A stress based critical-plane approach for study of rolling contact fatigue crack propagaton in planet gears

Abstract

This paper presents a contribution to the study of rolling contact fatigue (RCF) in the specific case of a planet gear containing an integrated bearing. Propagation of micro-cracks starting from the bearing race surface and leading to spalling is a typical damage mode of these components. However, in some specific cases, cracks can bifurcate into the core, leading to the complete failure of the component. Based on experimental observations, discussion on the interactions between spalling and in-core cracks suggests a competition between the two phenomena. In order to understand the main drivers of crack propagation, a stress based critical-plane approach is developed and confronted to crack observations. It enables to highlight that several factors, such as the contact pressure at the roller/race interface, the rim ovalization, and residual stresses due to a thermochemical treatment, play a major role on the crack behavior.