应力协调迭代法在高速冲击动力有限元中的应用

在EPIC[2][3],NONSAP[4]等弹塑性撞击动力有限元程序中,有一个共同的弱点是都采取了静力有限元方法,把位移函数用线性插值表示.单元之间应力是非协调的.因此应用虚功原理的基础不合理.为了克服以上困难,本文引入一个新的方法,即协调应力迭代法.实例表明,这种方法在冲击动力有限元计算中是稳定和精确的,同时具有减小单元刚度的作用.     

关于含双参数的非线性常微分方程的奇异摄动*

本文应用微分不等式方法研究含双小参数的非线性常微分方程的边值问题,作出渐近解并对余项进行估计.     

The numerical simulation of turbulent flows of Newtonian and a sort of non-Newtonian fluid in 180-degree square sectioned bend

Using k-εmodel of turbulence and measured wall functions.turbulent flows ofNewtonian(pure water)and a sort of non-Newtonian fluid(dilute,drag-reduction solutionof polymer in a180-degree curved bend were simulated numerically.The calculated resultsagreed well with the measured velocity profiles.On the basis of calculation andmeasurement,appropriateness of turbulence model to complicated flow in which the large-scale vortex exists was analyzed and discussed.     

The effect of transverse shear deformation on stress concentration factors for shallow shells with a small circular hole

Simplified equations are derived for the analysis of stress concentration for shear-deformable shallow shells with a small hole.General solutions of the equations are obtained,in terms of series,for shallow spherical shells and shallow circular cylindrical shells with asmall circular hole.Approximate explicit solutions and numerical results are obtianed forthe stress concentration factors of shallow circular cylindrical shells with a small hole onwhich uniform pressure is acting.     

The improvement of the general expression for the stress function Φ of the two-dimensional problem

In this paper, it is pointed that the general expression for the stress function of the plane problem in polar coordinates is incomplete. The problems of the curved bar with an arbitrary distributive load at the boundries can’t he solved by this stress function. For this reason, we suggest two new stress functions and put them into the general expression. Then, the problems of the curved bar applied with an arbitrary distributive load at r=a,b boundaries can be solved. This is a new stress function including geometric boundary constants.     

The solution of rectangular plates with large deflection by spline functions

In this paper, Von Karman ’s set of nonlinear equations for rectangular plates with large deflection is divided into several sets of linear equations by perturbation method, the dimensionless center deflection being taken as a perturbation parameter. These sets of linear equations are solved by the spline finite-point (SFP) method and by the spline finite element (SFE) method. The solutions for rectangular plates having any length-to-width ratios under a uniformly distributed load and with various boundary conditions are presented, and the analytical formulas for displacements and deflections are given in the paper. The computer programs are worked out by ourselves. Comparison of the results with those in other papers indicates that the results of this paper are satisfactorily better.     

Anisotropy degree of nonlinear solids

This research aims at the generalization of the concept of anisotropy degree of linearly elastic solids which has been defined and investigated in detail by Zhang [1988] to that of nonlinear and non-elastic solids. The properties of the anisotropy degrees defined here show that they are reasonable.     

缓慢调制波在多孔海床上的演化

本文采用多重尺度法分析了具有缓慢调制的波列在多孔海床上的演化问题.海床上部波浪采用了势流理论,海床下部的渗流采用了Darcy定律.两者在海床面上进行衔接,从而导出了上部波浪的波幅一阶和二阶的调制方程,并求出了相应的解,下部渗压场的解亦同时给出.     

四边简支对称正交层合矩形板的非线性弯曲问题

本文在von Kármán型板理论的基础上,采用双重Fourier级数方法,研究了对称正交层合矩形板在简支边条件下,承受任意分布横向载荷和面内载荷联合作用的非线性弯曲问题,得到了满足控制方程和边界条件的解.     

非线性固体的各向导性程度

这篇文章目的在于将在Rychlewski和张进敏(1988)中得到详细研究的线弹性体各向异性度的概念推广到非线性非弹性体.所定义的各向异性度的良好特性说明了其合理性.