostas e unidas por um único parafuso fazendo com que a ligação seja pinada. A colocação da chapa de topo implica no aparecimento de uma excentricidade na ligação originando esforços adicionais na estrutura. Esse tipo de ligação tem como vantagem o baixo custo de fabricação, a rapidez de montagem das treliças, a facilidade de transporte e a versatilidade no detalhamento das ponteiras das diagonais. Foi realizado um levantamento bibliográfico nas prescrições de cálculo e demais publicações, nacionais e internacionais, para ligações de estruturas tubulares e encontrou-se um estudo para esse tipo de ligação, mas apenas analisando treliças planas. Para verificar o comportamento da ligação, serão analisados modelos numéricos desenvolvidos com o programa de elementos finitos ANSYS 14.0. Os resultados encontrados com esses modelos serão analisados e comparados com os resultados numéricos encontrados na pesquisa de ligação pinada com chapa em treliças tubulares planares para elaboração de um fator de correção entre os dois tipos de ligação
Abstract: This paper objective is to propose a connection type for tubular steel trusses with circular section, multiplanar and with gusset plate. In these connections the ends of the diagonals are overlapped and joined by a single pin resulting a pinned connection. The position of the gusset plate in the connections implies an eccentricity which results in additional efforts in the structure. The advantage of this connection type is the low manufacturing cost, the fast erection of trusses, the easier transportation and the versatility in the detailing constructive of the diagonals end. Survey in technical books, standards, manuals and scientific articles was made for tubular steel structures connection. In this survey was found a research for a similar type of connection, but in this there were only analysis of planar trusses. Numerical models using the commercial finite element software ANSYS 14.0 will be analyzed to check the connection. The results from these models will be analyzed and compared with numerical results in the bibliographic review about planar truss for preparation of a correction factor between the two types of connection. OBSERVAÇÃOA palavra gusset nas palavras chaves, título em inglês e no abstract devem ser grifadas em itálico
Mestrado
Estruturas e Geotécnica
Mestra em Engenharia Civil
22
Raby, Douglas Allan. "Development of a system architecture and applications for an integrated computer software system for the analysis and design of steel structures". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0017/MQ48372.pdf.
Testo completo
23
Dressler, Bernhard. "Modélisation numérique des coques en grandes transformations : mise en oeuvre dans un environnement orienté objet". Châtenay-Malabry, Ecole centrale de Paris, 1997. http://www.theses.fr/1997ECAP0522.
Testo completoAbstract (sommario):
Ce mémoire est consacré à la dynamique des coques en grandes rotations. La théorie bidimensionnelle des coques est déduite du principe des travaux virtuels d'un milieu continu tridimensionnel en introduisant la cinématique de Mindlin. On obtient un système d'équations non-linéaires qui est linéarise par rapport aux déplacements de la surface moyenne ainsi que par rapport aux paramètres de rotation. La paramétrisation des grandes rotations par le vecteur de rotation est comparée à la paramétrisation directe par la matrice de rotation. En vue d'une discrétisation en éléments finis isoparamétriques on utilise des objets tensoriels intrinsèques qui sont ramenés a une configuration de référence aplatie. Cette configuration aplatie est identifiée à l'élément de référence. En dehors d'une loi de comportement hyper élastique on présente deux lois élastoplastiques en grandes transformations supposant que les déformations locales restent petites. Les efforts résultants sont obtenus ou par une intégration numérique dans l'épaisseur ou a partir d'une loi de comportement globale qui est directement formulée en efforts résultants. L’implémentation numérique est effectuée dans un environnement de programmation orientée objet qui a été développe pour l'analyse non-linéaire par la méthode des éléments finis. En particulier, on regarde le rôle des grandes rotations dans le calcul de la matrice de rigidité tangente. Des résultats numériques confirment l'efficacité de cette approche.
24
Pack, Peter Michael Walter. "The finite element method in underwater acoustics". Thesis, University of Southampton, 1986. https://eprints.soton.ac.uk/52298/.
