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.