The Effects of Indent Residual Stresses on Mixed Mode Cyclic Crack Growth Driving Forces for Bearing Inner Rings

The residual stresses produced by plastic dents in a solid cylinder have been evaluated for overload, peak-contact-pressure-to-shear-strength ratios of p_oi/k = 3.5, and p_oi/k = 4. The effects of 2 sets of indent residual stresses on the cyclic crack growth driving forces generated by rolling contact at relative peak pressures of p_or/k = 0.5, 1.0 and 2.0, have been evaluated for 3 conditions. These are: (1) the slowly revolving ring, (2) the rapidly revolving ring with associated press fit and centrifugal stresses, and (3) the rapidly revolving ring with the superimposed circumferential compressive stresses arising from a carburized surface layer. The values of ΔK_I ΔK_II, and the combined mode, ΔK_e, are calculated for 18 different rolling conditions, for small cracks with 8 different inclinations, 5 crack-face friction coefficients, and 21 locations in the dent region. The results show that the ΔK-values for a 2a=20μm long crack can exceed the Mode I threshold when the rim rotates slowly. Larger ΔK-values are obtained in the presence of press-fit and centrifugal stresses. However, the residual stresses of the carburized surface layer more than compensate for the press-fit and centrifugal stresses, reducing the ΔK-values below the levels obtained for the slowly rotating rim.