客车脚踏开关弹簧(以下简称弹簧),是客车制动系统中一个非常关键的部件,工作时,弹簧钢丝轴向反复地受扭应力,应力从最大到最小零应力变化。所测弹簧用于8列车辆中,有3列超过80万公里断裂,其余5列均出现早期断裂。弹簧由国外进口,钢牌号、化学成分、加工工艺、热处理工艺等均保密,给断裂原因 Bus foot switch spring (hereinafter referred to as the spring) is a very critical component in the bus braking system. During operation, the spring steel wire is axially and repeatedly subjected to torsional stress and the stress changes from maximum to minimum zero stress. The measured springs were used in eight vehicles, with three out of more than 800,000 km of faults and the remaining five of them showing early faults. Spring imported from abroad, steel grades, chemical composition, processing technology, heat treatment process are kept confidential, to the cause of the fracture