某铁路钢轨伤损及其形成机理研究

Analysis on typical rail damage of high speed railway

钢轨伤损制约着轮轨接触稳定,影响行车安全。针对某铁路钢轨在线服役中产生的伤损,采用Axio Observer 5m金相显微镜、Empyrean型X射线衍射仪、Sigma 500型扫描电镜、FALCON 500显微硬度计进行多方位检验,基于有限元仿真技术重现了车轮异常启动状况下的钢轨接触部位瞬时温度场分布。分析结果表明:该钢轨伤损属于典型擦伤,伤损深度超过2 mm,钢轨伤损部位随着踏面深度的增加,马氏体含量逐渐减少,残余奥氏体含量逐渐增多,导致其对应的显微硬度值逐渐降低。残余奥氏体被马氏体组织包围,增加微裂纹继续扩展的阻力,钝化裂纹尖端,在轮轨表层剪切应力共同作用下,为微裂纹扩展提供通道,诱导微裂纹横向扩展,最终导致钢轨擦伤区域剥离破坏。计算机仿真结果与实际伤损特征基本吻合。

Rail damage restricts the stable contact between wheel and rail and affects the driving safety.Regarding the damage of a railway rail in on-line service,the multi-directional inspections had been carried out by using Axio observer 5m metallographic microscope,Empyrean X-ray diffractometer,sigma 500 scanning electron microscope and Falcon 500 microhardness tester.Based on the finite element simulation technology,the instantaneous temperature field distribution of the rail contact part under the abnormal starting condition of the wheel was reproduced.The analysis results show that the rail damage is a typical scratch with a damage depth of more than 2 mm.With the increase of tread depth,the volume fraction of martensite gradually decreases and the volume fraction of retained austenite gradually increases,so that the corresponding microhardness value gradually decreases.The retained austenite is surrounded by martensite structure,which increases the resistance to the continuous propagation of microcracks and passivates the crack tip.Under the joint action of wheel rail surface shear stress,it provides a channel for microcrack propagation,induces microcrack transverse propagation,and finally leads to peeling failure in rail scratch area.The computer simulation results are agreement with the actual damage characteristics.