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1
Quan, Liang. „Using FDM and FEM to simulate the decarburization in AISI 1074 during heat processing and its impact“. Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44769.
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The metallurgical processes and the products developed from these processes have been the cornerstone on which our civilizations have developed and flourished. Many of the new materials that have been developed over centuries were often the result of serendipitous occurrences. Because of the importance of new materials to the improvement of society, it is necessary to accelerate the way in which new alloys and processes are designed, developed and implemented.
Over the last two decades the computational side of materials science has thrived as a result of bigger and faster computers. However, the application of new computational methods to the development of new materials and structures is still in the early stages primarily because of the complexity of most metallurgical processes. One such process is the decarburization of steel. Because of the importance of the microstructure on the mechanical properties, changes in the near surface properties are affected by the loss of carbon in the alloy. The topics investigated in this thesis include a variety of alloys and microstructures that are considered to be important in the development of a unique structure necessary for a more efficient method of recovering natural gas and oil from underground reserves as well as structures for energy absorbing systems. Since both the material application and the structure are new, this research represents an ideal opportunity to combine processing, properties, microstructure and computations to accelerate the development of these new structures.
Compared to other commercially available proppants which tend to fail in demanding environments, the thin-walled hollow metal proppants are regarded more promising due to the low density and high mechanical strength. The energy-absorbing composite material manufactured by embedding said spheres in the Mg/Al matrix material is optimized by improving sphere and matrix properties at each step in the process. Ultimately the mechanical strength, fracture toughness, and energy absorption are expected to achieve a factor of 2-5 higher than previously reported.
Modeling makes it economically practical to assess the targeted materials' overall properties, behaviors and the mechanical responses in conjunction with stress environment, material properties, material dimensions among other variables, before a structure is built. Additionally, more advanced modeling can enable the quantitative descriptions of more complex metallurgical phenomena such as the effects of impurity elements and deformation under complex loading conditions.
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Sayar, Sepideh. „Heat Transfer During Melting and Solidification in Heterogeneous Materials“. Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/36147.
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A one-dimensional model of a heterogeneous material consisting of a matrix with embedded separated particles is considered, and the melting or solidification of the particles is investigated. The matrix is in imperfect contact with the particles, and the lumped capacity approximation applies to each individual particle. Heat is generated inside the particles or is transferred from the matrix to the particles coupled through a contact conductance. The matrix is not allowed to change phase and energy is either generated inside the matrix or transferred from the boundaries, which is initially conducted through the matrix material. The physical model of this coupled, two-step heat transfer process is solved using the energy method.
The investigation is conducted in several phases using a building block approach. First, a lumped capacity system during phase transition is studied, then a one-dimensional homogeneous material during phase change is investigated, and finally the one-dimensional heterogeneous material is analyzed. A numerical solution based on the finite difference method is used to solve the model equations. This method allows for any kind of boundary conditions, any combination of material properties, particle sizes and contact conductance. In addition, computer programs, using Mathematica, are developed for the lumped capacity system, homogeneous material, and heterogeneous material. Results show the effects of control volume thickness, time step, contact conductance, material properties, internal sources, and external sources.Master of Science
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NOVOA, DANNY MESIAS CHAVEZ. „PHYSICAL -CHEMICAL EVALUATION OF HIGH DENSITY POLYETHYLENE PROCESSED BY THE 3D PRINTING METHOD OF FUSED DEPOSITION MODELING FDM“. PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24466@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
O objetivo deste trabalho foi estudar a influencia das condições da impressão 3D nas propriedades finais do polietileno de alta densidade usando a modelagem por fusão e deposição, FDM. Foram impressos protótipos com formato de corpos de prova para teste de tração tipo V segundo norma ASTM D638, a três temperaturas de processamento: 220, 240 e 260 Graus Celsius. Para a impressão das amostras foram mantidos constantes os parâmetros de controle, entre eles a espessura da camada de impressão. As amostras impressas foram caracterizadas por difração de raios X, espectroscopia infravermelha, calorimetria diferencial de varredura, análise termogravimétrica, ensaio de tração, índice de fluidez e teste de contração. Os resultados das caracterizações das amostras impressas foram comparados com os resultados do material sem processar, cujas propriedades foram obtidas usando os mesmo métodos de caracterização. Estes resultados demostraram que as condições de impressão por FDM empregadas neste trabalho causaram apenas uma leve mudança nas características estruturais das amostras processadas do PEAD em relação ao material original sem processamento. Houve um leve aumento da cristalinidade no PEAD impresso (em torno de 1,3 a 3 porcento). Além disso, foi comprovado que por causa do resfriamento desigual na superfície e no interior da amostra impressa, o grau de cristalinidade foi levemente maior no interior que na superfície do corpo de prova impresso. A leve mudança no grau de cristalinidade não foi suficiente para causar mudança no módulo de elasticidade e no limite de escoamento em relação ao PEAD original. Outros resultados demostraram que não houve mudança significativa envolvendo formação de ligações duplas, quebra de cadeias e degradação térmica por efeito da condição do processamento utilizada durante a impressão.
The aim of this work was to study the influence of process conditions for 3D printing on the final properties of prototypes of high density polyethylene (HDPE) using the method of the fused deposition modeling. Prototypes for type-V tensile testing according to ASTM D 638 were printed; They were made to three processing temperatures: 220, 240 and 260 Celsius degree. Control parameters for printing were kept constant in all the samples. The printed samples were characterized by X – ray diffraction, infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, tensile test, melt flow index test, and, shrinkage test. The results of the characterization of the printed samples and of the original material were compared. These results demonstrated that the printing conditions employed in this study caused a slight change in the structural characteristics of the printed samples compared to the unprocessed original material, there being a slight increase in crystallinity (about 1,3 to 3 percent) for HDPE which was printed. In addition, it has been proven that the degree of crystallinity was slightly greater on the inside that on the surface of the printed samples, because of uneven cooling on the surface and inside of these samples. The slight change in the degree of crystallinity was not enough to cause change in the elastic modulus and yield strength compared to the original HDPE. Other results showed that there was not significant change involving bond formation, break chains, and, thermal degradation by the effect of the processing conditions used during printing.
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Almeida, Wagner José de. „Otimização estrutural de protótipos fabricados pela tecnologia FDM utilizando o método dos elementos finitos“. Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18146/tde-05022010-163333/.
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Este trabalho tem como objetivo principal a otimização dos protótipos fabricados pelo processo FDM (Fused Deposition Modeling) em procedimento baseado na análise do comportamento estrutural dos protótipos variando as estratégias de preenchimento das camadas. Para atingir tal objetivo, corpos de prova com diferentes orientações de preenchimento foram ensaiados experimentalmente e os resultados foram verificados em análise estrutural por elementos finitos. Foram verificados o caráter ortotrópico do material do protótipo e a validade do uso da Teoria Clássica dos Laminados na simulação de seu comportamento. Os conceitos e metodologia de análise foram validados em estudos de casos, mostrando a viabilidade de sua aplicação na obtenção de protótipos funcionaisThe objective of this work is to develop an optimization procedure for FDM prototypes. This procedure is based on the structural analysis of the prototypes within different slice filling paths. In order to reach this objective, experimental tests with different filling trajectories are conducted and the results are used in structural analysis by finite element method. The orthotropic behavior of the prototype material and the use of the Classical Laminate Theory in the numerical simulation were validated. The results were applied in different case studies, showing the viability of its application in the design of functional prototypes.
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Moraes, Tiago Bueno de. „O método da diagonalização filtrada (FDM) e suas aplicações para a Ressonância Magnética“. Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-16092011-084245/.
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Este trabalho consiste em realizar um estudo detalhado das vantagens e desvantagens da utilização do FDM (Filter Diagonalization Method) para a análise de dados obtidos pela sequência de Precessão Livre no Estado Estacionário (Steady State Free Precession - SSFP) para aquisição rápida de espectros de Ressonância Magnética Nuclear (RMN). No caso de RMN de baixa resolução, o procedimento de aquisição rápida, SSFP, é uma poderosa ferramenta para melhorar a relação sinal/ruído, apresentando muitas aplicações práticas. Apesar desse sucesso em baixa resolução, a SSFP não é rotineiramente utilizada para aplicações em RMN de alta resolução, provavelmente devido ao (1) artefatos provenientes do truncamento do sinal e (2) as anomalias causadas pela mistura do FID com o eco dos sinais. Existem na literatura inúmeras possíveis técnicas para suprimir este tipo de problemas, porém, nenhuma delas é capaz de realmente eliminar as anomalias geradas devido ao procedimento de aquisição rápida da SSFP. O FDM é um método paramétrico não-linear para fitar sinais no domínio do tempo. Seu objetivo fundamental é resolver o Problema da Inversão Harmônica, HIP, tornando-se robusto e adequado para a análise espectral de sinais no domínio do tempo nos casos onde a Transformada de Fourier falha. Neste trabalho, demonstramos que o FDM pode ser implementado para análises de sinais SSFP, com mais eficiência que os obtidos pelos procedimentos padrões de TF. A temperatura ambiente, espectros de RMN 13C de amostras de brucina, obtidos com tempo entre pulsos de 100ms, podem ser reproduzidos com boa relação sinal/ruído e alta resolução por meio do FDM. A limitação da análise por FDM é mais relevante nos casos de espectros com alta densidade de picos em uma determinada região espectral. Nestes casos, o curto período de observação do sinal na janela do tempo impõe uma série de limitações na resolução obtida pelo FDM.This work consists in a detailed study of the advantages and disadvantages of the use of the Filter Diagonalization Method, FDM, for data analysis in Steady State Free Precession, SSFP, technique, usually employed to implement fast acquisition of Nuclear Magnetic Resonance, NMR, spectra. In the case of low resolution NMR using fast acquisition procedures, SSFP is a powerful tool to improve signal-to-noise ratio, presenting several important practical applications. Despite its success in the low resolution regime, SSFP is not a routine technique for high resolution applications, so far, mainly because of (1) truncation artifacts and (2) the intrinsic anomalies caused by admixture of free-induction-decay and echo signals. The literature reports many possible techniques to solve such kind of problems, but, none of them is capable to really eliminate the generated spectra anomalies caused by the fast acquisition procedure used in SSFP. FDM is a parametric method for non-liner fitting performed in the time domain. Its main goal is to solve the Harmonic Inversion Problem, HIP, making it robust and suitable for spectral analysis of time signals in the cases where the Fourier Transform, FT, technique fail. In this work we demonstrate that FDM can be used to implement the analysis of the SSFP data, with more efficiency than that achieve by appropriated FT procedures. Room temperature 13C NMR spectra of brucine samples, obtained from pulse sequences with 100 ms repetition time, can be reproduced with good signal-to-noise ratio and high resolution by means of the FDM. The limitation of the FDM analysis is more relevant in the case of spectra with a high density of peaks in a limited spectral frequency region. In these cases, the reduced short observation time window imposes serious limitation to the resolution achieved by the FDM.
