Relaxation of Shot-Peened Residual Stresses Under Creep Loading

Abstract

Shot peening is a commonly used surface treatment process that imparts compressive residual stresses into the surface of metal components. Compressive residual stresses retard initiation and growth of fatigue cracks. During the component loading history, the shot-peened residual stresses may change due to thermal exposure, creep, and cyclic loading. This paper describes a methodical approach for characterizing and modeling residual stress relaxation under elevated temperature loading, near and above the monotonic yield strength of nickel-base superalloy IN100. The model incorporates the dominant creep deformation mechanism, coupling between the creep and plasticity models, and effects of prior plastic strain. The initial room temperature residual stress and plastic strain profiles provide the initial conditions for relaxation predictions using the coupled creep-plasticity model. Model predictions correlate well with experimental results on shot-peened dogbone specimens subject to single cycle and creep loading conditions at elevated temperature. The predictions accurately capture both the shape and magnitude of the retained residual stress profile.