Residual Stress Effects on Fatigue of Surface Processed Steels

Procedures are presented for analyzing the cyclic stability and influence on fatigue resistance of residual stress patterns arising from mechanical and thermal surface processing treatments such as shot peening and induction hardening. Cyclic properties and behavioral trends developed using smooth, axial specimens of steels simulating the various microstructures found in surface processed componentry are used to develop criteria to predict cyclic stability, the rate of relaxation for prescribed straining levels, the failure initiation point (surface or subsurface), and expected fatigue lifetime. The validity of the approach is verified using experimental data from the literature. Finally, the incorporation of these procedures in modern computer-based fatigue analysis routines, and opportunities for further enhancements, are discussed.