基于有限元分析的螺钉断裂失效研究

油泵进行可靠性强化振动试验时发现一个螺钉提前断裂。通过宏微观观察和组织、硬度检测手段,对该螺钉的断裂性质和断裂原因进行了分析。结果表明:螺钉为疲劳断裂,主要是由螺帽与螺孔周围的不良接触导致。为进一步分析不良接触现象对螺钉应力分布的影响,进行了有限元分析,计算结果表明:局部集中力能够明显改变螺钉应力分布状态,显著增加了与局部集中力同侧的螺纹底部的最大应力水平。综合分析后可知,不良接触现象中焊点与螺帽之间的不良接触是螺钉断裂的主要原因。

Fracture Failure Analysis of Screw Based on FEM

One screw of a lubropump fractured during strengthening reliability test. The fracture mode and cause were studied by macro and micro observa-tion, metallographic examination, and hardness measurement. The results show that the failure mode of the screw is fatigue fractur, which was mainly caused by the poor contacted state between the screw cap and the surface near the hole. The effect of the poor contact state on stress distribution was further studied by finite element method (FEM). The computation results shows local loading could change stress distribution of screw and obviously increase the maximum stress of the bottom of thread at the same side with local loading, and it could be concluded that the screw fracture was mainly caused by the weld point con-tacting the cap of screw.