Effects of residual stress and material gradients produced by induction hardening on rolling contact fatigue

Abstract

This research was conducted to provide a better understanding of the effects of induction hardening on rolling contact fatigue (RCF), using a finite element analysis. The finite element analysis was developed in 3D to estimate the maximum loading and the positions of crack nucleation sites for cylinder rolling contact. Rolling contact, with or without surface compressive residual stress, was studied and compared. The residual stress profile was chosen to simulate the effects of an induction hardening treatment on a 48 HRC tempered AISI 4340 steel component. As this hardening process does not only generate a residual stress gradient in the treated component, but also a hardness gradient (called the over-tempered region), both types of gradients were introduced in the model. Residual stresses in compression were generated in the hard case (about 60 HRC), tensile values were introduced in the over-tempered region, where harnesses as low as 38 HRC were set. In order to estimate the maximum allowable loads in the rotating cylinders to target a life of 10⁶ cycles, a multiaxial Dang Van criterion and a shear stress fatigue limit were used, under positive and negative hydrostatic conditions respectively. With the proposed approach, the induction-hardened component was found to have a significantly higher maximum allowable load than that obtained with a nontreated component and it was observed that the residual tensile stress peak in the over-tempered region could become a limiting factor for rolling contact fatigue life. Several simulations were run with various case depths and tensile residual stress peak intensities in the over-tempered region. The goal was to document their load performance in terms of maximum 10⁶ cycles and the related locations at which cracks would appear. It was found that with the hypotheses set in this study, the case depth at which the rolling contact fatigue behaviour was maximized is around 1.2 mm and the maximum load is 375% higher than with a non-treated part. The results are presented in detail and discussed, and recommendations for further development of the model are made.

Date	27 Aug 2019
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Philippe Bocher (Supervisor)