测定裂纹尖端形状和张开位移的实验研究

本文提出了用焦散线法、伪焦散线法和计算机技术相结合测定裂纹尖端形状和张开位移的方法，推导出张开型裂纹尖端形状方程，为确定原始裂纹尖端的张开位移，提供了一种全新的光学测量方法．     

纤维增强复合材料圆柱型界面裂纹分析

以裂纹面上的位错函数为未知量将圆柱型界面裂纹问题化成一组奇异积分方程的求解问题．应用Ｍｕｓｋｈｅｌｉｓｈｖｉｌｉ的奇异积分方程理论，分析了圆柱型界面裂纹尖端应力场．针对裂纹尖端分别存在和不存在接触区两种情况，确定了裂纹尖端应力场的奇异性．利用数值方法计算了圆柱型界面裂纹尖端接触区尺寸对剪应力强度因子的影响．     

压电薄板板边导电裂纹尖端的力电场分析

采用有限元方法，分析了压电薄板板边不同长度导电裂纹尖端的力电场分布规律，发现导电裂纹尖端的应力场和电场强度存在明显的集中和奇异现象，集中和奇异的程度与裂纹长度有关。而且，在裂纹延长线上分别存在两点，这里的应力和电场对裂纹长度不太敏感，总等于无裂纹时薄板的均匀应力和均匀电场强度；同时，还研究了导电裂纹尖端的应力强度因子和电场强度因子对裂纹长度的依赖关系，发现在线性本构的前提下，导电裂纹尖端的应力强度因子与电场强度因子之间具有近似的线性关系。     

功能梯度压电板条中电绝缘型运动裂纹的电弹性场

基于三维弹性理论和压电理论，对材料系数按指数函数规律分布的功能梯度压电板条中的反平面运动裂纹问题进行了求解。利用Fourier积分变换方法将电绝缘型运动裂纹问题化为对偶积分方程，并进一步归结为易于求解的第二类Fredholm积分方程。通过渐近分析，获得了裂纹尖端应力、应变、电位移和电场的解析解，给出了裂纹尖端场各个变量的角分布函数，并求得了裂纹尖端场的强度因子，分析了压电材料物性梯度参数、几何尺寸及裂纹运动速度对它们的影响。结果表明，对于电绝缘型裂纹，功能梯度压电板条中运动裂纹尖端附近的各个场变量都具有-1／2阶的奇异性；当裂纹运动速度增大时，裂纹扩展的方向会偏离裂纹面。     

T10钢金属模具中裂纹电磁热止裂的实验研究

自主设计了改进型ZL-2超强脉冲电流发生装置，采用它对T10金属模具钢中裂纹进行脉冲放电止裂。放电时裂纹尖端熔化形成堆焊和高压应力区，使裂纹尖端钝化，达到了止裂的目的。由于脉冲放电超快速加热和冷却，在裂纹尖端处实现了冲击淬火，得到了超细化的隐晶马氏体和细粒碳化物等微观组织，同时围绕裂纹尖端形成了白亮层组织，提高了裂纹尖端处的硬度、强韧性和耐磨性，实验结果验证了理论研究和数值模拟的结果，为将电磁热裂纹止裂技术应用到金属模具裂纹止裂中，进行了基础实验工艺的研究工作。     

确定裂纹尖塑性区的神经网络方法

通过构造反向传播神经网络，对裂纹尖端的应力场进行学习，进而实现对裂纹尖端应力场函数的逼近。经过学习的网格具有相当的联想、记忆能力和一定的稳定性，并且可以快速、准确地计算实际情况中带裂纹构件的裂纹尖端应力场，确定裂纹尖端的塑性区。便于分析带裂纹构件裂纹的扩展。     

界面裂纹问题中的权函数方法

本文将Ｐａｒｉｓ等确定均匀材料中裂纹尖端应力强度因子的权函数方法推广应用到界面裂纹问题，给出了界面裂纹尖端附近或无限大体半无限界面裂纹问题的权函数的显式表达式。利用此权函数表达式可以很简便地求解界面裂纹尖端附近一些外来作用引起的应力强度因子，比如任意分布力、相变应变、位错和热等。作为一个算例，本文计算了界面一侧一个刃型位错引起的应力强度因子。     

带有两个共线裂纹载流薄板温度场的复变函数解

采用复变函数方法对带有两个共线穿透裂纹的导电薄板，在瞬间电流作用下的温度场进行了计算。针对带有两个共线裂纹或夹杂的载流薄板形成了边值问题，给出封闭形式的解，得到了电流在裂纹尖端的奇异特征。在形成了点热源的基础上，导出裂纹端附近区域的温度场表达式，为计算裂纹尖端附近应力场打下了基础。     

THE STRESS FIELD AT MODE I CRACK TIP ON STEEL PIPE UNDER AXIAL TENSION

采用弹性断裂力学Westergaard 的方法,分析在轴向拉伸载荷作用下钢管的Ⅰ型裂纹尖端处的应力场. 基于Ⅰ型裂纹钢管应力场的特征,设定尖端处的应力艾雷函数,给出其应力场模型边界条件和应力场的解析函数,并利用裂纹尖端处的切平面研究裂纹尖端局部应力场,建立了钢管裂纹尖端应力场模型. 通过钢管与平板Ⅰ型裂纹应力场模型的对比,结果表明二者明显不同,钢管裂纹尖端处应力峰值影响范围仅与裂纹长度、拉应力相关.     

