Certain rules of the change in residual stresses in cyclic loading in relation to their initial level and stress concentration

Abstract

1. It was established that under the action of a cyclic load a change in the initial tensile and compressive residual stresses occurs and in specimens without a weld residual stresses are formed in the zones of stress raisers. In all three cases these changes occur primarily in the first load cycle. Subsequent cycles cause significantly smaller changes and the level of residual stresses may be assumed to be practically steady. 2. Stress concentration has a significant influence on the intensity of the change in initial residual stresses. Its action on the change in residual tensile stresses appears in the whole investigated range of values of external load while in the case of original residual compressive stresses starting with the level of external load at which the maximum stresses in the zones of stress raisers reach the yield strength of the material. 3. The influence of initial residual stress on the fatigue resistance of structural elements is determined by the difference in the levels of steady residual stresses in the zones of stress raisers in the presence of initial residual stresses and without them.