Testo completoAbstract (sommario):
A Finite Element Method (FEM) is developed to calculate rotationally symmetric acoustic propagation over short range intervals (0-5 km) in shallow oceans (0-200 m deep) at low frequencies (0-50 Hz). The method allows full two-way wave propagation in range dependent environments and includes coupling to a full elastic seabed. Numerical results from a computer program are presented for propagation upslope, downslope, over seamounts and across trenches in the seabed. The seabed is modelled as a pressure release surface, a fluid halfspace and an elastic, solid halfspace and the implications of each type of model are discussed. The halfspaces, being represented by a new set of infinite elements, are modelled without truncation. The results are presented primarily as plots of transmission loss against range for a fixed depth receiver. Subsidiary results show the effect of depth averaging the receiver location, and extract mode amplitude data to reveal the strength of mode coupling and backscatter in different environments.
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Salles, Bruno Barbosa de Oliveira Ferreira. "Otimização da superfície de deslizamento em mancais hidrodinâmicos radiais com carregamento estático". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263511.
Testo completoAbstract (sommario):
Orientador: Marco Lúcio BittencourtDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho tem por objetivo desenvolver um algoritmo computacional para otimização de forma da superfície de mancais hidrodinâmicos. O algoritmo usa a teoria de lubrificação elastohidrodinâmica que leva em conta a deformação elástica do mancal devido à distribuição de pressão hidrodinâmica. Esta distribuição de pressão é calculada resolvendo-se a equação de Reynolds por meio do Método de Elementos Finitos (MEF). O MEF também foi usado para calcular a deformação radial do mancal. Uma metodologia de otimização foi então aplicada para obter um novo mancal com melhor desempenho, mudando-se apenas a geometria da superfície do mancal
Abstract: The aim of this work is to develop a computational algorithm for bearing surface shape optimization. The algorithm uses the elastohydrodynamic lubrication theory that takes into account the elastic bearing deformation due to the hydrodynamic pressure distribution. This pressure distribution is calculated by solving the Reynolds equation using the Finite Element Method (FEM). The FEM is also used to calculate the bearing radial deformation. An optimization methodology is applied to obtain a new bearing with better performance characteristics by changing only the geometry of the bearing surface
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Villard, Pascal. "Etude du renforcement des sables par des fils continus : modelisation et applications". Nantes, 1988. http://www.theses.fr/1988NANT2017.
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Modele numerique du materiau texsol, en associant un modele elastoplastique pour le sol (vermeer) et une loi non lineaire integrant les caracteristiques des fils (dosage, orientation, distribution). Developpement de deux logiciels par elements finis: problemes axisymetriques (comparaison a essais triaxiaux) et en deformation plane (murs)
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Zheng, Yi. "Finite Element Analysis for Fixture Stiffness". Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-050505-130954/.
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Barbier, Christine. "Computer algebra and transputers applied to the finite element method". Thesis, Durham University, 1992. http://etheses.dur.ac.uk/6112/.
Testo completoAbstract (sommario):
Recent developments in computing technology have opened new prospects for computationally intensive numerical methods such as the finite element method. More complex and refined problems can be solved, for example increased number and order of the elements improving accuracy. The power of Computer Algebra systems and parallel processing techniques is expected to bring significant improvement in such methods. The main objective of this work has been to assess the use of these techniques in the finite element method. The generation of interpolation functions and element matrices has been investigated using Computer Algebra. Symbolic expressions were obtained automatically and efficiently converted into FORTRAN routines. Shape functions based on Lagrange polynomials and mapping functions for infinite elements were considered. One and two dimensional element matrices for bending problems based on Hermite polynomials were also derived. Parallel solvers for systems of linear equations have been developed since such systems often arise in numerical methods. Both symmetric and asymmetric solvers have been considered. The implementation was on Transputer-based machines. The speed-ups obtained are good. An analysis by finite element method of a free surface flow over a spillway has been carried out. Computer Algebra was used to derive the integrand of the element matrices and their numerical evaluation was done in parallel on a Transputer-based machine. A graphical interface was developed to enable the visualisation of the free surface and the influence of the parameters. The speed- ups obtained were good. Convergence of the iterative solution method used was good for gated spillways. Some problems experienced with the non-gated spillways have lead to a discussion and tests of the potential factors of instability.
