[表面强化及损伤机理]硌伤形貌对车轮材料滚动接触疲劳特性的影响

采用重力摆锤在车轮试样表面冲击出不同形貌的硌伤坑，基于改进后的MMS-2A 型微机控制摩擦磨损试验平台，研究了未硌伤车轮以及两种硌伤形貌车轮的滚动接触疲劳特性。结合ABAQUS仿真分析的车轮硌伤后残余应力分布情况，探讨了硌伤坑附近裂纹的萌生及扩展机制。结果表明：与未硌伤车轮相比，车轮硌伤处次表层材料沿踏面垂直方向上出现的残余拉应力有助于促进裂纹的萌生和扩展。相同冲击能下，球形硌伤坑附近裂纹长度和角度均大于道砟形硌伤坑附近裂纹长度和角度。球形硌伤坑边缘次表层裂纹的裂纹面较宽，并沿着45°的扩展角度向内部扩展。

Effects of Defect Morphologies on Rolling Contact Fatigue Characteristics of Wheel Materials

The various defect morphologies were impacted on wheel rollers by pendulum machine. The rolling contact fatigue damage characteristics of the normal and two kinds of defected wheel materials were investigated using an improved MMS-2A rolling-sliding wear testing machine. The residual stress distributions on wheel materials after impacting were simulated by ABAQUS, and the crack initiations and propagating mechanism were discussed. The results indicate that the residual tensile stress vertical to the wheel tread emerges on subsurface materials, contributes to the crack initiation and growth compared with the normal wheels. The length and angle of cracks around ball defects are both larger than that around ballast defects under the same impact energy conditions. Moreover, the crack surfaces of the subsurface cracks at the edge of the around ball defects are wider and extend internally along the 45° expansion angle.