周向裂纹管道在含扭转各种组合变形时的极限载荷分析

到目前为止，还没有文献给中向裂纹管道在非对称弯曲及扭转组合变形时的塑性极限载荷计算公式。文中根据净截面垮塌准则用沙堆比拟法分别求出埋藏裂纹、外表面裂纹、内表面裂纹、穿透裂纹管道发生扭转变形时的塑性极限扭矩；给出含周向裂纹薄壁管道横截面上的剪应力分布规律，其塑性极限扭矩等于一个闭口薄壁截面与一个开口薄壁截面圆环的塑性极限扭矩之和，闭口薄壁截面的壁厚为管道壁厚减裂纹深度；开口薄壁截面的壁厚为裂纹的深度。推导了各种周向裂纹管在内压、轴力、扭矩及非对称弯矩共同作用时的塑性极限载荷关系式，并由此给出其他一些组合变形时的极限载荷计算公式。本文结果可供管道安全评价时参考。

PLASTIC LIMIT LOAD ANALYSIS OF CIRCUMFERENTIALLY CRACKED PIPES UNDER THE COMBINED LOADS OF TORQUE, AXIAL FORCE, INTERNAL PRESSURE AND UNSYMMETRICAL BENDING MOMENT

Up to now, no paper has been published on analysis of plastic limit load for circumferentially cracked pipes under unsymmetrical bending moment and torque. In this paper according to Net Section Collapse Criterion, the plastic limit torque formulae are derived for circumferential surface cracks, embedded cracks and through wall cracks in pipes under torsion by using the method of sand heap analogy, and gives the distributive pattern of torsion shear stress on the cracked section of the pipe. The plastic limit torque is equal to the sum of that in a closed and in an opened thin wall sections, the thinness of the closed thin wall section equaling to pipe wall thinness minus crack depth, and the opened one equaling to the crack depth. The plastic limit load formulae are presented for circumferentially cracked pipes under various combined load of axial force, torque, internal pressure and unsymmetrical bending moment. The results are very useful for safety assessment of defect pipes.