关键词: 底护板；断裂失效；综合耐久试验；应力分析；涉水工况

Abstract: For the cracking problem of the metal bracket for the underbody guard plate of an electric vehicle, an analysis is conducted on the macro morphology, micro fracture, metallography, and mechanical testing of the cracked samples. It is found that the failure mode of the bracket is typical high-cycle fatigue fracture. The impact force curve under wading conditions is collected and combined with a finite element analysis model to reproduce the stress concentration phenomenon of the original bracket design under this load. An optimized structural solution is proposed by adding reinforcing ribs and flanges. Simulation and bench mechanical test results show that the maximum stress of the optimized bracket is reduced by 12%, and the tear strength is increased by 18%. Finally, the test vehicle equipped with the optimized bracket successfully passed the complete vehicle comprehensive durability test verification without any further cracking, proving the effectiveness and reliability of this optimization solution.

Key words: underbody guard; fracture failure; comprehensive durability test; stress analysis; water wading condition