三维冲击荷载弹塑性弯曲裂纹张开位移

主要研究冲击载荷作用下的三维弹塑性弯曲裂纹尖端的张开位移问题．综合考虑了冲击作用应力,三维塑性区域边界上正应力与剪应力,利用二阶摄动方法计算了三维弹塑性弯曲裂纹尖端的张开位移．用数值解法计算出三维弹塑性弯曲裂纹尖端张开位移,作图分析了三维弹塑性弯曲裂纹尖端张开位移与三维裂纹体几何尺寸之间的变化关系．三维弹塑性弯曲裂纹尖端张开位移随着三维裂纹体厚度的增大而减小,随着三维裂纹体厚度的均匀增大,三维弹塑性弯曲裂纹尖端张开位移尺寸不断减小,减小的幅度越来越小,最终趋于平面应变状态下的弹塑性弯曲裂纹尖端张开位移尺寸．当三维裂纹体几何尺寸相同时,三维弯曲裂纹尖端动态张开位移随外部冲击载荷的不断增大而逐渐增大,三维弯曲裂纹尖端动态张开位移随动荷系数的增大而迅速增大,建立了一个计算三维弹塑性弯曲裂纹尖端动态张开位移的崭新理论模型．     

Integral transform solution of multi-material structure with finite crack perpendicular to the interface

The plane elasticity problem for layered elastic systems containing a finite crack perpendicular to the interface is considered. To derive the singular integral equations. Fourier transform in conjunction with dislocation is used. The singular integral equation is solved with the Lobatto-Chebyshev method commonly applied to such problems. In order to have an idea about the usefulness of the method described, a two-layer structure which contains a cut parallel toh is considered.     

层状介质中的双Griffith交界裂纹的SH波散射(反平面运动)——近场解

本文研究层状介质中的双Griffith交界裂纹的SH波散射。文中采用积分变换法将双裂纹的弹性波散射化为对偶积分方程,进而将其转化为第一类奇异积分方程组,借助于第一类Chebyshev多项式,给出了奇异积分方程组的解答,并得到了双裂纹的动态应力强度因子的计算公式     

Closed-form solution for two collinear mode-III cracks in an orthotropic elastic strip of finite width

The problem of an orthotropic strip containing two collinear cracks normal to the strip boundaries is considered. The Fourier series method is used to reduce the associated boundary value problem to triple series equations, then to a singular integral equation, which can be solved analytically. Under remote uniform antiplane shear loading, the stress field and the crack sliding displacement are determined analytically and stress intensity factors are also given in a closed form.     

ELASTODYNAMIC ANALYSIS OF A FUNCTIONALLY GRADED HALF-PLANE WITH MULTIPLE SUB-SURFACE CRACKS

The stress fields are obtained for a functionally graded half-plane containing a Volterra screw dislocation.The elastic shear modulus of the medium is considered to vary exponentially.The dislocation s...     

任意梯度分布功能梯度涂层平面裂纹分析

提出可以分析任意梯度功能梯度材料的分层模型,并采用该模型研究功能梯度涂层平面裂纹问题.采用Fourier变换和传递矩阵法将该混合边值问题化为奇异积分方程组,通过数值求解获得应力强度因子.考察了分层模型的有效性,以及材料梯度变化形式、结构几何尺寸和材料梯度参数对裂纹应力强度因子的影响,发现结构几何尺寸、材料梯度变化形式、...     

Numerical methods for solving singular integral equations obtained by fracture mechanical analysis of cracked wedge简

The numerical solutions to the singular integral equations obtained by the fracture mechanical analyses of a cracked wedge under three different conditions are considered. The three considered conditions are: (i) a radial crack on a wedge with a non-finite radius under the traction-traction boundary condition, (ii) a radial crack on a wedge with a finite radius under the traction-traction boundary condition, and (iii) a radial crack on a finite radius wedge under the traction-displacement boundary condition. According to the boundary conditions, the extracted singular integral equations have different forms. Numerical methods are used to solve the obtained coupled singular integral equations, where the Gauss-Legendre and the Gauss-Chebyshev polynomials are used to approximate the responses of the singular integral equations. The results are presented in figures and compared with those obtained by the analytical response. The results show that the obtained Gauss-Chebyshev polynomial response is closer to the analytical response.     

Interfacial crack problem in layered soft ferromagnetic materials in uniform magnetic field

The magnetoelastic plane strain problem of an interfacial Griffith crack between two dissimilar soft ferromagnetic elastic materials subjected to a uniform magnetostatic field is considered within the framework of linear magnetoelasticity. By making use of the Fourier integral transform technique, the mixed boundary problem is then reduced to a pair of singular integral equations of the second kind. Solutions of the singular integral equations are obtained numerically by means of a Jacobi polynomial expansion method. Effects of the magnetic field, the combinations of the magnetic properties of materials and the geometric parameters on the magnetoelastic stress intensity factors in the vicinity of crack tip are shown graphically.     

Singular integral equations and boundary element method of cracks in thermally stressed planar solids

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A clamped rectangular plate containing a crack

In this paper the general problem of a rectangular plate clamped along two parallel sides and containing a crack parallel to the clamps is considered. The problem is formulated in terms of a system of singular integral equations and the asymptotic behaviour of the stress state near the corners is investigated. Numerical examples are considered for a clamped plate without a crack and with a centrally located crack, and the stress intensity factors and the stresses along the clamps are calculated.