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Strnad, Jiří. „Návrh malé multifunkční modelářské CNC frézky“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-444277.
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This diploma thesis deals with the construction proposal of a small multifunctional modeller CNC milling machine that enables milling of aluminium alloys and 3D printing using the FDM method. Based on the research, analyzes and defined entry requirements the construction proposal is created and verified by calculations. The thesis contains a description of all the construction parts including the printhead, the tool tray and the safety cover. The other part of the thesis describes the machine geometry adjustment and specifies the choice of control system. The thesis includes a 3D model and the drawing documentation of selected structural nodes.
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Kleditzsch, Stefan, und Birgit Awiszus. „Modeling of Cylindrical Flow Forming Processes with Numerical and Elementary Methods“. Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-97124.
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With flow forming – an incremental forming process – the final geometry of a component is achieved by a multitude of minor sequential forming steps. Due to this incremental characteristic associated with the variable application of the tools and kinematic shape forming, it is mainly suitable for small and medium quantities. For the extensive use of the process it is necessary to have appropriate simulation tools. While the Finite-Element-Analysis (FEA) is an acknowledged simulation tool for the modeling and optimization of forming technology, the use of FEA for the incremental forming processes is associated with very long computation times. For this reason a simulation method called FloSim, based on the upper bound method, was developed for cylindrical flow forming processes at the Chair of Virtual Production Engineering, which allows the simulation of the process within a few minutes. This method was improved by the work presented with the possibility of geometry computation during the process.
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Silva, Cíntia Maira Pereira da. „KBDM como ferramenta para processamento de sinais de Espectroscopia por Ressonância Magnética“. Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-12022014-075510/.
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A precisão e acurácia dos métodos mais utilizados atualmente de processamento de dados de espectroscopia por Ressonância Magnética (MRS), baseados na Transformada de Fourier (FT), requerem supressão apropriada (o que está longe de ser trivial) e aquisições longas para a obtenção de alta resolução espectral. Além disso, a FT tem dificuldades quando faltam dados no domínio de tempo, como, por exemplo, pela redução do tempo de aquisição, e consequente número de pontos adquiridos. Isto pode ocorrer, também, por artefatos na aquisição ou, ainda, seja pela exclusão intencional dos primeiros pontos do sinal para a eliminação de ressonâncias largas que estão distorcendo a linha de base no domínio da frequência. Neste estudo, propomos a utilização do Método de Diagonalização na Base de Krylov (KBDM) como uma alternativa a FT para algumas de suas limitações. O método ajusta sinais de experimentos de Free Induction Decay (FID) por uma soma de funções harmônicas complexas, amortecidas exponencialmente, permitindo uma fácil manipulação dos seus parâmetros de caracterização. O KBDM é numericamente mais efetivo para análise de sinais truncados e tem diversos recursos que possibilitam remover picos de forma mais eficiente, como por exemplo, o pico residual da água. Além disso, foi introduzida a possibilidade de quantificação de dados de MRS com o método. Para avaliar a sensibilidade, eficiência e reprodutibilidade do método para quantificar e analisar sinais truncados, foi proposto fazer simulações de espectros clínicos e experimentos em phantoms que representassem o ambiente metabólico do cérebro, para MRS de próton de diferentes níveis de ruídos e para pequenas variações do N-acetil aspartato (NAA). Com estes estudos pôde se comprovar a viabilidade do método para processar dados de MRS e verificar seu potencial na complementação das técnicas atualmente empregadas, especialmente quando uma resolução espectral e temporal maior que o limite imposto pela Relação de Incerteza do formalismo de Fourier é necessária. Além disso, uma desejável facilidade de manipulação de picos específicos (por exemplo, exclusão e quantificação) é proporcionada pelo método. Como perspectivas animadoras deste trabalho esperamos a introdução do KBDM como uma técnica eficiente e coadjuvante ao Imageamento de Ressonância Magnética funcional (fMRI), auxiliando estudos de funções cerebrais, em sequências de MRS para identificar uma rápida variação das linhas associadas as atividades metabólicas dos cérebros.The precision and accuracy of the most widely used methods to perform Magnetic Resonance Spectroscopy (MRS) data processing based on the Fourier Transform (FT), require appropriate suppression (which is far from trivial) and long acquisitions to obtain high spectral resolution. Furthermore, FT poses difficulty when there are missing data in the time domain. This occurs because of reduction of the acquisition time and consequently also in the number of acquired points, or because of artifacts during acquisition, or even intentional exclusion of the first signal points for the elimination of broad resonances that are producing the distorted baseline in the frequency domain. In this study, we propose the use of the Krylov Basis Diagonalization Method (KBDM) formalism as an alternative to some of FT limitations. The method adjusts signals of Free Induction Decay (FID) experiments with a sum of complex harmonic functions, exponentially damped, allowing easy manipulation of its characterization parameters. The KBDM is numerically more effective for truncated signal analysis and has several features that make it possible to remove peaks more efficiently, such as the residual water peak. Moreover, we introduced the possibility of quantification of MRS data with the described method. To evaluate the sensitivity, efficiency and reproducibility of the method for quantifying and analyzing truncated signals, and through the clinical spectra simulations and experiments in phantoms that would represent the brain metabolic environment, we proposed to perform proton MRS at different noise levels and with small variations of N- acetyl aspartate (NAA) metabolite. These studies allowed to prove the feasibility of the method to process MRS data and verified its potential in complementing techniques currently employed, especially when a greater temporal and spectral resolution is required, more than the limit imposed by the Uncertainty Relation of FT formalism. Furthermore, it is also a desirable effortless tool of handling specific peaks (e.g., exclusion and quantification). Exciting prospects from this work include the introduction of KBDM as an efficient and adjuvant technique to functional Magnetic Resonance Imaging (fMRI), for studying the brain functions, in MRS sequence to identify rapid variation in spectroscopic lines associated to metabolic activities in the brain.
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Beuchler, Sven. „Wavelet preconditioners for the p-version of the fem“. Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200600607.
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In this paper, we consider domain decomposition preconditioners for a system of linear algebraic equations arising from the p-version of the fem. We propose several multi-level preconditioners for the Dirichlet problems in the sub-domains in two and three dimensions. It is proved that the condition number of the preconditioned system is bounded by a constant independent of the polynomial degree. The proof uses interpretations of the p-version element stiffness matrix and mass matrix on [-1,1] as h-version stiffness matrix and weighted mass matrix. The analysis requires wavelet methods.
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Eibner, Tino, und Jens Markus Melenk. „A local error analysis of the boundary concentrated FEM“. Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601440.
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The boundary concentrated finite element method is
a variant of the hp-version of the FEM that is
particularly suited for the numerical treatment of
elliptic boundary value problems with smooth
coefficients and boundary conditions with low
regularity or non-smooth geometries. In this paper
we consider the case of the discretization of a
Dirichlet problem with exact solution
$u \in H^{1+\delta}(\Omega)$ and investigate the
local error in various norms. We show that for
a $\beta > 0$ these norms behave as
$O(N^{−\delta−\beta})$, where $N$ denotes the
dimension of the underlying finite element space.
Furthermore, we present a new Gauss-Lobatto based
interpolation operator that is adapted to the
case non-uniform polynomial degree distributions.
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Kåhlman, Niklas. „Summation By Parts Finite Difference Methods with Simultaneous Approximation Terms for the Heat Equation with Discontinuous Coefficients“. Thesis, Linnéuniversitetet, Institutionen för matematik (MA), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-84777.
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In this thesis we will investigate how the SBP-SAT finite difference method behave with and without an interface. As model problem, we consider the heat equation with piecewise constant coefficients. The thesis is split in two main parts. In the first part we look at the heat equation in one-dimension, and in the second part we expand the problem to a two-dimensional domain. We show how the SAT-parameters are chosen such that the scheme is dual consistent and stable. Then, we perform numerical experiments, now looking at the static case. In the one-dimensional case we see that the second order SBP-SAT method with an interface converge with an order of two, while the second order SBP-SAT method without an interface converge with an order of one.
