Experimental and analytical investigation of effects of refurbishing on rolling contact fatigue

Abstract

In this study, the effects of refurbishing on rolling contact fatigue (RCF) in case carburized AISI 8620 steel were experimentally and analytically investigated. A thrust bearing test apparatus (TBTA) was designed and developed to simulate RCF. Initial RCF tests were conducted on AISI 8620 steel specimens to determine the baseline for pristine. Then new specimens were exposed to fatigue cycles equal to 90% of the L10 life of the pristine material. These specimens were then refurbished to the depths of 0.13b and 1.27b (b is the half width of Hertzian contact). The refurbished specimens were then subjected to RCF cycles in the TBTA until a spall appeared on the surface. The experimental results of refurbished specimens indicated a significant amount of fatigue life after refurbishing for both grinding depths. Moreover, it was observed that the remaining useful life of the refurbished test specimens was extended by increasing the depth of the regrinding.For the analytical investigation, a two-dimensional elastic-plastic finite element model was developed to estimate RCF life for pristine and refurbished specimens of case carburized steel. The characteristics of case carburized materials (e.g., variations in hardness and residual stresses) were incorporated in the 2D finite element model. In the present study, a continuum damage mechanics approach was employed to determine fatigue damage accumulation in original and refurbished domains. The results obtained from the experimental and FEA models for pristine and refurbished case carburized steel are in good agreement for both grinding depths.