k组合变形应力状态理论.pptxVIP

Chapter Five;2 . 应变状态分析;组合 变形;组合 变形;基本要求 ;5. 理解强度准则的概念 ; 了解四种常用强度准则的思想和方法 ; 能正确的应用强度准则判别危险点的安全性 .;;;;Strength of materials at one point ;即使是处于简单应力状态下的点 , 其破坏有时也具有复杂性 :;Results: (1) The strength of materials at one point is relation to its mechanic behaviors. (2) The strength of materials at one point is relation to the stresses of this point, many times relation to the stresses along the slope directions. (3) The strength of materials at one point is relation to some maxium stresses of this point.;(3) 组合变形危险点;(3) 组合变形危险点;问题(Question) :; Acoording to the test the point A perhaps is not in safety .;In order to analysis the strength of a point whose stress state is complex , first we must analysis the stresses of this point , next construct its broken criteria , then we can know the point is safe or not in strength .;1. 应力状态分析;1.1 一点应力状态概念;; 问题: 一点应力状态是一个物理量，怎样描述它 ？;;;;;;(3) 应力状态的分类;;(b) : 第二种分类方法;(b) 第二种规定 ( 材料力学规定 );(b) 第二种规定 ( 材料力学规定 );例: 足球射门中的材料力学问题.;;;;;;;;;;x;;;（b）主方向和主应力的计算方法;;三分钟小练习: ;; 物体某点处的主应力就是过该点的所有微元面上法向应力分量的极值或驻值。应力张量存在着三个实数的主应力。; * 主应力就是应力状态矩阵的特征值，主方向就是特征方向。;;;;;习 题;本节内容结束