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1.
A finite quasi-prismatic (FQP) element is modified to analyze anisotropic materials. The finite quasi-prismatic element is a three-dimensional finite element which uses conventional interpolating functions in two directions and functions based on Chebyshev polynomials in the third direction. This element is used to solve different anisotropic problems and the results are compared with that of conventional finite elements and analytical solutions. 相似文献
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Poisson方程特征值的四种有限元解及比较 总被引:4,自引:0,他引:4
本文应用双线性元、旋转双线性元、拓广旋转双线性元、Wilson元计算Poisson方程的近似特征值.计算结果验证了[4]中特征值问题的有限元渐进误差展开理论的正确性.最后,我们分析了旋转双线性元的近似解的特殊情况,并预测了Wilson元给出特征值的下界. 相似文献
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Matthias Augustin Alfonso Caiazzo André Fiebach Jürgen Fuhrmann Volker John Alexander Linke Rudolf Umla 《Computer Methods in Applied Mechanics and Engineering》2011,200(47-48):3395-3409
The performance of several numerical schemes for discretizing convection-dominated convection–diffusion equations will be investigated with respect to accuracy and efficiency. Accuracy is considered in measures which are of interest in applications. The study includes an exponentially fitted finite volume scheme, the Streamline-Upwind Petrov–Galerkin (SUPG) finite element method, a spurious oscillations at layers diminishing (SOLD) finite element method, a finite element method with continuous interior penalty (CIP) stabilization, a discontinuous Galerkin (DG) finite element method, and a total variation diminishing finite element method (FEMTVD). A detailed assessment of the schemes based on the Hemker example will be presented. 相似文献
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Solid-shell elements can be seen as a class of typical double-surfaced shell elements with no rational degrees of freedom,
which are more suitable for analyzing double-sided contact problems than conventional shell elements. In this study, a solid-shell
finite element model is implemented into the explicit finite element software ABAQUS/Explicit as a user-defined element, through
which the sheet metal forming processes are simulated. The main feature of this finite element model is that the solid-shell
element formulation is embedded into an explicit finite element procedure, compared to the previous studies on the solid-shell
elements under the implicit finite element framework. To obtain a straightforward element, a complete integration scheme is
adopted. No loss of generality, a twelve-parameter enhance assumed strain method is employed to improve the element’s behavior.
Two benchmarks from the NUMISHEET conference and a U-channel roll-forming process are simulated with this explicit solid-shell
finite element model. The calculated results are comparable with experimental and numerical results presented in the literatures. 相似文献
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Various finite element formulations of large amplitude free vibrations of beams with immovably supported ends are discussed in this paper. Analytical formulation based on the Rayleigh-Ritz method is also presented. Numerical results of the analytical approach are seen to be in good agreement with some of these finite element formulations. Mixed finite element formulations based on two methods are derived to study the large amplitude free vibrations of beams. The mixed finite element methods also show good agreement with the analytical and the above finite element formulations. Various points of view raised from time to time on the applicability of these formulations can now be clarified through these formulations and the numerical results. The weakness of the so-called improved Ritz-type finite element model in predicting the nonlinear frequency ratio is highlighted through various results of the above formulations. As a typical example, a hinged-hinged beam on immovable ends is considered for all the above formulations and the nonlinear frequencies show a good agreement amongst themselves at all amplitude levels. 相似文献
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An analytical method is presented to analyze the effect of thermal deformations of an optical pick-up base on the optical properties of DVD optical system. To measure the amount of thermal deformations of an optical pick-up base, finite element analysis and holographic interferometry were used. First, thermal deformations of an aluminum pick-up base was analyzed in thermal environments using finite element analysis; finite element analysis was carried out without the initial surface stress condition. The measurement of thermal deformations by holographic interferometry was carried out to verify finite element analysis results. However, since the finite element analysis results were deviated from those by experiment, the effect of the initial surface stress condition was considered; finite element analysis was carried out with the initial surface residual stress condition, which was obtained from X-ray diffraction measurement. The finite element analysis results with the initial surface stress condition agreed well with the experimental results by holographic interferometry. Finally, to analyze the effect of thermal deformations of the pick-up base on the optical properties of DVD optical system, the deformation of optical path was analyzed. However, the drastic changes of beam spot, beam intensity profile, modulation transfer function curve and wavefront aberration were not observed. 相似文献
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The basis of mapped finite element methods are reference elements where the components of a local finite element are defined.
The local finite element on an arbitrary mesh cell will be given by a map from the reference mesh cell. This paper describes
some concepts of the implementation of mapped finite element methods. From the definition of mapped finite elements, only
local degrees of freedom are available. These local degrees of freedom have to be assigned to the global degrees of freedom
which define the finite element space. We will present an algorithm which computes this assignment. The second part of the
paper shows examples of algorithms which are implemented with the help of mapped finite elements. In particular, we explain
how the evaluation of integrals and the transfer between arbitrary finite element spaces can be implemented easily and computed
efficiently.
