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圆柱形部件内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。文中还对具有不同半径比的椭圆形和具有不规则形状的初始裂纹的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。 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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Abaqus新提出的扩展有限元法(ExtendedFiniteElementMethod,XFEM)在解决裂纹扩展问题时有何优点?如何在Abaqus/CAE中设置?对于裂纹扩展问题,传统的有限元法一般采用预先埋设裂纹路径或网格重新划分的方法,让其沿网格扩展,这对模型网格的要求非常高.XFEM能克服以上弊端,在应力集中或裂纹尖端等高应力区域自动将每个单元剖分为2个单元,在模拟裂纹生长时无须重新剖分网格. 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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基于阵列涡流技术的裂纹特征量研究 总被引:1,自引:0,他引:1
阵列涡流传感器能够实现导电材料的大面积高速扫描。不同走向的裂纹对线圈间互感的影响是不同的,因此,测量线圈间的互感能够获得更多的缺陷信息。利用ANSYS软件对横向和纵向裂纹进行了三维有限元仿真,得到了相应的阵列涡流敏感线圈感应电动势幅值变化曲线。仿真结果表明:通过测量线圈间的互感,可以实现对裂纹长度和方向等特征量的检测。 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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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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This study develops a novel hybrid method that combines the finite element method (FEM) and the scaled boundary finite element method (SBFEM) for crack propagation modelling in brittle and quasi-brittle materials. A very simple yet flexible local remeshing procedure, solely based on the FE mesh, is used to accommodate crack propagation. The crack-tip FE mesh is then replaced by a SBFEM rosette. This enables direct extraction of accurate stress intensity factors (SIFs) from the semi-analytical displacement or stress solutions of the SBFEM, which are then used to evaluate the crack propagation criterion. The fracture process zones are modelled using nonlinear cohesive interface elements that are automatically inserted into the FE mesh as the cracks propagate. Both the FEM’s flexibility in remeshing multiple cracks and the SBFEM’s high accuracy in calculating SIFs are exploited. The efficiency of the hybrid method in calculating SIFs is first demonstrated in two problems with stationary cracks. Nonlinear cohesive crack propagation in three notched concrete beams is then modelled. The results compare well with experimental and numerical results available in the literature. 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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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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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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John Dolbow Nicolas Moës Ted Belytschko 《Computer Methods in Applied Mechanics and Engineering》2001,190(51-52)
A new technique for the finite element modeling of crack growth with frictional contact on the crack faces is presented. The eXtended Finite Element Method (X-FEM) is used to discretize the equations, allowing for the modeling of cracks whose geometry are independent of the finite element mesh. This method greatly facilitates the simulation of a growing crack, as no remeshing of the domain is required. The conditions which describe frictional contact are formulated as a non-smooth constitutive law on the interface formed by the crack faces, and the iterative scheme implemented in the LATIN method [Nonlinear Computational Structural Mechanics, Springer, New York, 1998] is applied to resolve the nonlinear boundary value problem. The essential features of the iterative strategy and the X-FEM are reviewed, and the modifications necessary to integrate the constitutive law on the interface are presented. Several benchmark problems are solved to illustrate the robustness of the method and to examine convergence. The method is then applied to simulate crack growth when there is frictional contact on the crack faces, and the results are compared to both analytical and experimental results. 相似文献
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《Computer Methods in Applied Mechanics and Engineering》2005,194(18-20):1913-1946
This paper presents two new methods for conducting a continuum shape sensitivity analysis of a crack in an isotropic, linear-elastic functionally graded material. These methods involve the material derivative concept from continuum mechanics, domain integral representation of interaction integrals, known as the M-integral, and direct differentiation. Unlike virtual crack extension techniques, no mesh perturbation is needed to calculate the sensitivity of stress–intensity factors. Since the governing variational equation is differentiated prior to the process of discretization, the resulting sensitivity equations are independent of approximate numerical techniques, such as the meshless method, finite element method, boundary element method, or others. Three numerical examples are presented to calculate the first-order derivative of the stress–intensity factors. The results show that first-order sensitivities of stress intensity factors obtained using the proposed method are in excellent agreement with the reference solutions obtained using the finite-difference method for the structural and crack geometries considered in this study. 相似文献
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In this paper, a crack identification approach is presented for detecting crack depth and location in beam-like structures. For this purpose, a new beam element with a single transverse edge crack, in arbitrary position of beam element with any depth, is developed. The crack is not physically modeled within the element, but its effect on the local flexibility of the element is considered by the modification of the element stiffness as a function of crack's depth and position. The development is based on a simplified model, where each crack is substituted by a corresponding linear rotational spring, connecting two adjacent elastic parts. The localized spring may be represented based on linear fracture mechanics theory. The components of the stiffness matrix for the cracked element are derived using the conjugate beam concept and Betti's theorem, and finally represented in closed-form expressions. The proposed beam element is efficiently employed for solving forward problem (i.e., to gain accurate natural frequencies of beam-like structures knowing the cracks’ characteristics). To validate the proposed element, results obtained by new element are compared with two-dimensional (2D) finite element results as well as available experimental measurements. Moreover, by knowing the natural frequencies, an inverse problem is established in which the cracks location and depth are identified. In the inverse approach, an optimization problem based on the new beam element and genetic algorithms (GAs) is solved to search the solution. The proposed approach is verified through various examples on cracked beams with different damage scenarios. It is shown that the present algorithm is able to identify various crack configurations in a cracked beam. 相似文献