Fracture Analysis of Automotive Transmission Suspension

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.