含随机参数的非线性黏弹性有限元计算

进行了粗粒土与结构接触面单调和循环加载试验，基于宏细观测量结果, 扩展了损伤概念以描述该类接触面在受载过程中的物态演化, 及由于物态演化导致的力学特性从初始状态到最终稳定状态的连续变化过程. 揭示了接触面损伤的细观物理基础主要是接触面内土的颗粒破碎和剪切压密这两种物态演化；指出接触面的剪胀体应变可以划分为可逆性和不可逆性剪胀体应变两部分，其中不可逆性剪胀体应变可作为接触面损伤发展的宏观量度，因此其归一化形式可作为一种损伤因子的定义；提出了建立粗粒土与结构接触面一种损伤本构关系的基本思路.

Nonlinear Stochastic Finite Element Analysis Of Viscoelastic Structures

The large deformation problems of viscoelastic structures with random parameters were investigated. The nonlinear viscoelastic stochastic principle of virtual work based on the Total Lagrangian approach was established in which incremental method was applied to solve the hereditary integrals, local averaging method was adopted to discretize the random field, and perturbation method was employed to consider the randomness of parameters. The uncorrelated transformed random variables were introduced into formulations by correlation matrix decomposition algorithm. Only a few independent random variables were required to represent the major characteristics of stochastic structures. It simplified the formulation and saved the computer cost. The geometrically nonlinear relations as well as randomness between displacement and strain field were investigated. After deriving the stochastic constitutive relations between the second Piola-Kirchhoff stress tensor and Green strain tensor, the nonlinear viscoelastic stochastic finite element formulae were put forward. The Newton-Raphson iterative method was used for the solution of the nonlinear equilibrium equations. The combined influence of viscoelasticity, geometrically nonlinearity and randomness could be investigated using the innovated method. Monte-Carlo simulation was used to verify the accuracy of the proposed methods. As a numerical illustration, the responses of viscoelastic solid rocket motor grain under internal pressure were presented. It is proved by the numerical results that the present method is especially suitable for viscoelastic stochastic structures with large deformation.