Stability of shot peen residual stresses in IN100 subjected to creep and fatigue loading

Abstract

Shot peening is commonly used to retard initiation and growth of fatigue cracks in fracture critical components. During service, the shot-peened residual stresses may change due to thermal-mechanical loading. This paper describes an approach for characterizing and modeling residual stress relaxation in supersolvus IN100 at 650 °C. The model incorporates the dominant creep deformation mechanism, coupling between the creep and plasticity models, and effects of prior plastic strain. Significant shot peen residual stresses are retained even after 300 hours of thermal exposure to 650 °C. Fatigue loading resulted in relaxation only in the initial load-unload cycle for the entire stress distribution. Under uniform applied stresses, residual stress reversal occurred for stresses greater than 1000 MPa. In geometries with steep gradients, such as notches, significant compressive residual stresses are retained near the surface even when the local stresses exceed the yield stress.