Degenerate scale problem in antiplane elasticity or Laplace equation for contour shapes of triangles or quadrilaterals

This paper provides several solutions to the degenerate scale for the shapes of triangles or quadrilaterals in an exterior boundary value problem (BVP) of the antiplane elasticity or the Laplace equation. The Schwarz-Christoffel mapping is used throughout. It is found that a complex potential with a simple form in the mapping plane satisfies the vanishing displacement condition (or w = 0) along the boundary of the unit circle when the dimension R reaches its critical value 1. This means that the degenerate size in the physical plane is also achieved. The degenerate scales can be evaluated from the particular integrals depending on certain parameters in the mapping function. The numerical results of degenerate sizes for the shapes of triangles or quadrilaterals are provided.     

Bending of uniformly cantilever rectangular plates

An exact solution is given for the bending of uniformly loaded rectangular cantilever plates by using the idea of generalized simply supported edge together with the method of superposition. As illustrative examples, a square plate and a rectangular plate with the ratio of the clamped edge to the neighbouring free edge equal to two are solved numerically. The results are compared with those obtained from approximate methods to confirm the validity of the method presented.     

反平面剪切裂纹和刚性线问题和带裂纹圆轴扭转问题中的新型积分方程

如果把通常裂纹问题中奇异积分方程中的右端项由应力改为合力,此时积分方程的核也要由奇异核改为对数型奇异核。文中对于反乎面剪切裂纹和刚性线问题和带裂纹圆轴扭转问题,推导出了这种带对数核的积分方程。     

BASIC SOLUTION FOR THE THREE-PHASE COMPOSITE CONSTITUTIVE MODEL IN ANTIPLANE PIEZOELECTRICITY

A basic solution in series form for the three-phase composite cyclindrical model in antiplane piezoelectricity subjected to the action of a singularity in the intermediate matrix region is presented. The solution is obtained through the complex potential approach in conjuction with the techniques of analytical continuation, singularity analysis, Laurent series expansion in an annular region and Cauchy integral formulae, etc. Based on the complex potentials obtained, explicit expressions for the distribution of stress and electric displacement in the three regions are also derived.     

各向异性弹性力学一般边值问题的广义Stroh公式

当边值问题是简单的,即是应力边值问题时,Stroh公式是很有效的。对于混合边值问题,倒如滑动边界条件,Stroh公式中的简洁的矩阵表达式就失效了。我们提出了一个广义的Stroh公式,它可应用于一大类一般的边界条件。简单的边界条件和滑动边界条件是这一类一般边界条件的特殊情形。值得指出的是,这个关于Stroh公式所作的修正并不大。广义的公式和最后的解答看起来很类似于未修正的原公式和原来的解。然而这个修正却可应用于相当广的边界条件。     

反平面压电中三相复合本构模型的基本解

给出了三相圆柱压电复合本构模型在承受奇点作用时的基本解答.该解答是通过复势技术结合解析开拓、奇点分析、圆环域上的Laurent级数展开及Cauchy积分公式的运用等而获得的.在所获得的复势的基础上,文中得到了在基体上的奇点作用时各区域上的应力及电位移分布的表达式.     

弹性力学的一种正交关系

在弹性力学求解新体系中，将对偶向量进行重新排序后，提出了一种新的对偶微分矩阵，对于有一个方向正交的各向异性材料的三维弹性力学问题发现了一种新的正交关系．将材料的正交方向取为z轴，证明了这种正交关系的成立．对于z方向材料正交的各向异性弹性力学问题，新的正交关系包含弹性力学求解新体系提出的正交关系。     

线性非局部弹性理论的修正

本文通过考虑局部化残余力的影响对线性非局部弹性理论进行了修正，由修正后的理论所导出的应力边界条件包含了物体微观结构的长程力的作用，这个结果不仅解释了在裂纹混合边界值问题中线性非局部弹性理论方程的解在常应力边界条件下不存在的问题，而且可以自然地得到裂纹尖端的Ｂａｒｅｎｂｌａｔｔ分子内聚力模型。     

