Implications of water medium for the evolution of rolling contact fatigue under rail surface defect conditions

With existing rail surface defects, third body mediums play an important role in the evolution of Rolling Contact Fatigue (RCF). This study investigates the effect of water mediums on the evolution process of RCF behavior on defective rails. Conical artificial defects were created using an indentation apparatus and wheel-rail rolling contact tests were conducted on a twin-disc test machine. Results indicate that rolling test preparation procedures can affect the development of RCF behavior of the rail material with surface defect under water condition. The morphology from cross-section views under water condition can be divided into four regions due to various RCF behavior evolution based on relative locations from surface defects. However, in all regions, average crack depths, densities and damage degrees increased first and then decreased with the progress of the tests. Damage in areas with and without pre-existing defects under water and dry conditions were compared and discussed. Results also show that the ratio between the remained defect depth and the RCF crack depth would determine whether the existence of defect influence the RCF behavior on the rail material.