Fatigue crack growth behavior of surface crack in rails

Abstract

Rolling contact fatigue damages on the surface of rail such as head check, squats are one of growing problems. Since rail fracture can cause derailment with loss of life and property, the understanding of rail fracture mechanisms is important for reducing damages on the surface of rail. In this study, a two-dimentsional computational model was used to simulate the fatigue crack growth behavior at the surface of rail. The model considers the moving contact pressure and tangential force. Normal pressure of 1100MPa along with traction ratio in the range of −0.4 to 0.4 were investigated for a varing crack size. It has been revealed that the crack growth rate increases with increasing the crack length and start to decrease after a certain depth. When the traction force is applied, the crack growth rate increases to the depth of a/b=0.3 but is similar over the depth of a/b=0.3 regardless of the magnitude of traction coefficient. However, in case the braking force is applied, the crack growth rate dramatically increases with increasing the crack length.