某车型底盘紧固螺柱零件断裂失效分析

Fracture Failure Analysis of Fastening Stud for Chassis

汽车底盘系统联接方式的失效分析可以为车身底盘开发及其联接方式提供优化建议。用扫描电镜对断裂失效螺柱零件的形貌进行观察,形貌分析结果表明,螺柱的初始表面覆盖了氧化物,断口边缘的螺纹处存在损伤和二次裂纹;断口锈迹清洗后的形貌和能谱观察可见,在断口宏观形貌中存在贝纹线。通过扫描电镜放大形貌进一步发现,在裂纹源处存在二次裂纹和氧化物,在裂纹扩展区发现了疲劳辉纹的痕迹。综上,底盘紧固件螺纹的断裂失效原因是疲劳断裂。对螺柱的成分、金相和硬度检测进行分析可知,螺柱件的w(C)=0.385%,金相组织为回火索氏体,洛氏硬度为42HRC,符合螺柱材料使用标准要求。

The fracture analysis could give adivice to the development of chassis and optimizaiton of connection mode.The morphology of stud pieces is observed by using scanning electron microscopy on fracture.The results show that the initial surface of the stud parts is covered with the oxide,and the damage and twice crack fracture exist at the edge of the screw.The fracture morphology of rust after cleaning and energy spectrum observation show that the Bay ridges are found in the fracture morphology in amplification.By scanning electron microscope morphology,it is further found that secondary cracks and oxide exist in the crack source.The fatigue striation marks are found in the crack propagation zone.The analyzed results show that the fracture of the chassis fastener thread failure is fatigue fracture.At the same time,the composition,metallographic examination and hardness analysis of the stud show that the carbon content of the stud is 0.385%,the metallographic structure is tempered bainite and the Rockwell hardness is 42 HRC.