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Kanellopoulos, Vassilios N. "Vectorial finite element analysis of E-plane waveguide junctions". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64027.
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Cenanovic, Mirza. "Finite element methods for surface problems". Doctoral thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Produktutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-35369.
Testo completoAbstract (sommario):
The purpose of this thesis is to further develop numerical methods for solving surface problems by utilizing tangential calculus and the trace finite element method. Direct computation on the surface is possible by the use of tangential calculus, in contrast to the classical approach of mapping 2D parametric surfaces to 3D surfaces by means of differential geometry operators. Using tangential calculus, the problem formulation is only dependent on the position and normal vectors of the 3D surface. Tangential calculus thus enables a clean, simple and inexpensive formulation and implementation of finite element methods for surface problems. Meshing techniques are greatly simplified from the end-user perspective by utilizing an unfitted finite element method called the Trace Finite Element Method, in which the basic idea is to embed the surface in a higher dimensional mesh and use the shape functions of this background mesh for the discretization of the partial differential equation. This method makes it possible to model surfaces implicitly and solve surface problems without the need for expensive meshing/re-meshing techniques especially for moving surfaces or surfaces embedded in 3D solids, so called embedded interface problems. Using these two approaches, numerical methods for solving three surface problems are proposed: 1) minimal surface problems, in which the form that minimizes the mean curvature was computed by iterative update of a level-set function discretized using TraceFEM and driven by advection, for which the velocity field was given by the mean curvature flow, 2) elastic membrane problems discretized using linear and higher order TraceFEM, which makes it straightforward to embed complex geometries of membrane models into an elastic bulk for reinforcement and 3) stabilized, accurate vertex normal and mean curvature estimation with local refinement on triangulated surfaces. In this thesis the basics of the two main approaches are presented, some aspects such as stabilization and surface reconstruction are further developed, evaluated and numerically analyzed, details on implementations are provided and the current state of work is presented.
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Pluma, Reyes Jorge A. "Fracture Control Modeling With The Finite Element Method". DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2096.
Testo completoAbstract (sommario):
This thesis investigates the feasibility and usability of the finite element method approach in the design of crack arresting devices. Current design and manufacturing practices are improving structures' susceptibility to fracture, in particular brittle fracture; however, cracks in structures are still observed within their lifespans due to severe unexpected service conditions, poor designs, or faulty manufacturing. Crack arrester systems can be added during service to prolong the longevity of structures with sub-critical or critical flaws. Fracture properties of different specific structures under specific services can be obtained experimentally, however, experiments are expensive and of high complexity. Alternatively, the finite element method can reduce these factors and provide reliable solutions. Finite element analysis conducted provides insight into the modeling process and the effectiveness of the simulation of fracture problems. Fracture mechanics technology in conjunction with the finite element method allows for the evaluation of the effectiveness of introducing crack arresters to a flawed structure. Additionally, the simulation of recorded crack arrester experiments alongside analytic methods are used to verify the finite element analysis results. The work in this thesis verifies the validity of using the finite element approach in designing crack arrester systems for flawed structures and suggests further investigation be done with variation in crack arrester types.
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Zhao, Yufei. "Computer modelling of cloth objects /". Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18614061.
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Froncioni, Andy M. "A new finite element method for analysis of H-plane waveguide junctions /". Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63937.
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Pinchuk, Amy Ruth. "Spectrally correct finite element analysis of electromagnetic fields". Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75780.
Testo completoAbstract (sommario):
Direct solution for three dimensional electric or magnetic field vectors throughout the frequency spectrum is accomplished by a finite element formulation which includes displacement and conduction currents, and requires no special treatment for material interfaces. Analysis of bus bar and Bath cube eddy current problems demonstrate the capabilities of the method.Spurious components in solutions to vector field problems are shown to corrupt deterministic solutions. These corruptions are identifiable with spurious modes familiar to high frequency modal analysis. Spectrally correct mixed order finite elements are demonstrated to retrieve accuracy in deterministic analyses.
