共查询到19条相似文献,搜索用时 171 毫秒
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给出了一种利用有限元技术模拟周期性张力载荷作用下孔边角裂纹扩展过程的方法。首先利用一系列点定义裂纹前沿,据此形成包含奇异单元的二维有限元网格,再扩展为三维网格.然后利用有限元法进行应力应变分析,最后使用Paris定律计算局部扩展增量.以此来更新裂纹的形状和尺寸。该方法还能够自动地重复执行扩展仿真。文中还对三个不同半径的四分之一椭圆形边角裂纹扩展过程进行了仿真和分析比较,以此来取得裂纹在扩展过程中的形状变化特征和不同方向上扩展的特征。 相似文献
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《计算机辅助设计与图形学学报》2017,(9)
物理仿真中当仿真对象与样例具有不同拓扑结构时,现有采用Laplace-Beltrami算子在表面网格上构建形状插值空间的基于样例仿真方法,在重建其欧氏空间表示时会有精度和效率损失.为克服上述问题,提出一种高效地利用Laplace-Beltrami形状空间的基于样例的仿真方法.首先,提出基于有限元形函数离散化方法的Laplace-Beltrami算子在体网格上计算特征函数,该特征函数重建后直接获得体网格位移,避免了近似的投影过程;其次在特征函数构成的形状空间中采用简化的线性插值来计算目标形状,提高了仿真效率;最后依据目标形状计算出的样例引导力,在有限元仿真框架下实现基于样例材料的形变体仿真方法.实验结果表明,该方法可以获得与已有方法相似的仿真结果,并具有更高的仿真效率. 相似文献
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提出了一种海底油气管道裂纹漏磁检测的有限元分析方法。首先根据麦克斯韦方程组和三维有限元分析原理建立了数学仿真模型,并将仿真结果与实际检测实验数据进行比较,验证了该方法的可靠性。最后,通过仿真分析得出了裂纹的深度、宽度等几何参数对漏磁信号特征的影响规律,并给出它们的关系曲线。该方法为实际利用漏磁场分布检测海底油气管道裂纹提供了重要的依据。 相似文献
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针对工程结构早期裂纹损伤,提出了利用压电阻抗法检测损伤区域高频局部动力学特性,通过监测局部动力学特性变化实现对早期损伤监测的方法。建立了压电阻抗有限元仿真模型并进行数值分析,结果显示压电导纳信号峰值频率即为结构某阶谐振频率,压电阻抗法能有效检测结构的动力学特性。针对不同大小裂纹的铝梁结构进行压电导纳仿真和试验研究,仿真和试验结果表明:压电材料的导纳峰值频率随着裂纹损伤增大而减小;同样的损伤程度下,高频谐振频率对损伤更为敏感。利用高频谐振频率变化来监测早期裂纹损伤的产生及发展,具有较好的重复性和信噪比,具有重要的应用前景。 相似文献
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描述了任意形状三维区域的非结构四面体网格生成算法,该算法对不含裂纹的区域、含单裂纹或多裂纹的区域都适用。算法首先使用八叉树来确定网格单元大小,然后采用前沿推进技术来生成网格。在前沿推进过程中,采用基于几何形状和基于拓扑结构的两个步骤来保证前沿向前移动过程中发生问题时仍能进行正确执行,并且使用了一种局部网格优化方法来提高网格划分的质量。最后,将算法运用到带有裂纹的复杂实体模型,实验结果表明该算法具有较强的适用性和较高的性能。 相似文献
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Weight and service life are often the two most important considerations in design of structural components. This research
incorporates a novel crack propagation analysis technique into shape optimization framework to support design of 2-D structural
components under mixed-mode fracture for: (1) maximum service life, subject to an upper limit on volume, and (2) minimum weight
subject to specified minimum service life. In both cases, structural performance measures are selected as constraints and
CAD dimensions are employed as shape design variables. Fracture parameters, such as crack growth rate and crack growth direction
are computed using extended finite element method (XFEM) and level set method (LSM). XFEM employs special enrichment functions
to incorporate the discontinuity of structural responses caused by the crack surfaces and crack tip fields into finite element
approximation. The LSM utilizes level set functions to track the crack during the crack propagation analysis. As a result,
this method does not require highly refined mesh around the crack tip nor re-mesh to conform to the geometric shape of the
crack when it propagates, which makes the method extremely attractive for crack propagation analysis. An accurate and efficient
semi-analytical design sensitivity analysis (DSA) method is developed for calculating gradients of fracture parameters. Two
different approaches—a batch-mode, gradient-based, nonlinear algorithm and an interactive what-if analysis—are used for optimization.
