Analysis on Fracture Reasons of the Capacitor Bracket Bolts of a New Energy Bus

The capacitor bracket bolts of a new energy bus fractured. The fracture reasons of the bolts were analyzed by means of macroscopic observation, mechanical property testing, metallographic examination, chemical composition analysis, and so on. The results show that: the fracture mechanism of the bolts was biaxial bending fatigue fracture; the main reason of the fracture was that the design of the joint between the capacitor bracket and the frame was improper, which caused the loose structure and the bending alternating stress to the bolts; the minor reason was the decarburization on the surface of the screws, which decreased the fatigue strength of the bolts.