Prediction of surface damage behavior in rolling contacts using torsional fatigue results and surface roughness modeling

Abstract

This paper presents a novel approach to predict the effect of surface roughness on surface damage in rolling contacts. Rolling contact fatigue (RCF) tests were conducted on AISI 4130 case carburized steel specimens at two different roughness levels, Ra=0.3μm and 0.1μm, under boundary lubrication regime. The RCF experiments were performed using a Thrust Bearing Surface Pitting Rig employing a ball-on-flat configuration. Surface damage was assessed at different combinations of contact pressure and fatigue cycles using optical surface profilometry. Subsequently, the surface damage stress-life (S–N) results were generated at both roughness levels. Torsional fatigue experiments were also performed on the same material. The torsional fatigue S–N results were combined with stress concentrations at the RCF test surfaces due to roughness to predict the surface damage S–N results. A dry circular contact model incorporating the surface roughness was developed and utilized to compute the stress concentration at the contact. The S–N results based on the von-Mises stresses were compared for RCF and torsional fatigue. The predicted results corroborated well with the experimental findings. The approach developed in this investigation illustrates the fundamental relationship between RCF and torsional fatigue.