Relaxation of residual stresses in surface-hardened rotating prismatic elements of structures under creep conditions

A method for solving boundary problems of relaxation of residual stresses in a rotating surface-hardened prismatic specimen under high-temperature creep conditions has been developed. The problem models the stress-strain state of a surface-hardened prismatic rod with one end fixed to an infinitely rigid disk rotating at a constant angular velocity. In the first stage, we solve the problem of reconstructing fields of residual stresses and plastic deformations after the hardening procedure, which play the role of the initial stress-strain state, is solved. In the second stage, we address the problem of relaxation of residual stresses under creep conditions is addressed. A detailed study of the influence of angular velocity on the intensity of residual stress relaxation in different sections along the axial coordinate is carried out for a 10${\times}$10${\times}$150 mm prismatic specimen made of EP742 alloy at a temperature of 650 $^\circ$C, following ultrasonic mechanical hardening of one of its faces. The analysis of the calculation results revealed that for angular velocities ranging from 1500 rpm to 2500 rpm, a non-trivial effect is observed. The relaxation of residual stresses in more stressed sections experiencing axial tensile stresses due to rotation occurs less intensively than in the “tail” section, where the axial load is zero. The obtained results from this study can be useful in assessing the effectiveness of surface-hardened rotating components under high-temperature creep conditions.