The formulation may be limited by computer round-off at matrix assembly which affects the solenoidality of vector fields. Furthermore, extreme values encountered in low frequency eddy current analysis lead to ill conditioning and unreliable solutions. These numerical instabilities are overcome by parametric adjustment of permittivities. Error estimates are established to monitor inaccuracies introduced by permittivity adjustment.
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INOUE, NELSON. "IMPLEMENTATION OF A COMPUTER CODE CONSIDERING THE COUPLING OF THE FINITE ELEMENT METHOD (FEM) AND THE BOUNDARY ELEMENT METHOD (BEM)". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1522@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOO presente trabalho tem como principais objetivos estudar a formulação do método dos elementos de contorno e implementar um programa computacional para análise de tensões de problemas bi-dimensionais (estado plano de deformação e axissimetria) considerando também a possibilidade de acoplamento dos métodos dos elementos de contorno (MEC) e dos elementos finitos (MEF). Dentro deste estudo são abordados as soluções fundamentais para materiais linearmente elásticos, a formulação das integrais no contorno, as técnicas para tratamento de singularidade, a utilização de nós duplos para estudos de canto, etc. Os resultados numéricos obtidos em alguns problemas bi-dimensionais pelos métodos dos elementos de contorno e dos elementos finitos, considerando isoladamente ou acoplados, são comparados mutuamente e com soluções analíticas da teoria da elasticidade linear. Vantagens e desvantagens destes métodos, bem como dificuldades de implementação numérica, são discutidas ao longo deste trabalho.
The main objectives of this work are the study of the boundary element formulation as well as the implementation of computer program for stress analyses of bidimensional problems under axisymmetric or plane strain conditions. The computer program also combines the boundary element method (BEM) with the finite element method (FEM) thus permitting its application to wide range of geotechnical problems. In this study research several mathematical aspects of the boundary element method are reviewed, such as the fundamental solutions for elastic materials, contour integration, singularities, corner problems, etc. The numeric results obtained in some 2D problems the BEM and FEM, in a coupled or isolated form, are compared with analytical solutions provided by classical theory of elasticity. Advantages and shortcomings of both methods, as well as the difficulties in the computer implementation, are also discussed in this work.
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Loubenets, Alexei. "An Immersed Finite Element Method and its Application to Multiphase Problems". Doctoral thesis, Stockholm : Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4514.
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Villeneuve, Donald. "A p-type finite element method for devices with nonlinear materials and curved boundaries". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0025/NQ50324.pdf.
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趙宇飛 e Yufei Zhao. "Computer modelling of cloth objects". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31236431.
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Naqib, Rami Abdul-Ghani. "Shape optimization of two-dimensional eleastic continuum using finite element analysis". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/32790.
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Ren, Zhen. "Modular model assembly from finite element models of components". Diss., Connect to online resource - MSU authorized users, 2008.
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Owen, David R. "Random search of AND-OR graphs representing finite-state models". Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2317.
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Thesis (M.S.)--West Virginia University, 2002.Title from document title page. Document formatted into pages; contains vi, 96 p. : ill. Includes abstract. Includes bibliographical references (p. 91-96).
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Sharp, Richard Paul. "Computational approaches for diffusive light transport finite-elements, grid adaption, and error estimation /". Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1154705561.
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Chen, Guodong. "Solution of diffusion equation in axisymmetrical coordinates". Ohio : Ohio University, 1994. http://www.ohiolink.edu/etd/view.cgi?ohiou1176840295.
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Pvillalta, Jose Samuel. "FINITE ELEMENT-BOUNDARY INTEGRAL METHOD AND ITS APPLICATION TO IMPLANTABLE ANTENNA DESIGN FOR WIRELESS DATA TELEMETRY". MSSTATE, 2006. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07072006-114241/.
