Three-dimensional study of rolling contact fatigue using crystal plasticity and cohesive zone method

A three-dimensional (3D) finite element model that includes the microstructure of grains and grain boundaries is developed for studying the rolling contact fatigue (RCF) damage caused by a rolling steel wheel on a steel railway. The 3D model uses a crystal plasticity-based micromechanical framework for simulation of stress-strain behavior inside the grains, and cohesive elements with traction-separation law for modeling the intergranular fatigue damages. A combination of moving normal Hertzian load and tangential loads are employed to mimic the rolling contact conditions. The effect of various parameters such as friction coefficient, traction, partial slip contact and wheel load on RCF is studied. The results reveal that RCF cracks initiate slightly below the surface for large wheel loads and low tractions. The cracks migrate toward the surface as the wheel-rail traction increases. For high tractions, the cracks initiate at the rolling surface. Under partial slip contact condition, there is a large change in rail life for small normalized tractions. With a slight increase in the latter, the rail life significantly decreases. For moderate to large tractions, rail life remains relatively unchanged or slightly increases. The results of the study appear to agree with anecdotal observations by the U.S. railroads from revenue service operation.