复变量移动最小二乘法及其应用

提出了复变量移动最小二乘法，并详细讨论了基于正交基函数的复变量移动最小二乘 法. 然后，将复变量移动最小二乘法和弹性力学的边界无单元法结合，提出了弹性力学的复 变量边界无单元法，推导了相应的公式，并给出了数值算例. 基于正交基函数的复变量移动 最小二乘法的优点是不形成病态方程组、精度高，所形成的无网格方法计算量小. 复变量边 界无单元法是边界积分方程的无网格方法的直接列式法，容易引入边界条件，且具有更高的 精度.     

MESHLESS METHOD OF DUAL RECIPROCITY HYBRID RADIAL BOUNDARY NODE METHOD FOR ELASTICITY

Combining the radial point interpolation method （RPIM）, the dual reciprocity method （DRM） and the hybrid boundary node method （HBNM）, a dual reciprocity hybrid radial boundary node method （DHRBNM） is proposed for linear elasticity. Compared to DHBNM, RPIM is exploited to replace the moving least square （MLS） in DHRBNM, and it gets rid of the deficiency of MLS approximation, in which shape functions lack the delta function property, the boundary condition can not be applied easily and directly and it＇s computational expense is high. Besides, different approximate functions are discussed in DRM to get the interpolation property, in which the accuracy and efficiency for different basis functions are compared. Then RPIM is also applied in DRM to replace the conical function interpolation, which can greatly improve the accuracy of the present method. To demonstrate the effectiveness of the present method, DHBNM is applied for comparison, and some numerical examples of 2-D elasticity problems show that the present method is much more effective than DHBNM.     

功能梯度条共线Griffith裂纹反平面剪切冲击

研究正交各向异性功能梯度条中多个共线Griffith裂纹的反平面剪切冲击问题．材料两个方向的剪切模量假定按比例同时以特定的梯度变化．采用Laplace和Fourier变换及引进位错密度函数将问题化为求解Cauchy奇异积方程，进而化为代数方程数值求解．考查材料非均匀性、正交性和功能梯度条高度对裂尖动态断裂特性的影响．动应力强度因子的数值结果显示：增加剪切模量的梯度和(或)增加垂直于裂纹面方向的剪切模量，可以抑制动应力强度因子的幅度；若功能梯度条较薄，增大条形域的高度也可抑制裂纹扩展．     

弹性力学的重构核粒子边界无单元法与有限元的耦合法

将重构核粒子边界无单元法(RKP-BEFM)与有限元法(FEM)耦合,形成求解具有区域特征的弹性力学问题的重构核粒子边界无单元与有限元的耦合方法RKP-BEF/FE.推导了重构核粒子边界无单元与有限元耦合方法的离散化公式,建立了节点未知量的耦合方程.重构核粒子边界无单元法和有限单元法的较高精度保证了这一直接耦合方法的成功实现与求解精度.最后给出了平面问题的数值算例,验证了提出的耦合方法RKP-BEF/FE的有效性.     

弹性力学广义平面应力的精化理论

从Papkovich-Neuber通解出发,导出了弹性力学广义平面应力问题的精化理论控制方程.若取零阶近似表示,方程即为通常弹性力学平面应力问题的平衡方程.对略去h2及以上高阶项的八阶方程给出了通解.     

弹性力学应力状态理论求解器开发及应用研究

论文基于吴家龙教授编著的《弹性力学》教材内容和课程"三难"特点,以应力状态理论部分常见题型求解任意微分斜面应力矢量、正应力、切应力、主应力和应力主方向及最大切应力为例,应用Matlab-GUI模块编制应力状态理论求解器,通过界面物理参数输入和结果显示过程,再现弹性力学求解思维,验证学生数理求解结论;把繁琐抽象的力学公式...     

