Relaxation of residual stresses in a surface-hardened rotating cylinder under creep conditions
A technique for calculating the relaxation of residual stresses in a cantilevered rotating cylinder after the procedure of surface plastic deformation under creep conditions has been developed, taking into account the effect of a stepwise change in the parameters of temperature-force loading (unloading). The problem simulates the stress-strain state of a surface-hardened cylinder (rod), the end section of which is rigidly fixed on a disk rotating at a constant angular velocity.The technique includes a method for reconstructing the fields of residual stresses and plastic deformations and a method for calculating the relaxation of residual stresses during creep of a rotating cylindrical rod. Since the tensile stresses caused by rotation along the length of the rod do not change in time, the problem of relaxation of residual stresses for a stretched rod at constant stress is solved in each cross section. A detailed numerical study of the effect of the number of revolutions on the rate of relaxation of residual stresses was performed for a shot-hardened cylindrical sample with a radius of 3.76 mm made of EI698 alloy at a temperature of 700 $^\circ$C. Analysis of the calculation results allowed to establish a non-trivial effect, which consists in the fact that the relaxation of residual stresses in sections subjected to axial tensile stresses due to rotation occurs less intensively than in the “tail” section, where the axial load from rotation is zero. The results obtained in this work can be useful in evaluating the effectiveness of surface-plastic hardening of parts under high-temperature creep conditions.