通过宏观检验、化学成分分析、断口分析以及金相检验,对客车直拉杆断裂的原因进行了分析。结果表明:直拉杆的146°弯处在使用前存在微裂纹,在客车行驶过程中该直拉杆受交变应力的作用,微裂纹以疲劳的方式扩展,当扩展到一定程度,剩余截面不能承受外力作用时发生断裂。

The fracture reason of tension rod of passenger car was analyzed by means of macroscopic examination, chemical composition analysis, fracture analysis and metallographi cexamination. The results showed that microcracks existed at 146° bend of the rod before use, and in the process of the passenger car running, the microcracks expanded by the way of fatigue under alternative stress, finally it fractured when the remaining section could not bear external force.