力学第三章剪切资料.ppt

一、一、剪切的剪切的基本概念和实例基本概念和实例(Basic concepts and examples) (Basic concepts and examples) 1. (Engineering examples) (Engineering examples) (1 1) )螺栓连接螺栓连接(Bolted connections) (Bolted connections) 第三章第三章剪切剪切(Practical calculation for shear and bearing) (Practical calculation for shear and bearing) ( (2 2) )铆钉连接铆钉连接(Riveted connections) (Riveted connections) F F 螺栓螺栓(bolt) (bolt) F F 铆钉铆钉(rivet) (rivet) F F 铆钉铆钉(rivet) (rivet) 第一节第一节剪切的实用计算剪切的实用计算 m轴轴(shaft) (shaft) 键键(key) (key) 齿轮齿轮(gear) (gear) ( (3 3) )键块联接键块联接(Keyed connection) (Keyed connection) ( (4 4) )销轴联接销轴联接(Pinned connection) (Pinned connection) FF A B? d? 1?? nn(合力) (合力) (合力) (合力) FF 2. (Character of external force) (Character of external force) 以铆钉为例以铆钉为例构件受两组大小相等、方向相反、作用构件受两组大小相等、方向相反、作用线相距很近的平行力系作用线相距很近的平行力系作用. .3. (Character of deformation) (Character of deformation) 构件沿两组平行力系的交界面发生相对错动构件沿两组平行力系的交界面发生相对错动. . 4. : : (Three types of failure in connections) (Three types of failure in connections) ( (1 1) )剪切破坏剪切破坏沿铆钉的剪切面剪断沿铆钉的剪切面剪断,如沿,如沿 n n- -n n面剪断面剪断. . ( (2 2) )挤压破坏挤压破坏铆钉与钢板在相互接触面上因挤压而使连接松动,发铆钉与钢板在相互接触面上因挤压而使连接松动,发生破坏生破坏. .( (3 3)拉伸)拉伸破坏破坏钢板在受铆钉孔削弱的截面处, 钢板在受铆钉孔削弱的截面处, 应力增大,易在连接处拉断应力增大,易在连接处拉断. . F F n nn n F F S S剪切面剪切面(shearing plane) (shearing plane) nn(合力) (合力) (合力) (合力) FF 二、二、剪切面剪切面 (area in shear) (area in shear) mm F 剪切面 F S 三三、剪切的应力分析、剪切的应力分析(Analysis of shearing stress) (Analysis of shearing stress) 1. (Calculation of internal force) (Calculation of internal force) F F S S- -剪力剪力(shearing force) (shearing force) FF m m00 S???? FFF xFF? S 2. ( ( Shearing stress Shearing stress ) )A F S??式中, 式中, F F S S - -剪力剪力(shearing force) (shearing force) A A- -剪切面的面积剪切面的面积 (area in shear) (area in shear) 四四. .强度条件强度条件(Strength condition) (Strength condition) [ [??] ] 为材料的许用切应力为材料的许用切应力(Allowable shearing (Allowable shearing stress of a material) stress of a material) (factor of safety) (factor of safety) mm F 剪切面 FF m m????