Testo completoAbstract (sommario):
A non-stationary Krylov subspace based iterative solver for the three dimensional finite element-boundary integral (FE-BI) method for implantable antennas is presented. The present method numerically solves the frequency domain Maxwell?s equations in the variational form to formulate the finite element solution using hexahedral discretization elements in conjunction with the appropriate boundary integral equations. Four different solvers are used to investigate the convergence behavior of the FE-BI technique on the design of the antennas. The scheme is then applied to two miniaturized planar inverted-F antennas (PIFA): a serpentine and a spiral. The antennas are designed for the Medical Implant Communication Service (MICS) band (402-405 MHz). Validations and comparisons are done using High Frequency Electromagnetic Simulation (HFSS) software. Return loss, gain, near fields, and far fields are presented for the serpentine and spiral antenna.
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Marais, Neilen. "Higher order hierarchal curvilinear triangular vector elements for the finite element method in computational electromagnetics". Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53447.
Testo completoAbstract (sommario):
Thesis (MScEng)--Stellenbosch University, 2003.ENGLISH ABSTRACT: The Finite Element Method (FEM) as applied to Computational Electromagnetics (CEM), can be used to solve a large class of Electromagnetics problems with high accuracy, and good computational efficiency. Computational efficiency can be improved by using element basis functions of higher order. If, however, the chosen element type is not able to accurately discretise the computational domain, the converse might be true. This paper investigates the application of elements with curved sides, and higher order basis functions, to computational domains with curved boundaries. It is shown that these elements greatly improve the computational efficiency of the FEM applied to such domains, as compared to using elements with straight sides, and/or low order bases.
AFRIKAANSE OPSOMMING: Die Eindige Element Metode (EEM) kan breedvoerig op Numeriese Elektromagnetika toegepas word, met uitstekende akkuraatheid en 'n hoë doeltreffendheids vlak. Numeriese doeltreffendheid kan verbeter word deur van hoër orde element basisfunksies gebruik te maak. Indien die element egter nie die numeriese domein effektief kan diskretiseer nie, mag die omgekeerde geld. Hierdie tesis ondersoek die toepassing van elemente met geboë sye, en hoër orde basisfunksies, op numeriese domeine met geboë grense. Daar word getoon dat sulke elemente 'n noemenswaardinge verbetering in die numeriese doeltreffendheid van die EEM meebring, vergeleke met reguit- en/of laer-orde elemente.
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Burge, David Henry. "Experimental validation of roll force and profile fill for a profile ring rolling computer model". Ohio : Ohio University, 1996. http://www.ohiolink.edu/etd/view.cgi?ohiou1178657382.
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Tongtoe, Samruam. "A comparison of displacement and hybrid stress models for two dimensional finite element analysis". Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/80094.
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An eight-node isoparametric hybrid stress element is developed for two dimensional plane stress and plane strain analyses. The assumed stresses are represented by 18 unknown parameters. An eight-node isoparametric displacement element is implemented in an existing finite element program [10]. Several example problems are solved to compare the results of the hybrid and the displacement elements.Master of Science
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Chen, David Tzu-Wei. "Pump it up : computer animation of a biomechanically based model of muscle using the finite element method". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13139.
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Charras, Guillaume Thomas. "Digital Image-Based Finite Element Modeling (DIBFEM) : validation and application to biological structures". Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17765.
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Mudrich, Jaime. "Development of a Coupling Model for Fluid-Structure Interaction using the Mesh-free Finite Element Method and the Lattice Boltzmann Method". FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/964.
Testo completoAbstract (sommario):
In the presented thesis work, the meshfree method with distance fields was coupled with the lattice Boltzmann method to obtain solutions of fluid-structure interaction problems. The thesis work involved development and implementation of numerical algorithms, data structure, and software. Numerical and computational properties of the coupling algorithm combining the meshfree method with distance fields and the lattice Boltzmann method were investigated. Convergence and accuracy of the methodology was validated by analytical solutions.
The research was focused on fluid-structure interaction solutions in complex, mesh-resistant domains as both the lattice Boltzmann method and the meshfree method with distance fields are particularly adept in these situations. Furthermore, the fluid solution provided by the lattice Boltzmann method is massively scalable, allowing extensive use of cutting edge parallel computing resources to accelerate this phase of the solution process. The meshfree method with distance fields allows for exact satisfaction of boundary conditions making it possible to exactly capture the effects of the fluid field on the solid structure.