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Karlsson, Christian. „A comparison of two multilevel Schur preconditioners for adaptive FEM“. Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-219939.
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There are several algorithms for solving the linear system of equations that arise from the finite element method with linear or near-linear computational complexity. One way is to find an approximation of the stiffness matrix that is such that it can be used in a preconditioned conjugate residual method, that is, a preconditioner to the stiffness matrix. We have studied two preconditioners for the conjugate residual method, both based on writing the stiffness matrix in block form, factorising it and then approximating the Schur complement block to get a preconditioner. We have studied the stationary reaction-diffusion-advection equation in two dimensions. The mesh is refined adaptively, giving a hierarchy of meshes. In the first method the Schur complement is approximated by the stiffness matrix at one coarser level of the mesh, in the second method it is approximated as the assembly of local Schur complements corresponding to macro triangles. For two levels the theoretical bound of the condition number is 1/(1-C²) for either method, where C is the Cauchy-Bunyakovsky-Schwarz constant. For multiple levels there is less theory. For the first method it is known that the condition number of the preconditioned stiffness matrix is O(l²), where l is the number of levels of the preconditioner, or, equivalently, the number mesh refinements. For the second method the asymptotic behaviour is not known theoretically. In neither case is the dependency of the condition number of C known. We have tested both methods on several problems and found the first method to always give a better condition number, except for very few levels. For all tested problems, using the first method it seems that the condition number is O(l), in fact it is typically not larger than Cl. For the second method the growth seems to be superlinear.
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Alsuleimanagha, Zaid, und Jing Liang. „Dynamic analysis of the Baozhusi dam using FEM“. Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171817.
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High magnitude earthquakes have devastating effects that leads to severe human and material losses; when affecting concrete gravity dams, seisms devastate the surrounding habitat through sudden release of reservoir. Dam safety is therefore a significant issue to be accounted in order to prevent the failure of dams located in seismic regions. The Baozhusi dam, the case study of this thesis, was exposed to 8.0 Ms (at the Mercalli scale) Wenchuan earthquake 2008 with intensity of (0.148 g) at the dam site. The earthquake intensity exceeded the design level of the dam (0.1 g); yet, the Baozhusi dam was not severely damaged as showed by tests. The present study case is a modeling and analyzing of the dynamical behavior of the Baozhusi dam during the earthquake duration. The results show that the horizontal component of the ground motion predominate the dynamic response of the dam. It is confirmed that the horizontal component of the ground motion crossed the dam at its axis and therefore minimizing the damages on the concrete gravity dam.
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Renardy, Marissa. „Analysis of the BiCG Method“. Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/50922.
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The Biconjugate Gradient (BiCG) method is an iterative Krylov subspace method that utilizes a 3-term recurrence. BiCG is the basis of several very popular methods, such as BiCGStab. The short recurrence makes BiCG preferable to other Krylov methods because of decreased memory usage and CPU time. However, BiCG does not satisfy any optimality conditions and it has been shown that for up to n/2-1 iterations, a special choice of the left starting vector can cause BiCG to follow {em any} 3-term recurrence. Despite this apparent sensitivity, BiCG often converges well in practice. This paper seeks to explain why BiCG converges so well, and what conditions can cause BiCG to behave poorly. We use tools such as the singular value decomposition and eigenvalue decomposition to establish bounds on the residuals of BiCG and make links between BiCG and optimal Krylov methods.
Master of Science
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Grasso, Eva. „Modelling visco-elastic seismic wave propagation : a fast-multipole boundary element method and its coupling with finite elements“. Phd thesis, Université Paris-Est, 2012. http://tel.archives-ouvertes.fr/tel-00730752.
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The numerical simulation of elastic wave propagation in unbounded media is a topical issue. This need arises in a variety of real life engineering problems, from the modelling of railway- or machinery-induced vibrations to the analysis of seismic wave propagation and soil-structure interaction problems. Due to the complexity of the involved geometries and materials behavior, modelling such situations requires sophisticated numerical methods. The Boundary Element method (BEM) is a very effective approach for dynamical problems in spatially-extended regions (idealized as unbounded), especially since the advent of fast BEMs such as the Fast Multipole Method (FMM) used in this work. The BEM is based on a boundary integral formulation which requires the discretization of the only domain boundary (i.e. a surface in 3-D) and accounts implicitly for the radiation conditions at infinity. As a main disadvantage, the BEM leads a priori to a fully-populated and (using the collocation approach) non-symmetrical coefficient matrix, which make the traditional implementation of this method prohibitive for large problems (say O(106) boundary DoFs). Applied to the BEM, the Multi-Level Fast Multipole Method (ML-FMM) strongly lowers the complexity in computational work and memory that hinder the classical formulation, making the ML-FMBEM very competitive in modelling elastic wave propagation. The elastodynamic version of the Fast Multipole BEM (FMBEM), in a form enabling piecewise-homogeneous media, has for instance been successfully used to solve seismic wave propagation problems in a previous work (thesis dissertation of S. Chaillat, ENPC, 2008). This thesis aims at extending the capabilities of the existing frequency-domain elastodynamic FMBEM in two directions. Firstly, the time-harmonic elastodynamic ML-FMBEM formulation has been extended to the case of weakly dissipative viscoelastic media. Secondly, the FMBEM and the Finite Element Method (FEM) have been coupled to take advantage of the versatility of the FEM to model complex geometries and non-linearities while the FM-BEM accounts for wave propagation in the surrounding unbounded medium. In this thesis, we consider two strategies for coupling the FMBEM and the FEM to solve three-dimensional time-harmonic wave propagation problems in unbounded domains. The main idea is to separate one or more bounded subdomains (modelled by the FEM) from the complementary semi-infinite viscoelastic propagation medium (modelled by the FMBEM) through a non-overlapping domain decomposition. Two coupling strategies have been implemented and their performances assessed and compared on several examples
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Simeitis, Sven D. „Vergleich von Simulationen mittels Pro/MECHANICA und ANSYS“. Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-68443.
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Gegenstand dieser Arbeit ist es, Simulationsergebnisse von Pro/MECHANICA und ANSYS zu vergleichen, um somit einen Hinweis auf die Qualität der Berechnungsergebnisse von integrierten FEM-Systemen zu bekommen. Als Beispiele dienen verschiedene Bauteile aus dem Gebiet der Strukturmechanik (linear-elastischer Bereich), welche mit Pro/MECHANICA und ANSYS modelliert und berechnet werden. Abschließend erfolgt eine Gegenüberstellung der Daten aus FEM und analytischer Rechnung, sowie eine Bewertung der Ergebnisse.
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Donner, Hendrik. „FEM-basierte Modellierung stark anisotroper Hybridcord-Elastomer-Verbunde“. Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-229188.
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Zur Analyse der Beanspruchungen in textilverstärkten Elastomerbauteilen wie Luftfedern, Reifen, Riemen und Schläuchen sind Berechnungsmodelle mit einer feinen Balance zwischen Genauigkeit und Effizienz erforderlich. Die großen Deformationen, stark anisotropen Struktureigenschaften und kleinen Abmessungen der Festigkeitsträger gegenüber denen des Bauteils bedürfen einerseits einer detaillierten Modellierung, andererseits sind die kritischen Bereiche in diesen Bauteilen räumlich stark begrenzt, sodass eine Reduktion des Berechnungsaufwands erstrebenswert ist. Diese Modellreduktion führt zu Simulationen mit geringer Rechenzeit, die für eine praxistaugliche Optimierung von Hybridcord-Elastomer-Verbunden unerlässlich sind. Die beiden Hauptschwerpunkte der vorliegenden Arbeit bilden die kontinuumsmechanische Modellierung von Hybridcorden und die Erstellung repräsentativer Volumenelemente hochbeanspruchter Hybridcord-Elastomer-Verbunde. Aufbauend auf einem anisotropen Plastizitätsmodell zur Erfassung der Reibung in Multifilamentgarnen stellt ein Finite-Elemente-Modell zur Simulation der Verzwirnung von Hybridcorden das Fundament der Arbeit dar. Anhand experimenteller Ergebnisse aus Zug- und Torsionsversuchen sowie einem Vergleich mit Querschnittsaufnahmen wird gezeigt, dass das Modell die komplexen Eigenschaften eines Hybridcords abbilden kann. Die Grundlage der repräsentativen Volumenelemente stellt eine Erweiterung der klassischen periodischen Randbedingungen dar, die eine Berücksichtigung von Krümmungen und Drucklasten ermöglicht. Das Modell eignet sich daher, die Beanspruchungen in den hochbelasteten Bereichen textilverstärkter Elastomerbauteile wie der Rollfalte einer Luftfeder effizient zu analysieren. Mittels Parameterstudien werden abschließend Hybridcorde und Hybridcord-Elastomer-Verbunde untersucht und einige Hinweise für eine optimale Gestaltung hinsichtlich minimaler Beanspruchungen des Elastomers, des Hybridcords sowie der Grenzfläche gegebenThe analysis of stresses and strains within textile-reinforced rubber components like air springs, tyres, driving belts, and tubes requires accurate as well as efficient computational models. On the one hand, the large deformations, the composite's strongly anisotropic properties, and the large ratio between the size of the cords and the composite necessitate a precise modeling. On the other hand, the highly loaded parts of the components are spatially confined and thus a reduction of the computational effort is desirable. These reduced models are efficient enough for performing engineering-oriented optimizations. The two main priorities of this work are the continuum mechanical modeling of hybrid cords and the development of representative volume elements of highly loaded hybrid cord-rubber composites. Based on an anisotropic plasticity model, which takes the frictional sliding between the filaments within multifilament yarns into account, a finite element model for the simulation of the twisting process of a hybrid cord is the fundament of this work. A comparison with experimental results from tensile and torsional tests as well as images of cross sections validate the proposed hybrid cord model. The basis of the representative volume element is the extension of the classical periodic boundary conditions, which now enable to take the curvature and pressure load into account. Thus, the model is suitable to analyze the highly loaded parts of hybrid cord-rubber composites like the rolling lobe of an air spring. Finally, the set-ups of hybrid cords and hybrid cord-rubber composites are analyzed by means of parameter studies to obtain a minimized loading of the rubber, yarns, and their interface
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Holsten, Sven. „FEM-unterstützte Parameterstudie des Innengewinde-Fertigungsverfahrens Gewindefurchen“. Kassel : Kassel Univ. Press, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=981992331.
