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第五章 剪 切 |
5.1 剪切和挤压的概念
5.1.1 剪切Shear的概念
剪切变形的特点:
1)受力特点 杆件两侧作用有大小相等,方向相反,作用线相距很近的外力。
2)变形特点 两外力作用线间截面发生错动,由矩形变为平行四边形。
5.1.2 挤压的概念
构件发生剪切变形时,往往会受到挤压作用。
挤压 :联接和被联接件接触面相互压紧的现象。
例:铆钉孔被铆钉压成长圆孔 。
挤压:发生在两个构件相互接触的表面。
压缩:发生在一个构件上。
5.2剪切和挤压的实用计算
5.2.1剪切的实用计算
计算剪切面上的内力Shear Stress
实用计算法:假定切力在剪切面上的分布是均匀的。
保证构件在工作时不发生剪切破坏,强度条件为
5.2.2挤压的实用计算
实用计算法:认为挤压应力在挤压面上的分布是均匀的。
挤压面积的计算:
1)当接触面为圆柱面的一部分(螺栓、销钉、铆钉):
2)接触面是平面时,接触面积为挤压面积
保证构件局部不发生挤压塑性变形,强度条件为
挤压强度条件也可以解决强度计算的三类问题。
注意: 当联接件与被联接件的材料不同时,应对挤压强度较低的构件进行强度计算。 |
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