汽车变速箱悬置断裂原因分析

Fracture Analysis of Automotive Transmission Suspension

汽车变速箱悬置做Z向冲击试验时支臂断裂,抽取库存件进行冲击试验未再发生断裂。为了分析支臂断裂的原因和机理,对零件进行外观分析、金相组织分析、硬度检测、宏观断口分析、断口SEM分析。结果表明:支臂在压铸过程中产生初始裂纹,在冲击性试验载荷作用下发生过载断裂。通过铸件冷却模流图以及再现性试验可知,铸件冷却过程中,由于保压时间不足,铝液尚未完全凝固、脱模,导致在最后凝固区域产生裂纹。

The arm of an automobile transmission suspension fractured during Z-direction impact test and no fracture occurred to other similar parts.In order to analyze the failure cause and mechanism,appearance analysis,metallographic microstructure analysis,hardness testing,macro fracture analysis and fracture surface SEM analysis were carried out.Through investigation and analysis,it is found that initial crack of the arm formed in the process of die casting and then overload fracture occurred during the impact test.Through analyzing the mold flow and reappearance test,it is found that due to insufficient holding time in the cooling process of castings,the molten aluminum was demolded before it completely solidified,leading to initial crack in the final solidification zone.