新能源客车电容支架安装螺栓的断裂原因分析

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

某新能源客车上的电容支架固定螺栓发生批量断裂。通过对断裂螺栓进行宏观观察、力学性能测试、金相检验、化学成分分析等,分析了其断裂原因。结果表明:螺栓的断裂为双向弯曲疲劳断裂;发生断裂的主要原因是电容支架与车架连接结构设计不当,导致结构松动,使螺栓受到弯曲交变应力作用;次要原因是螺纹表面脱碳,降低了螺栓的疲劳强度。

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.