Comparing the Influence of Residual Stresses in Bearing Fatigue Life at Line and Point Contact

Abstract

The targeted insertion of compressive residual stresses can positively influence the fatigue life of rolling element bearings. Adapted manufacturing processes such as hard turning and deep rolling can help optimising the subsurface residual stress state of these machine elements, which also improves the surface quality of the bearings raceway. In this contribution, a numerical calculation method was developed to predict the influence of residual stresses on bearing fatigue life. By means of a finite element analysis, the component stresses due to the rolling contact load can be determined. The resulting shear stresses find input in a bearing fatigue life calculation based on the approach of IOANNIDES, BERGLING and GABELLI. This statistically based method refers a material-dependent stress fatigue limit to a local stress related fatigue criterion, which is influenced by the residual stress condition. On this basis, the influence of residual stresses on two different bearing types is investigated. Line contact is represented by a cylindrical roller bearing and an angular contact ball bearing is chosen to investigate the point contact. For angular contact ball bearings, a rolling motion is superimposed by a drilling movement perpendicular to the contact plane, which is caused by the kinematics of the rolling element. The calculation method is used for bearings made of classic bearing steel and bearings made of two different steels by tailored forming in order to regard the residual stress conditions of different manufacturing types. It can be shown that the influence of residual stresses on bearing fatigue life is higher for bearings with line contact than for bearings with point contact.