Failure analysis of engine mounting bracket of a passenger car

This paper presents the failure analysis of an engine mounting bracket. During the proving ground testing, the right brackets of the three testing cars get broken or cracked at the mileage about 7,000 km. In order to determine the causes of the failure, a nonlinear finite element method (FEM) and failure morphology analysis together with mechanical properties, chemical compo-nents and micro-structural analyses of the specimen s material have been performed. The metallographic observation shows the precipitates observed at the inner and outer surfaces, which reduces the strength of inter-granular and then causes the fatigue fracture initiation at the inter-granular. The FEM results show that, the max mises stress is right just at the fillet of bracket, where is the initiation of the crack, and it is a little higher than the yield stress of SAPH400. An optimized structure is proposed, the max tress reduces 20%, and the following tests show the optimized bracket achieving the test mileage more than18,000 km and meets the test requirement.

Automated summary

This paper presents a failure analysis of an engine mounting bracket, identifying the causes of failure through various analytical methods and proposing an optimized structure to improve performance, which is validated by subsequent tests.