第二章拉伸压缩、剪切.ppt

第二章轴向拉伸和压缩
Mechanics of Materials
Chapter2 Axial Tension pression
材料力学
§2-1 轴向拉压的概念及实例(Concepts and examples of axial tension & compression)
第二章轴向拉伸和压缩
Chapter2 Axial Tension pression
§2-2 内力计算
(Calculation of internal force )
§2-3 应力及强度条件
(Stress and strength condition)
§2-4 材料在拉伸和压缩时的力学性能(Material properties in axial tension pression)
§2-5 拉压杆的变形计算(Calculation of axial deformation)
§2-6 拉压超静定问题
(Statically indeterminate problem of axially loaded members)
§2-7 剪切变形
(Shear deformation)
钢压杆
§2-1 轴向拉压的概念及实例
(Concepts and example problems of axial
tension & compression)
一、工程实例( Engineering examples)
三、变形特点(Character of deformation)
沿轴向伸长或缩短
二、受力特点(Character of external force)
外力的合力作用线与杆的轴线重合
四、计算简图(Simple diagram for calculating )
F
F
F
F
轴向压缩
(pression)
轴向拉伸
(axial tension)
m
m
F
F
一、求内力(Calculating internal force)
设一等直杆在两端轴向拉力 F 的作用下处于平衡,欲求杆件横截面 mm 上的内力.
§2–2 内力计算
( Calculation of internal force )
Method of section · axial force
Calculation of the internal forces is the foundation to analyze the problems of strength、rigidity、stability etc. The general method to determine internal forces is the method of section.
Basic steps of the method of section:
① Cut off:Assume to separate the rod into two distinct parts in the section in which the internal forces are to be determined.
②Substitute:Take arbitrary part and substitute the action of another part on it by the corresponding internal force in the cut-off section.
③Equilibrium:Set up equilibrium equations for the remained part and determine the unknown internal forces according to the external forces acted on it.(Here the internal forces in the cut-off section are the external forces for the remained part)
15
在求内力的截面m-m 处,假想地将杆截为两部分.
取左部分部分作为研究对象。弃去部分对研究对象的作用以截开面上的内力代替,合力为FN .
m
m
F
FN
1、截面法(Method of sections)
截开
m
m
F
F
代替