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Dostál, Tomáš. „Návrh ražby a primárního ostění tunelu na stavbě vysokorychlostního železničního spojení“. Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409747.
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As part of modernization of the Brno-Přerov railway line, is in the section between village Blažovice and town Vyškov desined tunnel composed of two monorail tubes about 640 meters length. Tubes are situated in neogenic clay with an overburden height of 11 meters. This master thesis deals with design suitable tunnel exavation, primary lining with static calculation and geotechnical monitoring.
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Lau, Sum-hung. „Adaptive FEM preprocessing for electro magnetic field analysis of electric machines /“. Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17505823.
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Kocak, Umut, Karljohan Palmerius und Matthew Cooper. „Dynamic Deformation Using Adaptable, Linked Asynchronous FEM Regions“. Linköpings universitet, Visuell informationsteknologi och applikationer, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-18053.
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In order to simulate both physically and visually realistic soft tissuedeformations, the Finite Element Method (FEM) is the mostpopular choice in the literature. However it is non-trivial to modelcomplex behaviour of soft tissue with sufficient refresh rates, especiallyfor haptic force feedback which requires an update rate ofthe order of 1 kHz. In this study the use of asynchronous regions isproposed to speed up the solution of FEM equations in real-time. Inthis way it is possible to solve the local neighborhood of the contactwith high refresh rates, while evaluating the more distant regions atlower frequencies, saving computational power to model complexbehaviour within the contact area. Solution of the different regionsusing different methods is also possible. To attain maximum efficiencythe size of the regions can be changed, in real-time, in responseto the size of the deformation.
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Eibner, Tino, und Jens Markus Melenk. „Multilevel preconditioning for the boundary concentrated hp-FEM“. Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601662.
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The boundary concentrated finite element method
is a variant of the hp-version of the finite
element method that is particularly suited for
the numerical treatment of elliptic boundary
value problems with smooth coefficients and low
regularity boundary conditions. For this method
we present two multilevel preconditioners that
lead to preconditioned stiffness matrices with
condition numbers that are bounded uniformly in
the problem size N. The cost of applying the
preconditioners is O(N). Numerical examples
illustrate the efficiency of the algorithms.
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Lindqvist, Petter. „Validering av solida temperaturer i FDS genom jämförelse mot FE-beräkningar“. Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79973.
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FDS (Fire Dynamics Simulator) använder en version av Navier-Stokes ekvationerna för att göra noggranna beräkningar av värme- och gastransport genom brandbelastade utrymmen. Utvecklarna av programmet arbetar kontinuerligt med att validera det allteftersom nya funktioner tillförs för att öka noggrannheten och bredda tillämpningsområdena. Väldigt lite av detta arbete fokuserar dock på FDS:s konduktionsmodell, den endimensionella Crank-Nicolson metoden. Det här examensarbetet ämnar därför undersöka noggrannheten i FDS:s konduktionsmodell genom jämförelse mot beräkningar med FEM (Finita elementmetoden). En FDS-modell skapades för att tillåta undersökning av en vägg och dess randvillkor med så liten påverkan från andra faktorer som möjligt. Detta för att skapa en kontrollerad omgivning som enkelt kunde replikeras i efterföljande FE-beräkningar av det konduktiva värmeflödet genom den solida obstruktionen. Tre väggar (10 cm betong, 20 cm betong och 1 mm stål) vardera med tre randvillkor (Exposed, Void och Insulated) utsattes för tre temperaturer (100 °C, 500 °C och 1000 °C) vilket ger 27 FDS simuleringar. Den adiabatiska yttemperaturen mättes i varje simulering och användes som indata till motsvarande FE-beräkningar. Resultatet påvisade inga signifikanta motsägelser vad gäller randvillkoren, med tillräcklig tid för termisk penetrering påverkade de den resulterande temperaturen som väntat. Undantaget var en mindre avvikelse i stålväggarna som utsattes för 100 °C och 500 °C med randvillkoren Exposed och Void där FDS aningen underskattade temperaturen relativt FE-beräkningarna. Gastemperaturerna i gridcellerna närmast väggen visade sig vara opålitliga. De tenderade att genomgå substantiella fluktuationer, troligen som ett resultat av hur FDS hanterar diskretiseringen av icke-solida volymer för Navier-Stokes beräkningarna. Dessa fluktuationer påverkade dock inte de resulterande solida temperaturerna eftersom medelgastemperaturen var korrekt. FDS påvisades även ha en tendens att aningen överskatta yttemperaturen under de första minuterna av simuleringarna relativt FE-beräkningarna. Temperaturerna från de två beräkningsmetoderna konvergerade dock efter några få minuter i samtliga tester. Dessa avvikelser ansågs ha för liten påverkan på de solida temperaturerna för att påvisa onoggrannhet i FDS. Därmed drogs slutsatsen att FDS:s beräkningar av temperaturer i solida material är tillräckligt noggranna inom dessa avgränsningar.FDS (Fire Dynamics Simulator) uses a version of the Navier-Stokes equations to make accurate calculations of heat and gas flow through enclosures exposed to fire. The developers of FDS have, and continue to, validate it as new features get added in an attempt to increase its accuracy and broaden its potential applications. However, little of this effort is focused on FDS’ conductive heat transfer model, based on the one-dimensional Crank-Nicolson method. Thus, this study aims to test the accuracy of FDS’ conduction model by comparing it to calculations using FEM (Finite Element Method). FDS simulations were created so as to facilitate the study of a wall and its boundary conditions with as little interference from other factors as possible. This to create a controlled environment which easily could be replicated in the subsequent FE-calculations of the conductive heat flow through the solid obstructions. Three different walls (10 cm concrete, 20 cm concrete and 1 mm steel), each with the three different boundary conditions for the rear surface (Exposed, Void and Insulated), were exposed to three different temperatures (100 °C, 500 °C and 1000 °C) for a total of 27 FDS simulations. The adiabatic surface temperature was measured in each simulation in FDS and used as input for the corresponding FE-calculations. The results showed no clear inconsistencies in the boundary conditions, given enough time for thermal penetration they affected the resulting temperatures as expected. Save a slight deviation in the steel walls exposed to 100 °C and 500 °C with boundary conditions Exposed and Void where FDS slightly underestimated the temperature relative to the FE-calculations. The gas temperatures in the grid cells closest to the wall were found to be unreliable as they tended to undergo substantial fluctuations, likely as a result of how FDS handles the discretization of non-solid space for the Navier-Stokes calculations. These fluctuations were however not found to affect the solid temperatures as the mean gas temperature was accurate. FDS was also found to have a tendency to slightly overestimate the surface temperature in the first few minutes of the simulations relative to the FE-calculations. Though the resulting temperatures from the two methods converged after a few minutes at most in all tests. These deviations were considered to have too minor an impact on the solid temperature to justify claims of inaccuracy in FDS. Thus, the general conclusion of this study is that FDS’ predictions of solid phase temperatures are sufficiently accurate within these delimitations.
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Banihashemi, Seyed Parsa. „Parallel explicit FEM algorithms using GPU's“. Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54391.
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The Explicit Finite Element Method is a powerful tool in nonlinear dynamic finite element analysis. Recent major developments in computational devices, in particular, General Purpose Graphical Processing Units (GPGPU's) now make it possible to increase the performance of the explicit FEM.
This dissertation investigates existing explicit finite element method algorithms which are then redesigned for GPU's and implemented. The performance of these algorithms is assessed and a new asynchronous variational integrator spatial decomposition (AVISD) algorithm is developed which is flexible and encompasses all other methods and can be tuned based for a user-defined problem and the performance of the user's computer.
The mesh-aware performance of the proposed explicit finite element algorithm is studied and verified by implementation. The current research also introduces the use of a Particle Swarm Optimization method to tune the performance of the proposed algorithm automatically given a finite element mesh and the performance characteristics of a user's computer. For this purpose, a time performance model is developed which depends on the finite element mesh and the machine performance. This time performance model is then used as an objective function to minimize the run-time cost.
Also, based on the performance model provided in this research and predictions about the changes in GPU's in the near future, the performance of the AVISD method is predicted for future machines. Finally, suggestions and insights based on these results are proposed to help facilitate future explicit FEM development.
