Effects of varying normal loads on the rail rolling contact fatigue behavior under various frequencies and creepages

Track irregularities caused by wheel and rail damage would lead to vibration at wheel-rail contact interfaces, resulting in the fluctuation of normal forces which would further increase the damage to both wheels and rails under operational freight train services. This study aims to investigate effects of varying normal loads on the rolling contact fatigue (RCF) behavior of rails under various creepages and vibration frequencies using a twin-disc test machine. Results indicated that tangential forces and wear rates both increased with the increase in creepages, while they decreased with the increase in vibration frequencies. In addition, surface and subsurface damage parameters, and characteristics of cracks in the railhead including average lengths, depths and angles first increased and then decreased with the increase in creepages, and they all decreased with the increase in vibration frequencies. Further, the sizes of wear debris particles decreased with the increase in both creepages and frequencies.