光滑拉伸试件中不同初始形状孔洞长大的有限元模拟

本文对具有不同硬化指数（ｎ＝０．０５，ｎ＝０．１，ｎ＝０．２）的幂硬化材料的光滑拉伸试样的拉伸变形过程进行了有限元模拟，通过有限元计算和经Ｂｒｉｄｇｍａｎ修正分别得到了试样变形过程中心部应力三维度随应变的变化情况；在此基础上运用控制体胞宏观应力三维度的方法，对含不同初始形状孔洞的体胞模型进行了有限元分析，计算结果表明：（１）孔洞初始形状和材料硬化特性对试样的拉伸破坏过程有重要影响；（２）Ｂｒｉｄｇ     

岩石节理粗糙面的分形几何特性与剪切强度关系的实验研究

自然形成的岩石节理面的表面形状具有分形特性，利用分形理论来描述岩石节理的粗糙特性，并确立与岩石节理面的剪切力学特性间的关系对于指导岩体工程设计，和管理具有重要一研究利用开发设计的三维激光测距仪在精确测定岩石节理面的表面形状４ 基础上，依据变量图法建立了 岩石节理面的     

An intermediate model method for obtaining a discrete relaxation spectrum from creep data

A convenient method is described for obtaining a discrete stress relaxation spectrum from linear viscoelastic creep data by means of a three-stage process. In stage one, a discrete retardation spectrum is fitted to the creep data using a least squares procedure, subject to the constraint that the discrete spectrum must be a specified order of polynomial function of the retardation time. In stage two, the resulting generalised Voigt model is solved numerically for an imposed step in strain, to determine the stress relaxation modulus function of time. In stage three, a discrete relaxation spectrum is fitted to the calculated stress relaxation modulus function. Although three stages are involved instead of the usual two, the procedure has been found to have certain practical advantages. These advantages make it suitable for the generation of relaxation spectra needed in viscoelastic stress analyses of solids, for example by the finite element method. In order to illustrate the proposed procedure it is applied to both artificial data and experimental creep data for poly(methyl methacrylate) at 70°C and at the glass transition.     

不同材料交界面上接触应力的有限元分析

工程中有许多不同材料组成的结构。对这类复合结构，正确计算材料交界面上的接触应力是非常重要的。通常的位移有限元法得到的应力是不连续且欠准确的。本文提出了一种新的用于不同材料交界面处的接触单元。应用虚位移原理和结合考虑材料交界面上的约束条件，文章建立了接触单元的刚度矩阵和等效荷载向量。该单元具有算法简单，程序容易实现的优点。计算实例证实了该单元的实用性和可靠性。     

A DEVELOPMENT OF BEM TO TWO DIMENSIONAL ELASTICITY

This paper presents a new boundary integral equatiòn for two-dimensional elasticity with the stress component σ_(ij)t_it_j as one of the boundary values,where t_i is the direction cosine of the tangent on the boundary.This form of BEM hasan advantage in that the stress component σ_(ij)t_it_j on the boundary can be calculateddirectly from the numerical solution.The present formulation for plane problems usestwo kernels,the one is logarithmically singular and the other is 1/r singular.Theeffectiveness of the approach is also discussed through test examples.     

奇性校正特解场法计算任意点应力和位移

本文将边界应力积分方程中的强奇性边界积分化为Ｃａｕｃｈｙ主值积分，证明了该主值积分的存在性，并给出它在变量替换中的比尺附加项显式；运用刚体位移法和单位应力场法将强奇性主子块和应力奇性系数矩阵表为同行副子块的线性组合，再配用极坐标变换和适当的数值求积计算各副子块。本法无论对平面问题还是空间问题，是光滑边界点、侧棱点还是角点，有限域或无限域，受载还是变温，都一概适用，而且可以扩展用来计算近边界点，公式统一，程序通用，数值效果良好。     

Subharmonic transition to turbulence in channel flow

A direct numerical simulation of subharmonic transition to turbulence in channel flow has been performed. The stages of primary and secondary instability have been identified in the results leading to a staggered pattern of A-shaped vortices. The associated staggered symmetry has been found to persist up to rather late stages of the breakdown process. This symmetry rapidly disappears in the final stage of transition and a developed turbulent flow is attained. A pronounced difference in the development between the two channel halves is observed which is consistent with the predictions of secondary instability theory.     

GREEN＇S FUNCTIONS OF TWO－DIMENSIONAL ANISOTROPIC BODY WITH A PARABOLIC BOUNDARY

ＧＲＥＥＮ＇ＳＦＵＮＣＴＩＯＮＳＯＦＴＷＯ－ＤＩＭＥＮＳＩＯＮＡＬＡＮＩＳＯＴＲＯＰＩＣ ＢＯＤＹ ＷＩＴＨ Ａ ＰＡＲＡＢＯＬＩＣ ＢＯＵＮＤＡＲＹ（胡元太）（赵兴华）ＧＲＥＥＮ＇ＳＦＵＮＣＴＩＯＮＳＯＦＴＷＯ－ＤＩＭＥＮＳＩＯＮＡＬＡＮＩＳＯＴＲＯＰ?..     

Dynamic analysis of geometrically nonlinear robot manipulators

In this paper, a method for the dynamic analysis of geometrically nonlinear elastic robot manipulators is presented. Robot arm elasticity is introduced using a finite element method which allows for the gross arm rotations. A shape function which accounts for the combined effects of rotary inertia and shear deformation is employed to describe the arm deformation relative to a selected component reference. Geometric elastic nonlinearities are introduced into the formulation by retaining the quadratic terms in the strain-displacement relationships. This has lead to a new stiffness matrix that depends on the rotary inertia and shear deformation and which has to be iteratively updated during the dynamic simulation. Mechanical joints are introduced into the formulation using a set of nonlinear algebraic constraint equations. A set of independent coordinates is identified over each subinterval and is employed to define the system state equations. In order to exemplify the analysis, a two-armed robot manipulator is solved. In this example, the effect of introducing geometric elastic nonlinearities and inertia nonlinearities on the robot arm kinematics, deformations, joint reaction forces and end-effector trajectory are investigated.     

应用脉冲全息法研究爆炸引起的地表振动

本文介绍了应用于爆炸应力波研究的脉冲激光全息实验方法:记录了三维模型中爆炸应力波引起的表面位移的全息干涉图:经对干涉条纹图的分析和计算.发现小药量爆炸引起的表面振动随药包埋深的增加而减弱。