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Ferreira, Vitor Maciel Vilela. „A hybrid les / lagrangian fdf method on adaptive, block-structured mesh“. Universidade Federal de Uberlândia, 2015. https://repositorio.ufu.br/handle/123456789/14982.
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Fundação de Amparo a Pesquisa do Estado de Minas GeraisEsta dissertação é parte de um amplo projeto de pesquisa, que visa ao desenvolvimento de uma plataforma computacional de dinâmica dos fluidos (CFD) capaz de simular a física de escoamentos que envolvem mistura de várias espécies químicas, com reação e combustão, utilizando um método hibrido Simulação de Grandes Escalas (LES) / Função Densidade Filtrada (FDF) Lagrangiana em malha adaptativa, bloco-estruturada. Uma vez que escoamentos com mistura proporcionam fenômenos que podem ser correlacionados com a combustão em escoamentos turbulentos, uma visão global da fenomenologia de mistura foi apresentada e escoamentos fechados, laminar e turbulento, que envolvem mistura de duas espécies químicas inicialmente segregadas foram simulados utilizando o código de desenvolvimento interno AMR3D e o código recentemente desenvolvido FDF Lagrangiana de composição. A primeira etapa deste trabalho consistiu na criação de um modelo computacional de partículas estocásticas em ambiente de processamento distribuído. Isto foi alcançado com a construção de um mapa Lagrangiano paralelo, que pode gerenciar diferentes tipos de elementos lagrangianos, incluindo partículas estocásticas, particulados, sensores e nós computacionais intrínsecos dos métodos Fronteira Imersa e Acompanhamento de Interface. O mapa conecta informações Lagrangianas com a plataforma Euleriana do código AMR3D, no qual equações de trans- porte são resolvidas. O método FDF Lagrangiana de composição realiza cálculos algébricos sobre partículas estocásticas e provê campos de composição estatisticamente equivalentes aos obtidos quando se utiliza o método de Diferenças Finitas para solução de equações diferenciais parciais; a técnica de Monte Carlo foi utilizada para resolver um sistema derivado de equações diferenciais estocásticas (SDE). Os resultados concordaram com os benchmarks, que são simulações baseadas em plataforma de Diferenças Finitas para solução de uma equação de transporte de composição filtrada.
This master thesis is part of a wide research project, which aims at developing a com- putational fluid dynamics (CFD) framework able to simulate the physics of multiple-species mixing flows, with chemical reaction and combustion, using a hybrid Large Eddy Simulation (LES) / Lagrangian Filtered Density Function (FDF) method on adaptive, block-structured mesh. Since mixing flows provide phenomena that may be correlated with combustion in turbulent flows, we expose an overview of mixing phenomenology and simulated enclosed, ini- tially segregated two-species mixing flows, at laminar and turbulent states, using the in-house built AMR3D and the developed Lagrangian composition FDF codes. The first step towards this objective consisted of building a computational model of notional particles transport on distributed processing environment. We achieved it constructing a parallel Lagrangian map, which can hold different types of Lagrangian elements, including notional particles, particu- lates, sensors and computational nodes intrinsic to Immersed Boundary and Front Tracking methods. The map connects Lagrangian information with the Eulerian framework of the AMR3D code, in which transport equations are solved. The Lagrangian composition FDF method performs algebraic calculations over an ensemble of notional particles and provides composition fields statistically equivalent to those obtained by Finite Differences numerical solution of partially differential equations (PDE); we applied the Monte Carlo technique to solve a derived system of stochastic differential equations (SDE). The results agreed with the benchmarks, which are simulations based on Finite Differences framework to solve a filtered composition transport equation.
Mestre em Engenharia Mecânica
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Bewick, Bryan T. „A combined FEM and MPM simulation of impact-resistant design /“. free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1422910.
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Eibner, Tino, und Jens Markus Melenk. „p-FEM quadrature error analysis on tetrahedra“. Universitätsbibliothek Chemnitz, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200702059.
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In this paper we consider the p-FEM for elliptic boundary value problems on tetrahedral meshes where the entries of the stiffness matrix are evaluated by numerical quadrature. Such a quadrature can be done by mapping the tetrahedron to a hexahedron via the Duffy transformation.
We show that for tensor product Gauss-Lobatto-Jacobi quadrature formulas with q+1=p+1 points in each direction and shape functions that are adapted to the quadrature formula, one again has discrete stability for the fully discrete p-FEM.
The present error analysis complements the work [Eibner/Melenk 2005] for the p-FEM on triangles/tetrahedra where it is shown that by adapting the shape functions to the quadrature formula, the stiffness matrix can be set up in optimal complexity.
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Lezar, Evan. „hp-Adaptation for the FEM Analysis of Waveguides“. Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/1335.
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Churý, Tomáš. „Stanovení modálních charakteristik celokompozitového křídla s využitím MKP metod“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232093.
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The diploma thesis deals with the creation of a detail FEM model all-composite wing of glider. Reduction created FEM model of the beam model. The models are calculated natural frequencies, vibration shapes wings and then subsequently compared the results of analyzes of both models.
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Kennedy, Deniz. „Level Set Methods for Two-Phase Flows with FEM“. Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-238163.
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Two-phase flows is a branch of multiphase flows. The aim of the project is to implement two different level set methods and analyse and compare the numerical results. The level set method is used in order to represent the behaviour of the interface between two incompressible fluids in a flow. Reinitialization is a method to straighten a distorted shape of the level set function that might be caused by the numerical solution of the convection equation and/or by the complicated fluid velocity fields. The main purpose of reinitialization is to preserve the level set function, and thus the shape of the interface as much as possible throughout the simulation. In order to avoid the oscillations, the stationary weak form is approximated with Galerkin Least Squares (GLS) finite element instead of standard finite element approximation. In order to create the velocity field of the incompressible fluid for the benchmark case, the Stokes equations are solved. The stability has to be measured carefully as it has imbalance between space stability and time stability as well as with the reinitialization. The convergence rates in the numerical results for the both experiment and benchmark cases show that reinitializations usually give a better result. Further researches for this paper could be using another FEM stabilization method, which is other than GLS, in order to solve the stabilization problem in 2D.
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Lins, Rafael Marques. „A posteriori error estimations for the generalized finite element method and modified versions“. Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-03092015-083839/.
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This thesis investigates two a posteriori error estimators, based on gradient recovery, aiming to fill the gap of the error estimations for the Generalized FEM (GFEM) and, mainly, its modified versions called Corrected XFEM (C-XFEM) and Stable GFEM (SGFEM). In order to reach this purpose, firstly, brief reviews regarding the GFEM and its modified versions are presented, where the main advantages attributed to each numerical method are highlighted. Then, some important concepts related to the error study are presented. Furthermore, some contributions involving a posteriori error estimations for the GFEM are shortly described. Afterwards, the two error estimators hereby proposed are addressed focusing on linear elastic fracture mechanics problems. The first estimator was originally proposed for the C-XFEM and is hereby extended to the SGFEM framework. The second one is based on a splitting of the recovered stress field into two distinct parts: singular and smooth. The singular part is computed with the help of the J integral, whereas the smooth one is calculated from a combination between the Superconvergent Patch Recovery (SPR) and Singular Value Decomposition (SVD) techniques. Finally, various numerical examples are selected to assess the robustness of the error estimators considering different enrichment types, versions of the GFEM, solicitant modes and element types. Relevant aspects such as effectivity indexes, error distribution and convergence rates are used for describing the error estimators. The main contributions of this thesis are: the development of two efficient a posteriori error estimators for the GFEM and its modified versions; a comparison between the GFEM and its modified versions; the identification of the positive features of each error estimator and a detailed study concerning the blending element issues.Esta tese investiga dois estimadores de erro a posteriori, baseados na recuperação do gradiente, visando preencher o hiato das estimativas de erro para o Generalized FEM (GFEM) e, sobretudo, suas versões modificadas denominadas Corrected XFEM (C-XFEM) e Stable GFEM (SGFEM). De modo a alcançar este objetivo, primeiramente, breves revisões a respeito do GFEM e suas versões modificadas são apresentadas, onde as principais vantagens atribuídas a cada método são destacadas. Em seguida, alguns importantes conceitos relacionados ao estudo do erro são apresentados. Além disso, algumas contribuições envolvendo estimativas de erro a posteriori para o GFEM são brevemente descritas. Posteriormente, os dois estimadores de erro propostos neste trabalho são abordados focando em problemas da mecânica da fratura elástico linear. O primeiro estimador foi originalmente proposto para o C-XFEM e por este meio é estendido para o âmbito do SGFEM. O segundo é baseado em uma divisão do campo de tensões recuperadas em duas partes distintas: singular e suave. A parte singular é calculada com o auxílio da integral J, enquanto que a suave é calculada a partir da combinação entre as técnicas Superconvergent Patch Recovery (SPR) e Singular Value Decomposition (SVD). Finalmente, vários exemplos numéricos são selecionados para avaliar a robustez dos estimadores de erro considerando diferentes tipos de enriquecimento, versões do GFEM, modos solicitantes e tipos de elemento. Aspectos relevantes tais como índices de efetividade, distribuição do erro e taxas de convergência são usados para descrever os estimadores de erro. As principais contribuições desta tese são: o desenvolvimento de dois eficientes estimadores de erro a posteriori para o GFEM e suas versões modificadas; uma comparação entre o GFEM e suas versões modificadas; a identificação das características positivas de cada estimador de erro e um estudo detalhado sobre a questão dos elementos de mistura.
