干-水态下圆形硌伤对钢轨材料滚动接触疲劳特性影响

采用布氏硬度仪在钢轨试样表面制得不同尺寸的圆形硌伤,利用MMS-2A型微机控制摩擦磨损试验机研究了未硌伤和硌伤钢轨的表面硬度、磨损量及滚动接触疲劳损伤特性.结果表明:与未硌伤钢轨相比,硌伤钢轨的表面硬度和磨损量都有所增加;随硌伤尺寸增加,钢轨磨损量与硬度随之增大.较小尺寸的硌伤坑(1.6 mm)有助于减轻硌伤处疲劳裂纹的产生,硌伤坑超过临界值(2.0 mm)则会加重硌伤区附近疲劳裂纹的萌生并导致支裂纹和垂向裂纹的出现.未硌伤钢轨疲劳裂纹以沿晶扩展为主,大尺寸硌伤钢轨试样的疲劳裂纹呈现穿晶扩展现象.

The Effect of Round Defects on Rolling Contact Fatigue Characteristics of Rail Materials under Dry-wet Conditions

The various sizes of round defects were manufactured on the rail rollers using a Brinell hardness tester. The surface hardness, mass loss and rolling contact fatigue damage characteristics of the normal and defected rails materials were investigated using a MMS-2A rolling-sliding wear testing machine. The results indicate that the surface hardness and mass loss of defected rail both increased compared with the normal rail. Moreover, the hardness and mass loss increased when the size of the defect became larger. Small defect (1.6 mm) was conducive to delay the initiation of crack around the defects. While, large defects (2.0 mm and larger) aggravated the fatigue crack damage, which prompted the appearance of branch cracks and vertical cracks. The transgranular propagation occurred on the rail rollers with large defects. However, the intergranular propagation prevailed for normal rail roller.