THERMOMECHANICAL RELAXATION OF RESIDUAL-STRESS IN SHOT PEENED NICKEL-BASE SUPERALLOY

The thermal and thermomechanical behaviour of the relaxation of the re sidual stresses of a shot peened Astroloy superalloy under tensile cyc lic loads has been evaluated by X-ray diffraction and investigated. Th e stress relaxation under purely thermal conditions (550 and 650 degre es C) and thermomechanical conditions (pulsating tensile loading at 65 0 degrees C) as a function of the exposure time is presented. The pure ly thermal relaxation is interpreted by annihilation and reorganisatio n of the crystalline defects induced by shot peening, whereas the mech anical relaxation is linked to cyclic plasticity of materials. In cons equence, the thermomechanical relaxation is essentially due to the com plex mechanism of the concurrent thermal and mechanical effects. A mod el is used to predict the residual stresses induced by the specified s hot peening conditions and their relaxation under the specified therma l/thermomechanical conditions.