B5后桥A356铝合金支承座早期断裂失效分析

Failure Analysis on Early Fracture of A356 Aluminium Support for B5 Rear Axle Assemble

针对某B5后桥A356铝合金支承座台架试验早期断裂的问题,采用宏观分析、化学成分分析和扫描电镜断口观察等方法对支承座的断裂原因进行了分析。结果表明:由于该支承座受到意外挤压而造成其在加强筋处表面产生一较小的凹坑,由此形成的应力集中使零件在随后的台架试验中很快在此处萌生裂纹源;同时由于该支承座在裂纹源附近存在大面积的疏松缺陷,使得已形成的裂纹源快速疲劳扩展,直至最后断裂。最后提出了改进的措施。

Early fracture failure reasons of a A356 aluminium support for the B5 rear axle assemble during bench testing were analyzed by macro analysis,chemical compositions analysis and scanning electronic microscope observation.The results show that because the small pit defect caused by the accidental force at the place of the structural bead resulted in the stress concentration,the crack source appeared earlier in this area.At the same time, there was so much loose defect near the crack source that the crack developed quickly in fatigue form until fracture. At last improvement measures were proposed.