An engine connecting rod example is used to demonstrate the feasibility of the proposed method. 相似文献
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《Advances in Engineering Software》2010,41(2):111-119
A numerical method for 2D LEFM crack propagation simulation is presented. This uses a Lepp–Delaunay based mesh refinement algorithm for triangular meshes which allows both the generation of the initial mesh and the local modification of the current mesh as the crack propagates. For any triangle t, Lepp(t) (Longest Edge Propagation Path of t) is a finite, ordered list of increasing longest edge neighbor triangles, that allows to find a pair of triangles over which mesh refinement operations are easily and locally performed. This is particularly useful for fracture mechanics analysis, where high gradients of element size are needed. The crack propagation is simulated by using a finite element model for each crack propagation step, then the mesh near the crack tip is modified to take into account the crack advance. Stress intensify factors are calculated using the displacement extrapolation technique while the crack propagation angle is calculated using the maximum circumferential stress method. Empirical testing shows that the behavior of the method is in complete agreement with experimental results reported in the literature. Good results are obtained in terms of accuracy and mesh element size across the geometry during the process. 相似文献
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In this paper,the problem of modeling crack in 2D viscoelastic media is studied using the extended finite element method.The paper focuses on the definition of enrichment functions suitable for cracks assessment in viscoelastic media and the generalized domain integrals used in the determination of crack tip parameters.The opening mode and mixed mode solutions of crack tip fracture problems in viscoelastic media are also undertaken.The results obtained by the proposed method show good agreement with the ana... 相似文献
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为在迭代图像重建算法中获得更高质量的重建图像,推导出TV(Total Variation)正则化项关于重建图像的Fréchet导数,并给出该导数的有限元表示;利用两个数值实验,分别采用不同的网格尺寸和不同的形函数验证该有限元表示结果.数值实验结果表明:采用相同的k次单纯形元时,随着网格不断加密,计算结果的L1和L2误差均下降;采用相同的网格时,线性单纯形元函数计算结果明显优于分片常数有限元和二次单纯形元计算结果. 相似文献
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The modified spectral overlay finite element method is described for a two-dimensional antiplane viscoplastic problem under quasi-static, isothermal conditions. The essential feature of the spectral overlay method is that high resolution of localized steep gradients can be achieved by overlaying a spectral interpolant on a standard finite element mesh. In order to evaluate this method and compare it with the conventional finite element method, a closed-form solution of a shear localization problem in one dimension has been devised. The results show that this method is very powerful in capturing the shape of the gradient field and its peak value in the localization zone. Solutions for an antiplane crack problem are then given to illustrate the effectiveness of this method. 相似文献
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A comparative finite element technique, using conventional finite elements, is presented for the determination of mode I stress intensity factors in two-dimensional crack problems. Given a crack problem to be solved and an auxiliary crack problem for which the mode I stress intensity factor KI is readily available, it is argued that the ratio of KIs for these two problems can be approximated by the ratio of corresponding crack opening displacements near the crack tips, as obtained from finite element solutions. The geometry and loading of the auxiliary problem need not be related to those of the problem to be solved; however, it is essential that the mesh configurations around the crack tips be identical so that numerical errors inherent to the finite element discretization process be the same for the two problems. The validity of this technique is checked for several two-dimensional problems for cracks in homogeneous material whose solutions are available in the literature. Then, it is verified that the method applies to problems of no-slip cracks at a bimaterial interface, in which the no-slip condition is enforced by including no-slip blocks along the crack faces. Finally, this technique is used to predict the stress intensity factors for a four-point bending specimen with an edge no-slip crack at the bimaterial interface. 相似文献
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A finite element error analysis and mesh adaptation method that can be used for improving analysis accuracy in carrying out shape design of structural components is presented in this paper. The simple error estimator developed by Zienkiewicz is adopted in this study for finite element error analysis, using only post-processing finite element data. The mesh adaptation algorithm implemented in ANSYS is investigated and the difficulties found are discussed. An improved algorithm that utilizes ANSYS POST1 capabilities is proposed and found to be more efficient than the ANSYS algorithm. An example is given to show the efficiency. An interactive mesh adaptation method that utilizes PATRAN meshing and result-displaying capabilities is proposed. This proposed method displays error distribution and stress contour of analysis results using color plots, to help the designer in identifying the critical regions for mesh refinement. Also, it provides guidance for mesh refinement by computing and displaying the desired element size information, based on error estimate and a mesh refinement criterion defined by the designer. This method is more efficient and effective than the semi-automatic algorithm implemented in ANSYS, and is suitable for structural shape design. This method can be applied not only to set-up a finite element mesh of the structure at initial design but to ensure analysis accuracy in the design process. Examples are given to demonstrate feasibility of the proposed method. 相似文献
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H. -Y. Hwang K. K. Choi K. -H. Chang 《Structural and Multidisciplinary Optimization》1997,14(2-3):91-99
Thep-version finite element analysis (FEA) approach is attractive for design sensitivity analysis (DSA) and optimization due to its high accuracy of analysis results, even with coarse mesh; insensitivity to finite element mesh distortion and aspect ratio; and tolerance for large shape design changes during design iterations. A continuum second-order shape DSA formulation is derived and implemented usingp-version FEA. The second-order shape design sensitivity can be used for reliability based analysis and design optimization by incorporating it with the second-order reliability analysis method (SORM). Both the second-order shape DSA formulations with respect to the single and mixed shape design parameters are derived for elastic solids using the material derivative concept. Both the direct differentiation and hybrid methods are presented in this paper. A shape DSA is implemented by using an establishedp-version FEA code, STRESS CHECK. Two numerical examples, a connecting rod and bracket, are presented to demonstrate the feasibility and accuracy of the proposed seond-order shape DSA approach. 相似文献
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《Computer Methods in Applied Mechanics and Engineering》2005,194(30-33):3291-3314
Conventional shape optimization based on the finite element method uses Lagrangian representation in which the finite element mesh moves according to shape change, while modern topology optimization uses Eulerian representation. In this paper, an approach to shape optimization using Eulerian representation such that the mesh distortion problem in the conventional approach can be resolved is proposed. A continuum geometric model is defined on the fixed grid of finite elements. An active set of finite elements that defines the discrete domain is determined using a procedure similar to topology optimization, in which each element has a unique shape density. The shape design parameter that is defined on the geometric model is transformed into the corresponding shape density variation of the boundary elements. Using this transformation, it has been shown that the shape design problem can be treated as a parameter design problem, which is a much easier method than the former. A detailed derivation of how the shape design velocity field can be converted into the shape density variation is presented along with sensitivity calculation. Very efficient sensitivity coefficients are calculated by integrating only those elements that belong to the structural boundary. The accuracy of the sensitivity information is compared with that derived by the finite difference method with excellent agreement. Two design optimization problems are presented to show the feasibility of the proposed design approach. 相似文献