Release and redistribution of residual stress in the welded turbine rotor under service-type loadings

Welding residual stress relaxation and migration behavior in the welded turbine rotor was studied by using thermal elastic-plastic finite element method under the fatigue and creep loadings. The effect of solid-state phase transformation on the generation of residual stress during welding process was involved. Results reveal that the increase of welding pass number will reduce the peak of residual stress and the width of heat affected zone (HAZ). Under the repeated loadings, the welding residual stress is largely released after the first cycle of start-up and shut-down with a residence time. In addition, such a relaxation mainly depends on the temperature, the initial level of residual stress and the residence time of steady operation. Compared to the contribution of alternating load induced during the start-up and shut-down operation, the relaxation of residual stress is mainly ascribed to the creep mechanism.