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Fu, Tuan-Chun. „FEM simulation of ultrasonic wave propagation in solid rods“. Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3452.
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Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains x, 82 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 80-81).
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Witkowski, Thomas. „Software concepts and algorithms for an efficient and scalable parallel finite element method“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-141651.
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Software packages for the numerical solution of partial differential equations (PDEs) using the finite element method are important in different fields of research. The basic data structures and algorithms change in time, as the user\'s requirements are growing and the software must efficiently use the newest highly parallel computing systems. This is the central point of this work. To make efficiently use of parallel computing systems with growing number of independent basic computing units, i.e.~CPUs, we have to combine data structures and algorithms from different areas of mathematics and computer science. Two crucial parts are a distributed mesh and parallel solver for linear systems of equations. For both there exists multiple independent approaches. In this work we argue that it is necessary to combine both of them to allow for an efficient and scalable implementation of the finite element method. First, we present concepts, data structures and algorithms for distributed meshes, which allow for local refinement. The central point of our presentation is to provide arbitrary geometrical information of the mesh and its distribution to the linear solver. A large part of the overall computing time of the finite element method is spend by the linear solver. Thus, its parallelization is of major importance. Based on the presented concept for distributed meshes, we preset several different linear solver methods. Hereby we concentrate on general purpose linear solver, which makes only little assumptions about the systems to be solver. For this, a new FETI-DP (Finite Element Tearing and Interconnect - Dual Primal) method is proposed. Those the standard FETI-DP method is quasi optimal from a mathematical point of view, its not possible to implement it efficiently for a large number of processors (> 10,000). The main reason is a relatively small but globally distributed coarse mesh problem. To circumvent this problem, we propose a new multilevel FETI-DP method which hierarchically decompose the coarse grid problem. This leads to a more local communication pattern for solver the coarse grid problem and makes it possible to scale for a large number of processors. Besides the parallelization of the finite element method, we discuss an approach to speed up serial computations of existing finite element packages. In many computations the PDE to be solved consists of more than one variable. This is especially the case in multi-physics modeling. Observation show that in many of these computation the solution structure of the variables is different. But in the standard finite element method, only one mesh is used for the discretization of all variables. We present a multi-mesh finite element method, which allows to discretize a system of PDEs with two independently refined meshesSoftwarepakete zur numerischen Lösung partieller Differentialgleichungen mit Hilfe der Finiten-Element-Methode sind in vielen Forschungsbereichen ein wichtiges Werkzeug. Die dahinter stehenden Datenstrukturen und Algorithmen unterliegen einer ständigen Neuentwicklung um den immer weiter steigenden Anforderungen der Nutzergemeinde gerecht zu werden und um neue, hochgradig parallel Rechnerarchitekturen effizient nutzen zu können. Dies ist auch der Kernpunkt dieser Arbeit. Um parallel Rechnerarchitekturen mit einer immer höher werdenden Anzahl an von einander unabhängigen Recheneinheiten, z.B.~Prozessoren, effizient Nutzen zu können, müssen Datenstrukturen und Algorithmen aus verschiedenen Teilgebieten der Mathematik und Informatik entwickelt und miteinander kombiniert werden. Im Kern sind dies zwei Bereiche: verteilte Gitter und parallele Löser für lineare Gleichungssysteme. Für jedes der beiden Teilgebiete existieren unabhängig voneinander zahlreiche Ansätze. In dieser Arbeit wird argumentiert, dass für hochskalierbare Anwendungen der Finiten-Elemente-Methode nur eine Kombination beider Teilgebiete und die Verknüpfung der darunter liegenden Datenstrukturen eine effiziente und skalierbare Implementierung ermöglicht. Zuerst stellen wir Konzepte vor, die parallele verteile Gitter mit entsprechenden Adaptionstrategien ermöglichen. Zentraler Punkt ist hier die Informationsaufbereitung für beliebige Löser linearer Gleichungssysteme. Beim Lösen partieller Differentialgleichung mit der Finiten Elemente Methode wird ein großer Teil der Rechenzeit für das Lösen der dabei anfallenden linearen Gleichungssysteme aufgebracht. Daher ist deren Parallelisierung von zentraler Bedeutung. Basierend auf dem vorgestelltem Konzept für verteilten Gitter, welches beliebige geometrische Informationen für die linearen Löser aufbereiten kann, präsentieren wir mehrere unterschiedliche Lösermethoden. Besonders Gewicht wird dabei auf allgemeine Löser gelegt, die möglichst wenig Annahmen über das zu lösende System machen. Hierfür wird die FETI-DP (Finite Element Tearing and Interconnect - Dual Primal) Methode weiterentwickelt. Obwohl die FETI-DP Methode vom mathematischen Standpunkt her als quasi-optimal bezüglich der parallelen Skalierbarkeit gilt, kann sie für große Anzahl an Prozessoren (> 10.000) nicht mehr effizient implementiert werden. Dies liegt hauptsächlich an einem verhältnismäßig kleinem aber global verteilten Grobgitterproblem. Wir stellen eine Multilevel FETI-DP Methode vor, die dieses Problem durch eine hierarchische Komposition des Grobgitterproblems löst. Dadurch wird die Kommunikation entlang des Grobgitterproblems lokalisiert und die Skalierbarkeit der FETI-DP Methode auch für große Anzahl an Prozessoren sichergestellt. Neben der Parallelisierung der Finiten-Elemente-Methode beschäftigen wir uns in dieser Arbeit mit der Ausnutzung von bestimmten Voraussetzung um auch die sequentielle Effizienz bestehender Implementierung der Finiten-Elemente-Methode zu steigern. In vielen Fällen müssen partielle Differentialgleichungen mit mehreren Variablen gelöst werden. Sehr häufig ist dabei zu beobachten, insbesondere bei der Modellierung mehrere miteinander gekoppelter physikalischer Phänomene, dass die Lösungsstruktur der unterschiedlichen Variablen entweder schwach oder vollständig voneinander entkoppelt ist. In den meisten Implementierungen wird dabei nur ein Gitter zur Diskretisierung aller Variablen des Systems genutzt. Wir stellen eine Finite-Elemente-Methode vor, bei der zwei unabhängig voneinander verfeinerte Gitter genutzt werden können um ein System partieller Differentialgleichungen zu lösen
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O, Chol Gyu. „Shape optimization for Two-Dimensional transonic airfoil by using the coupling of FEM and BEM“. [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-26978.
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Ridane, Nader. „FEM-gestützte Prozessregelung des Freibiegens /“. Aachen : Shaker, 2008. http://d-nb.info/989460258/04.
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Bedoya, Cervera Jose Julian. „Stent design and arterial mechanics: parameterization tools using the finite element method“. Texas A&M University, 2003. http://hdl.handle.net/1969.1/5812.
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Vascular stents are medical devices used to treat stenoses blockages in arteries
that restrict blood flow. Most commonly, stents are made out of stainless steel or nitinol,
and are delivered to the afflicted sites via catheter-based delivery systems. Usually, stents
are balloon-expandable or self-expanding. In order for the treated vessel to remain
patent, it is necessary that the stents be oversized to prevent flow-induced or pressureinduced
stent migration. Furthermore, stents must be rigid enough to prevent the collapse
of the vessel, allowing the free passage of blood. However, it has been observed that the
presence of the stent in the artery triggers adverse biological responses such as neointinal
hyperplasia, often times culminating in restenosis. Extensive research external to this
investigation has elucidated evidence to suggest that the abnormally high stresses
imparted to the arterial wall as a result of stenting are an important factor in the treatment
and development of cardiovascular diseases. Furthermore, normal physiologic diameter
flcutuations between systole and diastole produce beneficial biological responses in the
artery wall. The primary purpose of this study was to investigate specific stent design
criteria that minimize the stress field in the arterial wall to mitigate the impact of
restenosis. Commerically available finite element software was used to design the stents parametrically, and perform the stress analysis on a hyperelastic arterial model, including
the effects of contact between the artery and stent. Seven stent geometries were uniquely
defined by varying strut-spacing, ring amplitude, and crown radii of curvature. Stent
designs with large strut spacing, large ring amplitude and a greater than zero radius of
curvature imparted the less severe stress field in the arterial wall as well as maximizing
vessel deflection between systole and diastole. In contrast, stents with small strut
spacing, small amplitudes and zero radius of curvature at the crowns imparted
significantly higher stresses. The small strut spacing and small amplitude created stiffer
stents, prventing the artery from experiencing physiologic diameter fluctuations between
systole and diastole. Evidence presented herein suggests that strut spacing should be as
wide as possible without causing pillowing of the arterial wall into the stent.
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Eibner, Tino. „Randkonzentrierte und adaptive hp-FEM“. Doctoral thesis, Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601050.
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Die vorliegende Arbeit befasst sich mit verschiedenen Aspekten der hp-FEM.
Insbesondere werden hierbei folgende Punkte genauer untersucht:
1. Das effiziente Aufstellen der Steifigkeitsmatrix auf Referenzelementen, die keine Tensorproduktstruktur besitzen.
2. Eine lokale Konvergenzbetrachtung für die randkonzentrierte hp-FEM.
3. Ein Multilevel-Löser für die randkonzentrierte hp-FEM.
4. Eine Strategie für hp-Adaptivität.
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Davidsson, Johan. „Sobolev Spaces and the Finite Element Method“. Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-67470.