复合材料尖劈和接头端部奇性场的反平面问题研究

提出了一个基于位移的分析尖劈端部奇性位移场和应力场反平面问题的非协调元特征法.该方法与过去原有求解裂纹尖端近似场的有限元特征法有几点不同:(1)导出虚功原理的出发点为二维扇区的散度原理;(2)有限元的单元形式为非协调元;(3)尖劈端部邻域内的位移场假定没有采用奇异变换技术.运用该方法给出了求解正交各向异性复合材料尖劈端部附近奇性应力指数、奇性位移和应力角分布函数的算例.计算结果表明,该方法较原来的有限元特征法所用的单元少而且精度高.     

球面各向同性弹性力学的位移解法

本文引入三个位移函数（ｗ，Ｇ，ψ），将球面各向同性弹性力学运动方程，简化为关于ψ的二阶偏微分方程，和关于Ｗ和Ｇ的联立方程。在静力学问题中，联立方程可进一步简化，ｗ和Ｇ可用另一位移函数Ｆ表示，而Ｆ满足一个四阶偏微分方程。在球壳固有振动问题中，则简化为一个独立的二阶常微分方程，和另两个二阶的联立的常微分方程，证明了在多层球壳中，它们分别对应独立的两类振动。改进了常微分方程的解法，并计算了一个二层球壳的频率。     

Hamilton体系下弹性力学的两个守恒律

采用与前稍有不同的方法,将Ｈａｍｉｌｔｏｎ体系引入弹性力学中,并讨论了相应的Ｈａｍｉｌｔｏ函数的守恒性和动量守恒定律,从而丰富了弹性力学的Ｈａｍｉｌｔｏｎ求解体系。     

弹性与断裂力学复变方法研究进展——纪念弹性与断裂力学复变函数法提出100周年

1909年,俄国数学力学家哥洛索夫首先将复变函数方法应用于二维弹性力学问题,揭开了弹性力学复变方法研究的序幕.100年来,复变方法在求解弹性与断裂力学问题中取得了很大发展,特别在断裂力学中的应用尤为成功.2009年恰逢弹性力学复变方法提出100周年,该文试图总结100年来复变方法在经典断裂力学、复合材料断裂力学、新型材料断裂力学以及三维空间断裂问题中的发展与应用,以作纪念.     

EXACT SOLUTION FOR ORTHOTROPIC MATERIALS WEAKENED BY DOUBLY PERIODIC CRACKS OF UNEQUAL SIZE UNDER ANTIPLANE SHEAR

Orthotropic materials weakened by a doubly periodic array of cracks under far-field antiplane shear are investigated, where the fundamental cell contains four cracks of unequal size. By applying the mapping technique, the elliptical function theory and the theory of analytical function boundary value problems, a closed form solution of the whole-field stress is obtained. The exact formulae for the stress intensity factor at the crack tip and the effective antiplane shear modulus of the cracked orthotropic material are derived. A comparison with the finite element method shows the efficiency and accuracy of the present method. Several illustrative examples are provided, and an interesting phenomenon is observed, that is, the stress intensity factor and the dimensionless effective modulus are independent of the material property for a doubly periodic cracked isotropic material, but depend strongly on the material property for the doubly periodic cracked orthotropic material. Such a phenomenon for antiplane problems is similar to that for in-plane problems. The present solution can provide benchmark results for other numerical and approximate methods.     

GREEN''''S FUNCTIONS FOR 2D PROBLEMS OF ANISOTROPIC PIEZOELECTRIC MATERIAL WITH A STRIP REGION

By using Stroh's formalism and the conformal mapping technique, we derive the simple explicit elastic fields of a generalized line dislocation and a generalized line force in a general anisotropic piezoelectric strip with fixed surfaces, which are two fixed conductor electrodes. The solutions obtained are usually considered as Green's functions which play important roles in the boundary element methods. The Coulomb forces of the distributed charges along the region boundaries on the line chargeq atz ⁰ are analysed in detail. The results are valid not only for plane and antiplane problems but also for the coupled problems between inplane and outplane deformations.