Communicated by: M.S. Espedal, A. Quarteroni, A. Sequeira 相似文献
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The basis of mapped finite element methods are reference elements where the components of a local finite element are defined. The local finite element on an arbitrary mesh cell will be given by a map from the reference mesh cell. This paper describes some concepts of the implementation of mapped finite element methods. From the definition of mapped finite elements, only local degrees of freedom are available. These local degrees of freedom have to be assigned to the global degrees of freedom which define the finite element space. We will present an algorithm which computes this assignment. The second part of the paper shows examples of algorithms which are implemented with the help of mapped finite elements. In particular, we explain how the evaluation of integrals and the transfer between arbitrary finite element spaces can be implemented easily and computed efficiently. 相似文献
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The paper is to introduce a new systematic method that can produce lower bounds for eigenvalues. The main idea is to use nonconforming finite element methods. The conclusion is that if local approximation properties of nonconforming finite element spaces are better than total errors (sums of global approximation errors and consistency errors) of nonconforming finite element methods, corresponding methods will produce lower bounds for eigenvalues. More precisely, under three conditions on continuity and approximation properties of nonconforming finite element spaces we analyze abstract error estimates of approximate eigenvalues and eigenfunctions. Subsequently, we propose one more condition and prove that it is sufficient to guarantee nonconforming finite element methods to produce lower bounds for eigenvalues of symmetric elliptic operators. We show that this condition hold for most low-order nonconforming finite elements in literature. In addition, this condition provides a guidance to modify known nonconforming elements in literature and to propose new nonconforming elements. In fact, we enrich locally the Crouzeix-Raviart element such that the new element satisfies the condition; we also propose a new nonconforming element for second order elliptic operators and prove that it will yield lower bounds for eigenvalues. Finally, we prove the saturation condition for most nonconforming elements. 相似文献
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Anders Logg 《Archives of Computational Methods in Engineering》2007,14(2):93-138
The finite element method can be viewed as a machine that automates the discretization of differential equations, taking as
input a variational problem, a finite element and a mesh, and producing as output a system of discrete equations. However,
the generality of the framework provided by the finite element method is seldom reflected in implementations (realizations),
which are often specialized and can handle only a small set of variational problems and finite elements (but are typically
parametrized over the choice of mesh).
This paper reviews ongoing research in the direction of a complete automation of the finite element method. In particular,
this work discusses algorithms for the efficient and automatic computation of a system of discrete equations from a given
variational problem, finite element and mesh. It is demonstrated that by automatically generating and compiling efficient
low-level code, it is possible to parametrize a finite element code over variational problem and finite element in addition
to the mesh. 相似文献
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In this paper, we will design and analyze a class of new algebraic multigrid methods for algebraic systems arising from the
discretization of second order elliptic boundary value problems by high-order finite element methods. For a given sparse stiffness
matrix from a quadratic or cubic Lagrangian finite element discretization, an algebraic approach is carefully designed to
recover the stiffness matrix associated with the linear finite element disretization on the same underlying (but nevertheless
unknown to the user) finite element grid. With any given classical algebraic multigrid solver for linear finite element stiffness
matrix, a corresponding algebraic multigrid method can then be designed for the quadratic or higher order finite element stiffness
matrix by combining with a standard smoother for the original system. This method is designed under the assumption that the
sparse matrix to be solved is associated with a specific higher order, quadratic for example, finite element discretization
on a finite element grid but the geometric data for the underlying grid is unknown. The resulting new algebraic multigrid
method is shown, by numerical experiments, to be much more efficient than the classical algebraic multigrid method which is
directly applied to the high-order finite element matrix. Some theoretical analysis is also provided for the convergence of
the new method. 相似文献
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J. M. Minguez 《Computers & Structures》1993,47(6):917-925
This work applies finite element analysis very simply to cracked plates. An infinite plate and a finite plate, both with a central crack, are considered to study their elastic behaviour and some fracture mechanics concepts, such as the geometry factor and the fracture toughness. These magnitudes are calculated by means of finite element methods and the results are in very good agreement with the established theory, which proves that the finite element approach is very appropriate. The fracture toughness fraction is defined and calculated for a finite plate to predict its failure. 相似文献
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基于Solid Works Simulation的产品设计有限元分析 总被引:3,自引:0,他引:3
本研究旨在探讨有限元分析方法以及基于SolidWorks Simulation的有限元分析方法在产品设计过程中的实际应用。首先详细分析了基于SotidWorksSimulation的有限元分析方法的具体过程,然后通过实例详细探讨了SolidWorks Simulation的基本功能及其使用方法,包括SimulationXPress应力分析、Simulation结构有限元分析以及Simulation优化分析的应用方法。实例证明,基于Solid Works Simulation的有限元分析方法应用于实践中有助于提高产品设计的质量与效率。 相似文献
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This article presents an overview and recent progress of the extended finite element method X-FEM in the analysis of crack growth modeling. It summarizes the important milestones achieved by the finite element community in the arena of computational fracture mechanics. The methodology of X-FEM, different from that of the classical finite element method, presents a very particular interest since it does not force the discontinuities to be in conformity with the borders. It makes possible the accurate solution of engineering problems in complex domains, which may be practically impossible to solve using the classical finite element method. 相似文献
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电容层析成像技术(ECT)是两相流参数检测领域中的一门新技术,在工业生产中有着广阔的应用前景.通过建立有限元模型,编写有限元仿真程序,进行有限元的计算,对两相流典型流型的敏感场场域进行建模仿真,得到的电容值可以作为图像重构的样本数据. 相似文献
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We consider a general framework for analysing the convergence of multi-grid solvers applied to finite element discretisations
of mixed problems, both of conforming and nonconforming type. As a basic new feature, our approach allows to use different
finite element discretisations on each level of the multi-grid hierarchy. Thus, in our multi-level approach, accurate higher
order finite element discretisations can be combined with fast multi-level solvers based on lower order (nonconforming) finite
element discretisations. This leads to the design of efficient multi-level solvers for higher order finite element discretisations.
Received May 17, 2001; revised February 2, 2002 Published online April 25, 2002 相似文献