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In this essay we present the Sobolev spaces and some basic properties of them. The Sobolev spaces serve as a theoretical framework for studying solutions to partial differential equations. The finite element method is presented which is a numerical method for solving partial differential equations.
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Botha, Matthys Michiel. „Efficient finite element electromagnetic analysis of antennas and microwave devices : the FE-BI-FMM formulation and a posteriori error estimation for p adaptive analysis“. Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52818.
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Dissertation (PhD)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: This document presents a Galerkin FE formulation for the full-wave, frequency domain, electromagnetic analysis of three dimensional structures relevant to microwave engineering, together with the investigation of two techniques to enhance the formulation's computational efficiency. The first technique considered is the fast multi pole method (FMM) and the second technique is adaptive refinement of the discretization, based on a posteriori error estimation. Thus, the motivation for the work presented in this document is to increase the computational efficiency of the FE formulation considered. The FE formulation considered is widely used within the microwave engineering, finite element community. Tetrahedral, rectilinear, curl-conforming, mixed- and full order, hierarchical vector elements are used. The formulation is extended to incorporate a cavity backed aperture employing the appropriate half-space Green function within a BI boundary condition, which represents a specific member of a large class of hybrid FE-BI formulations. The formulation is also extended to model coaxial ports via a Neumann boundary condition, using a priori knowledge of the dominant modal fields. Results are presented in support of the formulation and its extensions, including novel results on the coupling between microstrip patch antennas on a perforated substrate. The FMM is investigated first, with the purpose of optimizing the non-local BI component of the cavity FE-BI formulation, in light of its coupling with the differential equation based, sparse FEM. The FMM results in a partly sparse factorization of the BI contribution to the system matrix. Error control schemes for the FMM are thoroughly reviewed and an additional, novel scheme is empirically devised. The second technique investigated, which is more directly related to the FEM and larger in scope, is the use of a posteriori error estimation, in order to optimize the FE discretization through adaptive refinement. A overview of available a posteriori error estimation techniques in the general FE literature is given as well as a survey of available techniques that are specifically tailored to Maxwell's equations. Two known approaches within the applied mathematics literature are adapted to the FE formulation at hand, resulting in two novel, residual based error estimation procedures for this FE formulation - one explicit in nature and the other implicit. The two error estimators are then used to drive a single p adaptive analysis cycle of the FE formulation, experimentally demonstrating their effectiveness. A quasi-static condition is introduced and successfully used to enhance the adaptive algorithm's effectiveness, independently of the error estimation procedure employed. The novel error estimation schemes and adaptive results represent the main research contributions of this study.
AFRIKAANSE OPSOMMING: Hierdie dokument beskryf 'n Galerkin eindige element (EE) formulering vir die volgolf, frekwensiegebied, elektromagnetiese analise van driedimensionele strukture relevant vir mikrogolfingenieurwese, saam met die ondersoek van twee tegnieke om die numeriese effektiwiteit van die formulering te verbeter. Die eerste tegniek wat ondersoek word, is die vinnige multipooi metode (VMM) en die tweede is die aanpasbare verfyning van die EE diskretisering, gebaseer op a posteriori foutberaming. Dus, die motivering vir hierdie werk is om die numeriese effektiwiteit van die genoemde EE formulering te verbeter. Die bogenoemde EE formulering word algemeen gebruik deur die mikrogolfingenieurswese, eindige element-gemeenskap. Tetrahedriese, reglynige, curl-ondersteunende, hierargiese vektorelemente van gemengde- en volledige ordes word gebruik. Die formulering word uitgebrei om holtes in 'n oneindige grondvlak te kan hanteer, deur gebruik te maak van die toepaslike Green funksie binne 'n grensintegraal (GI) grensvoorwaarde, wat 'n spesifieke lid is van 'n groot klas, hibriede, EE-GI formulerings. Die formulering word ook uitgebrei om koaksiale poorte to modelleer via 'n Neumann grensvoorwaarde, deur die gebruik van a priori kennis van die koaksiale, dominante modus-velde. Resultate word gelewer om die formulering, saam met die uitbreidings daarvan, te ondersteun, insluitende oorspronklike resultate in verband met die koppeling tussen mikrostrook plakantennes op 'n geperforeerde substraat. Die VMM word eerste ondersoek, met die doelom die nie-lokale, GI komponent van die EEGI formulering vir holtes te optimeer, weens die koppeling daarvan met die yl, differensiaalvergelyking- gebaseerde, eindige element-metode. Die VMM lei tot 'n gedeeltelik-yl faktorisering van die GI bydrae tot die algehele matriksvergelyking. Skemas om die VMM fout te beheer word deeglik ondersoek en 'n addisionele, oorspronklike skema word empiries ontwikkel. Die tweede tegniek wat ondersoek word, wat meer direk verband hou met die eindige elementmetode, en van groter omvang is, is die gebruik van a posteriori foutberaming om die EE diskretisasie te optimeer deur middel van aanpasbare verfyning. 'n Oorsig van beskikbare, a posteriori foutberamingstegnieke in die algemene EE literatuur word gegee, asook 'n opname van beskikbare tegnieke wat spesifiek gerig is op Maxwell se vergelykings. Twee bekende benaderings binne die toegepaste wiskunde-literatuur word aangepas by die bogenoemde EE formulering, wat lei tot twee oorspronklike residu-gebaseerde foutberamingstegnieke vir hierdie formulering - een van 'n eksplisiete aard en die ander implisiet. Die twee foutberamingstegnieke word gebruik om 'n enkel, p-aanpasbare analisesiklus aan te dryf, wat die effektiwiteit van die foutberamingstegnieke eksperimenteel demonstreer. 'n Kwasi-statiese vereiste word beskryf en suksesvol gebruik om die aanpasbare algoritme se effektiwiteit te verhoog, onafhanklik van die foutberamingstegniek wat gebruik word. Die oorspronklike foutberamingstegnieke en aanpasbare algoritme-resultate verteenwoordig die hoof navorsingsbydraes van hierdie studie.
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Ma, Hua. „Possibility of substituting FEM with theta method by modifying time derivative term“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ54725.pdf.
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Liu, Bo Yan. „Two-dimensional free vibration analysis of cracked FGM beams by Ritz method“. Thesis, University of Macau, 2015. http://umaclib3.umac.mo/record=b3335682.
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Zeng, Wei. „Advanced Development of Smoothed Finite Element Method (S-FEM) and Its Applications“. University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439309306.
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Ngo, Ngoc Son Civil & Environmental Engineering Faculty of Engineering UNSW. „Limit and shakedown analyses by the p-version fem“. Awarded by:University of New South Wales. Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/23463.
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This thesis provides a contribution towards a general procedure for solving robustly and efficiently limit and shakedown analyses of engineering structures within the static approach which has been chosen for its simplicity of implementation. Throughout the thesis, attempts at improving the robustness and efficiency of the computations are presented. Beginning with efforts to prevent volumetric locking, which is a severe shortcoming of traditional low order h-type displacement elements, the investigation proposes the use of the high order p-version of the finite element method. It is shown theoretically and confirmed numerically that this p-method is not only robust in preventing locking, but also provides very accurate results. However, the use of uniformly distributed high order p-elements may be computationally demanding when the size of the problem becomes large. This difficulty is tackled by two main approaches: use of a p-adaptive procedure at the elastic computation stage and use of approximate piecewise linear yield functions. The p-adaptive scheme produces a non-uniform p-distribution and helps to greatly reduce the number of degrees of freedom needed while still guaranteeing the required level of accuracy. The overall gain is that the sizes of the models are reduced significantly and hence also the computational effort. The adoption of piecewise linear yield surfaces helps to further increase the efficiency at the expense of possibly slightly less accurate, but still very acceptable, results. State-of-the-art linear programming solvers based on the very efficient interior point methodology are used. Significant gains in efficiency are achieved. A heuristic, semi-adaptive scheme to piecewise linearize the yield surfaces is then developed to further reduce the size of the underlying optimization problems. The results show additional gains in efficiency. Finally, major conclusions are summarized, and various aspects suitable for further research are highlighted.
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Li, Ziyun. „Haptic Dissection of Deformable Objects using Extended Finite Element Method“. Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31445.
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Interactive dissection simulation is an important research topic in the virtual reality (VR) community.
There are many efforts on this topic; however, most of them focus on building a realistic simulation system regardless of the cost, and they often require expensive workstations and specialized haptic devices which prevent broader adoption.
We show how to build a realistic dissection simulation at an affordable cost, which opens up applications in elementary education for virtual dissections which are currently not feasible.
In this thesis, we present a fast and robust haptic system for interactive dissection simulations of finite elements based deformable objects which supports two type of haptic interactions: point contacts and cuts.
We design a semi-progressive virtual dissection scheme of deformable objects in a real-time application.
The quality and performance of visual/haptic feedback is demonstrated on a low-end commercial desktop PC with a haptic device.
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Iatridis, Konstantin. „Temperaturoptionen für die Elemente BITO und TORU des FEM-Programms COSA“. [S.l.] : Universität Stuttgart , Zentrale Universitätseinrichtung (RUS, UB etc.), 1996. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB6783421.
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Satof, Mostafa, und Hasanain Hasse Hasson Al-asadi. „Modellering av rörliga laster : Jämförelse av resultat från influenslinje- och influensytametod från FEM-program“. Thesis, KTH, Byggteknik och design, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-255608.
