Relaxation of Shot-Peened Residual Stresses In a Nickel-Base Superalloy

Creep tests on shot-peened nickel-base superalloy specimens, subject to applied stresses near yield, have been performed at 650°C on IN100 to characterize the residual stress relaxation behavior.  Retained residual stress depth profiles show that yielding during the initial loading produces the largest change in the residual stress profile.  For sustained loads above yield, a continual relaxation of residual stresses occurs with increasing exposure time.  However, for stresses below yield the retained residual stress profiles are similar to specimens subject to thermal exposure alone.

Baseline virgin samples subject to room temperature plastic deformation and tested under elevated temperature creep conditions display a creep rate dependency on prior plastic strain.  These prestrain experiments simulate the deformation experienced by the material during shot-peening and form the basis of a coupled creep-plasticity constitutive model.  The model successfully predicts the retained residual stress profiles of shot-peened IN100 specimens subject to elevated temperature loading histories.