Effect of Residual Stress on Fatigue Strength of Induction-Hardened Steel

Abstract

The effect of residual stress on the fatigue strength of machine members is investigated, with particular reference to an induction-hardened steel. In order to distinguish the effect of residual stress from the effect of changes in microstructure developed by hardening, the fatigue strengths of a solid specimen and a hollow specimen are compared. From the experimental results, the residual stress is found to have effect on the fatigue strength equivalent to that of the mean stress, if the relaxation of the residual stress is taken into account. The mechanism of relaxation of the residual stress under cyclic loadings is also investigated by measuring the stress-strain relation on the surface of an induction-hardened specimen. It is made clear that the relaxation due to plastic deformation in the core can occur, under some conditions determined by the hardness distribution, the residual distribution and the stress distribution due to the applies force.