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At present, the usage of FEM-programs becomes wider for loads effect calculation of bridges. Even though the calculation in all FEM-programs works following the same procedure, it differs when it comes to moving loads where we can identify two different approaches, ILM and ISM (influence line and influence surface method). ISM is used in FEM-programs that are most adapted for bridges where moving loads have great influence, while ILM is used in FEM-programs where moving loads are less important as house constructions. The aim is to evaluate the use of ILM programs (eg FEM-Design) when managing of moving loads in bridge and facilities contexts. This is achieved by comparing the results obtained from ILM programs with the results obtained from IYM programs. In addition, it will be checked how FEM-Design envelops the max and min values regarding (most adverse, conditional summation and unconditional summation). The comparison between those two methods was carried out using two different FEM programs based on different methods. Work carried out using FEM-Design (ILM program) and Brigade/Standard (ISM program). A platform bridge has been modeled and analyzed in both programs and a comparison between the results of both models has been performed. This comparison aims to investigate how ILM and ISM works when calculating moving loads and its influence in a bridge plate and in what way these two methods differ. to achieve comparable results between the programs, we examined different parameters and conditions. The thesis has shown which factors influenced the difference av results between FEM-Design and Brigade, and which summation methods that FEM-Design uses.I dagsläget blir användning av FEM-program ännu bredare för lasteffektsberäkning och analys av brokonstruktioner. Trots att beräkningen sker i princip enligt samma process i alla FEM-program skiljer den sig när det handlar om rörliga laster. När det gäller beräkning av rörliga laster identifieras två olika metoder: ILM och IYM (influenslinje- och influensytametod). Influensytametod används i de FEM-program som är anpassade framförallt för brokonstruktioner där rörliga laster har stor påverkan, medan influenslinjemetod används i FEM-program där rörliga laster har mindre betydelse t.ex. huskonstruktioner. Målet är att utvärdera användning av ILM-program (t.ex. FEM-Design) vid hantering av rörliga laster i bro- och anläggningssammanhang. Detta uppnås genom att jämföra resultaten man får från ILM-program med resultaten som fås från IYM-program. Dessutom skall det kontrolleras hur FEM-Design utvärdera max- och minvärdena med hänsyn till mest ogynsamma, vilkorlig summering och ovilkoriga summering. Jämförelsen mellan de två metoderna har utförts med hjälp av två olika FEM-program som är baserade på de olika metoderna: FEM-Design 18 (ILM-program) och Brigade/standard 4.3 (IYM-program). En plattbro (en enkel bro) har modellerats och analyserats i båda programmen och en jämförelse mellan resultaten från båda modellerna har utförts. Denna jämförelse ämnar undersöka hur influenslinje- och influensytametoden fungerar vid beräkning av rörliga laster och dess påverkan i en brobaneplatta, och på vilket sätt dessa två metoder skiljer sig åt. För att uppnå jämförbara resultat mellan programmen undersöktes/studerades olika parametrar och förutsättningar. Examensarbetet har visat vilka faktorer som påverkat skillnaden av resultat mellan FEM-Design och Brigade, och vilka summeringsmetoder som FEM-Design använder.
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Huang, Huai Hui. „Simulação da formação de cavacos usando FEM (Finite Element Method) - temperatura e força“. Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/18/18145/tde-11122007-162007/.
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A distribuição de temperatura, as deformações e as forças na zona de corte durante a formação de cavacos são muito importantes, pois têm grande influência nos resultados dos processos de usinagem como um todo. O desgaste das ferramentas, a precisão das operações de usinagem (dilatação térmica) e o acabamento superficial são alguns desses resultados que afetam a economia do processo. Este trabalho tem o objetivo uma avaliação das potencialidades oferecidas pela simulação da formação de cavacos usando-se FEM (Finite Element Method). Quatros modelos com princípios bastante diferentes são utilizados explorando-se as mais recentes inovações em termos de recursos oferecidos pelo software ABAQUS/Explicit. Nos modelos utilizam-se ferramentas de substrato WC recoberto com TiN usinado aços AISI 4340. As simulações proporcionam o estudo e exame detalhado da distribuição de temperatura, deformações, forças de corte, fluxo de material e uma enorme quantidade de informações que poderão ser muito úteis para a análise de novos processos, otimização de processos existentes, além de abrir novos horizontes no estudo da formação de cavacos. As simulações também demonstram que a complexidade da formação de cavacos cria muitas dificuldades para sua análise usando equações analíticas baseadas em constantes.The distribution of temperature, the deformations and the cutting forces in the cutting zone during chip formation are very important aspects of the process. Therefore they have great influence in results of machining. Tool wear, the precision of the machining operations and the finishing superface are some of these results that affect the economy of the process. This work has the objective of an evaluation offered potentialities for simulating chip formation using FEM (Finite Element Method). Four models with sufficiently different principles are used to exploring the most recent innovations in terms of resources offered by ABAQUS/Explicit software. In the models, WC tools coated TiN was used to machine AISI 4340 steel. The simulations provide a study and detailed examination of temperature distribution, deformations, cutting forces, flow of material and an enormous amount of information that could be useful for the analysis of new processes and optimization of existing processes. Additionally, they open new horizon in the study of the chip formation. The simulations also demonstrate the complexity of the chip formation process, which creates many difficulties for its analysis using based analytical equations in constants. Some comparisons are established with experimental results found in temperature measurements.
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Johansson, Christer. „Numerical Methods for Ports in Closed Waveguides“. Licentiate thesis, KTH, Numerical Analysis and Computer Science, NADA, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1652.
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Waveguides are used to transmit electromagnetic signals.Their geometry is typically long and slender their particularshape can be used in the design of computational methods. Onlyspecial modes are transmitted and eigenvalue and eigenvectoranalysis becomes important.
We develop a .nite-element code for solving theelectromagnetic .eld problem in closed waveguides .lled withvarious materials. By discretizing the cross-section of thewaveguide into a number of triangles, an eigenvalue problem isderived. A general program based on Arnoldis method andARPACK has been written using node and edge elements toapproximate the .eld. A serious problem in the FEM was theoccurrence of spurious solution, that was due to impropermodeling of the null space of the curl operator. Therefore edgeelements has been chosen to remove non physical spurioussolutions that arises.
Numerical examples are given for homogeneous andinhomogeneous waveguides, in the homogeneous case the resultsare compared to analytical solutions and the right order ofconvergence is achieved. For the more complicated inhomogeneouswaveguides with and without striplines, comparison has beendone with results found in literature together with gridconvergence studies.
The code has been implemented to be used in an industrialenvironment, together with full 3-D time and frequency domainsolvers. The2-D simulations has been used as input for full3-D time domain simulations, and the results have been comparedto what an analytical input would give.
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Andrš, David. „Adaptive hp-FEM for elliptic problems in 3D on irregular meshes“. To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Larsson, Louise. „Motorväg till det omedvetna? : Fem psykoterapeuters upplevelser av att lära sig arbeta med Intensive Short-Term Dynamic Psychotherapy“. Thesis, Ersta Sköndal högskola, S:t Lukas utbildningsinstitut, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:esh:diva-2439.
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Inledning: Psykoterapeutiskt arbete med bearbetning av omedvetna känslomässiga konflikter innebär ofta terapiprocesser som varar över lång tid och kan bedrivas med skiftande tekniker. Psykodynamiskt inriktade terapeuters arbetssätt speglar deras teoretiska övertygelse och personliga läggning. Många arbetar intuitivt och med ett eklektiskt förhållningssätt. Att arbeta efter en sekventiell, tydligt formgiven metod är ovanligt inom den dynamiska/analytiska traditionen. Syftet med studien är att undersöka fem psykoterapeuters upplevelse av att lära sig arbeta efter en specifik metod med fokus på affekter; Intensive Short-Term Dynamic Psychotherapy. Frågeställningarna fokuserar på terapeuternas upplevelse av att lära sig arbeta med metoden, deras beskrivning av skillnaderna mellan sitt tidigare arbetssätt och det nya samt hur utbildningen påverkat deras syn på vad som är verksamt i psykoterapi. Metod: Fem psykoterapeuter som gått Patricia Coughlin Della Selvas treåriga ISTDPutbildning har intervjuats. Resultaten visar att terapeuterna upplevde ISTDP metoden som mycket komplicerad att lära sig. Att frångå sitt tidigare mer intuitiva, inväntande arbetssätt har varit svårt. Det aktiva arbetet med försvaren och metodens multifokus kräver mycket av både terapeut och patient, men ger enligt terapeuterna utdelning i form av snabbare positiv förändring för patienten. Terapeuterna anser att ISTDP-utbildningen har givit dem färdigheter och trygghet att arbeta på ett mer aktivt sätt som når fram till bortträngda minnen och affekter och blir till hjälp för patienten. Terapeuternas övertygelse om vikten av att affekter genomlevs i terapirummet har förstärkts under utbildningen. De påtalar också metodens skarpa fokus på intrapsykisk konflikt samt tydlig överenskommelse med patienten kring vad man ska arbeta med som verksamma faktorer. Slutsatser: Att lära sig arbeta med ISTDP upplevs som komplicerat och känslomässigt omvälvande. När man väl blivit förtrogen med metoden ger det aktiva, direkta arbetssättet enligt terapeuterna möjlighet att ta sig dit man har för avsikt att komma i patientarbetet, nämligen till genomarbetning av omedvetna minnen och affekter. En alltför inväntande och försiktig terapeutisk hållning upplevs hindrande för den terapeutiska processen.