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当弹性平板受双侧刚性压头对压时,在压头与平面接触角点附近会产生奇异应力场和K-控制区。与I 型裂纹类似,应力强度因子可作为断裂参量描述应力场的应力集中程度。该文利用经典守恒积分方法研究平板双侧刚性压头对压情况下应力强度因子和触压边界开裂的临界载荷问题,给出边界开裂临界开裂条件,并采用有限元法给出数值算例。 相似文献
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《理化检验(物理分册)》2017,(10)
采用多试样法对D406A超高强度钢进行了准静态断裂韧度KⅠC试验,分析了不同应力强度因子幅预制疲劳裂纹对疲劳预裂纹扩展周期、疲劳预裂纹扩展速率、试样断口形貌以及最终断裂韧度试验结果的影响。结果表明:疲劳预裂纹扩展周期和扩展速率均与应力强度因子幅呈指数变化规律,断口上的疲劳裂纹间距及最终断裂韧度试验结果均随应力强度因子幅的增大而增大,在材料断裂韧度KⅠC的20%~30%选择最大应力强度因子进行KⅠC试验结果较为稳定。 相似文献
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利用裂纹张开能量释放率建立了一个求解方形截面管横向裂纹应力强度因子的一个方法。给出了方形截面管裂纹张开能量释放率的 G*-积分表征,以及和应力强度因子的关系。同时也给出了 G*-积分与载荷、几何参量以及机械性能参数的关系,进而得到方形截面管横向裂纹的应力强度因子。给出的方法不仅适用于一般箱形结构件的裂纹问题,也适用于其它有限边界多边管状结构的三维裂纹问题,过程极为简单。 相似文献
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梯度涂层材料中裂纹问题的非均匀元分析 总被引:4,自引:0,他引:4
本文采用非均匀等参有限元的方法研究了薄膜梯度涂层/均匀基材中的界面裂纹问题,并与双材料界面裂纹情况进行了对比计算。研究表明:在均匀基材上采用梯度涂层,与双材料相比可以有效地降低裂尖场应力强度因子;同时还分析了涂层厚度与梯度参数对界面应力强度因子的影响。结果表明:当薄膜厚度大于或等于裂纹长度时,应力强度因子(KI、KII)对其尺度的变化显得不敏感;对梯度参数的影响而言,当材料性能曲线的幂指数m大于1时,裂尖场的应力强度因子KII相对KI很小且基本不随m变化,因此裂尖场与均匀材料情况类似;当m小于1时,应力强度因子KII随m减小而急剧增大,裂尖场由KI及KII控制,断裂趋于混合型。 相似文献
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探讨了HT有限元应用于Ⅰ、Ⅱ和Ⅲ型复合裂纹的弹性断裂问题。分析了Ⅲ型弹性断裂问题的HT有限元方法及高阶奇异性应力强度因子KΙΙΙ,同时,对Ⅰ和Ⅱ型断裂问题的HT有限元原理及断裂强度因子KΙ和KΙΙ的计算也进行了阐述。特别地,在计算三个强度因子时,引入了一种新的方法——附加试函数法,它主要用于满足裂尖特殊的边界条件,提高了三个奇异应力强度因子的精确性与可靠性。最后,根据HT有限元计算结果,讨论了奇异应力强度因子无量纲化系数K/Kc随裂纹单元特殊T函数项数、细划单元数、单元高斯点数及裂尖不同附加试函数的变化规律;获得了应力强度因子精确度和可靠度,并与其它有限元结果进行了比较,阐述了此方法的优越性。 相似文献
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P. H. Wen M. H. Aliabadi D. P. Rooke 《Engineering Analysis with Boundary Elements》1995,16(4):351-362
Indirect boundary element methods (fictitious load and displacement discontinuity) have been developed for the analysis of three-dimensional elastostatic and elastodynamic fracture mechanics problems. A set of boundary integral equations for fictitious loads and displacement discontinuities have been derived. The stress intensity factors were obtained by the stress equivalent method for static loading. For dynamic loading the problem was studied in Laplace transform space where the numerical calculation procedure, for the stress intensity factor KI(p), is the same: as that for the static problem. The Durbin inversion method for Laplace transforms was used to obtain the stress intensity factors in the time domain KI(t). Results of this analysis are presented for a square bar, with either a rectangular or a circular crack, under static and dynamic loads. 相似文献
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Quadratic isoparametric elements which embody the inverse square root singularity are used in the calculation of stress intensity factors of elastic fracture mechanics. Examples of the plane eight noded isoparametric element show that it has the same singularity as other special crack tip elements, and still includes the constant strain and rigid body motion modes. Application to three-dimensional analysis is also explored. Stress intensity factors are calculated for mechanical and thermal loads for a number of plane strain and three-dimensional problems. 相似文献
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An analytical method for mixed-mode (mode I and mode II) propagation of pressurized fractures in remotely compressed rocks is presented in this paper. Stress intensity factors for such fractured rocks subjected to two-dimensional stress system are formulated approximately. A sequential crack tip propagation algorithm is developed in conjunction with the maximum tensile stress criterion for crack extension. For updating stress intensity factors during crack tip propagation, a dynamic fictitious fracture plane is used. Based on the displacement correlation technique, which is usually used in boundary element/finite element analyses, for computing stress intensity factors in terms of nodal displacements, further simplification in the estimation of crack opening and sliding displacements is suggested. The proposed method is verified comparing results (stress intensity factors, propagation paths and crack opening and sliding displacements) with that obtained from a boundary element based program and available in literatures. Results are found in good agreements for all the verification examples, while the proposed method requires a trivial computing time. 相似文献
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This paper presents a boundary element analysis of elliptical cracks in two joined transversely isotropic solids. The boundary element method is developed by incorporating the fundamental singular solution for a concentrated point load in a transversely isotropic bi-material solid of infinite space into the conventional displacement boundary integral equations. The multi-region method is used to analyze the crack problems. The traction-singular elements are employed to capture the singularity around the crack front. The values of stress intensity factors (SIFs) are obtained by using crack opening displacements. The results of the proposed method compare well with the existing exact solutions for an elliptical crack parallel to the isotropic plane of a transversely isotropic solid of infinite extent. Elliptical cracks perpendicular to the interface of transversely isotropic bi-material solids of either infinite extent or occupying a cubic region are further examined in detail. The crack surfaces are subject to the uniform normal tractions. The stress intensity factor values of the elliptical cracks of the two types are analyzed and compared. Numerical results have shown that the stress intensity factors are strongly affected by the anisotropy and the combination of the two joined solids. 相似文献
