乘用车行李厢盖扭杆失效分析

Failure Analysis of Trunk Lid Torsion Rod of a Passenger Car

为解决某车型软工装交样阶段中行李厢盖扭杆断裂的问题,利用OES光谱仪、扫描电子显微镜、光学显微镜和硬度计等技术手段检测失效扭杆的化学成分、宏观断口形貌、微观组织和金相组织。分析结果表明,扭杆断裂属于早期疲劳断裂失效;失效原因是在扭杆成形过程中,扭杆表面存在较为严重的工装压痕缺陷,形成表面裂纹源,在扭转应力作用下,裂纹扩展,最终发生断裂。

To solve the fracture problem of trunk lid torsion rod(Soft Tooling Sample)of a passenger car,we use OES spectrometer,scanning electronic microscope(SEM),optical microscope(OM)and hardometer to detect and analyze the chemical composition,fracture morphoogy,microstructure,hardness and metallographic structure of failed torsion rod.The results showed that the fracture of torsion rod was due to fatigure failure.And the reason for the rod’s fatigue failure was the defects on the rod’s surface which introduced by the forming tool in the production.The defects on the surface was the starting point of crack,the cracks propagated under the torsion stress,and at last caused the torsion rod’s fatigue fracture.