Peridynamic simulationons of RCF crack growth in laser quenched rail material

Abstract

Laser quenching (LQ) is a promising technology which could be applied on rails to improve their anti-wear properties. However, severe rolling contact fatigue (RCF) damages tend to occur on the LQ treated rail materials. The peridynamics (PD) simulation is a novel method, which is good at addressing issues on discontinuous materials. Thus, the present study aims at exploring the growth mechanism of RCF cracks in the LQ treated rail material using the PD simulation. Meanwhile, rolling-sliding contact experiments were conducted to verify the simulation results. The results indicated that the RCF crack initiated closely to the front edge of the quenching region. During one wheel/rail contact cycle, the crack growth mode was dominated by the sliding mode when the wheel was close to the crack, and by the opening mode when the wheel was above the crack. The crack growth process in the LQ treated rail could be divided into four stages: crack initiation in the quenching region; crack propagation in depth; branch cracks generation at the bottom of quenching region and crack growth along the boundary between the quenching and substrate regions; crack growth into the substrate or back to the surface. The crack growth rate was increased significantly with the increase in crack length in the quenching region, then decreased gradually in the boundary and substrate regions.