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The problems of the interface corners between two dissimilar anisotropic viscoelastic materials are studied in this paper. Through the use of the well-known correspondence principle between linear elasticity and linear viscoelasticity, fracture parameters in the Laplace domain can be obtained from the path-independent H-integral for the corresponding problems of anisotropic linear elastic materials. Further application of the correspondence relations for fracture parameters proposed in our recent study then leads us the solutions of fracture parameters in the time domain. To show the applicability and accuracy of the proposed method, several different kinds of numerical examples are presented such as a centered interface crack, free edges between two dissimilar materials, and the interface corners appeared within the electronic packages. The fracture parameters calculated in this study include the orders of stress singularity and the stress intensity factors of opening mode, shearing mode and tearing mode. The proposed method allows the orders of stress singularity be real or complex, repeated or distinct, and the fracture mode be pure mode or mixed mode. 相似文献
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The use of finite element methods to analyse fracture problems is complicated by the stress field singularity which exists at the crack tip. The two most successful methods of approach would appear to be the so-called energy technique and the singularity function formulation. The necessity for extremely fine meshes in the crack tip region can be overcome by the use of special elements which incorporate the required stress singularity in their formulation. The aim of this paper is to develop various promising singularity function elements and assess their performance in the solution of standard test problems. These elements are based on the eight node parabolic isoparametric element; this being the most popular element in general use. Such crack tip elements may be readily incorporated into a mesh of standard isoparametric elements permitting numerical fracture studies to be undertaken without extensive mesh regeneration or refinement. In particular elements based on the use of distorted shape functions, standard shape functions, analytic solutions, a superposition process and a hybrid technique are considered. Test problems of both single and combined mode fracture are employed in the assessment of each model.It is also demonstrated that the hybrid element is a special case of the boundary integral method, and suggestions are made for possible future development. 相似文献
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《Engineering Analysis with Boundary Elements》2002,26(8):691-705
This paper presents a new boundary element method (BEM) for linear elastic fracture mechanics in three-dimensional multilayered solids. The BEM is based on a generalized Kelvin solution. The generalized Kelvin solution is the fundamental singular solution for a multilayered elastic solid subject to point concentrated body-forces. For solving three-dimensional elastic crack problems in a finite region, a multi-region method is also employed in the present BEM. For crack problems in an infinite space, a large finite body is used to approximate the infinite body. In addition, eight-node traction-singular boundary elements are used in representing the displacements and tractions in the vicinity of a crack front. The incorporation of the generalized Kelvin solution into the boundary integral formulation has the advantages in elimination of the element discretization at the interfaces of different elastic layers. Three numerical examples are presented to illustrate the proposed method for the calculation of stress intensity factors for cracks in layered solids. The results obtained using the proposed method are well compared with the existing results available in the relevant literature. 相似文献
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S. T. Raveendra P. K. Banerjee G. F. Dargush 《International journal for numerical methods in engineering》1993,36(11):1909-1926
The stress intensity factors for cracks in three-dimensional, thermally stressed structures are computed by using the boundary element method. While many boundary and volume-integral-based formulations are available for the treatment of thermoelastic problems in solids, the present analysis is based on a recently developed boundary-only formulation. The accuracy of the solutions in the present work is improved by using special elements at the crack front that accurately model the variation of displacement, temperature fields and singularity of traction, flux fields. 相似文献
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In this paper a two-dimensional hyper-singular boundary element method for elastoplastic fracture mechanics analysis with
large deformation is presented. The proposed approach incorporates displacement and the traction boundary integral equations
as well as finite deformation stress measures, and general crack problems can be solved with single-region formulations. Efficient
regularization techniques are applied to the corresponding singular terms in displacement, displacement derivatives and traction
boundary integral equations, according to the degree of singularity of the kernel functions. Within the numerical implementation
of the hyper-singular boundary element formulation, crack tip and corners are modelled with discontinuous elements. Fracture
measures are evaluated at each load increment, using the J-integral. Several cases studies with different boundary and loading
conditions have been analysed. It has been shown that the new singularity removal technique and the non-linear elastoplastic
formulation lead to accurate solutions. 相似文献