列车车钩尾销孔裂纹分析

某型列车运载量增大后，列车车钩尾销孔牵引弧面位置大量出现裂纹。本文车钩尾销孔的化学成分和机械性能进行了检测，观察了车钩钩尾销孔裂纹的宏微观形貌，并对裂纹位置的金相组织进行了检测。结果表明，车钩钩尾销孔裂纹在径向上为脆性断裂特征，而周向上为疲劳断裂特征。分析认为，由于列车运载量增大，车钩尾销孔位置的工作应力增大，同时由于车钩尾销孔处淬硬层与基体的性能差异较大且无明显的过渡层，在工作应力作用下淬硬层首先发生脆性断裂并沿径向扩展，至淬硬层与基体界面处则沿着性能较弱的界面疲劳扩展。

Analysis on Cracks of a Coupler Tail Pinhole of a Train

Cracks were often found near the coupler tail pinhole of the trains with the increase of load. Chemical analysis, mechanical property testing, crack observation, and microstructure examination were carried out to investigate the cause for the cracks. The results show that the radial crack mode is brittle crack but the circumferential crack is fatigue crack. With the increase of the load, there was greater working stress at the contact position of the hole with the pin. Because the performance of the quenching layer is different from that of the matrix and there was no obvious transition layer between the quenching layer and the matrix, brittle fracture first occurred in the quenching layer and then propagated in the radial direction. After the cracks extended to the interface between the quenching layer and the matrix, the cracks extended along the interface with poorer performance in a fatigue way.