Abstract
The influence of residual stresses on the fatigue strength of specimens with a punched hole was investigated in two grade high strength steel sheets. Punching induces tensile and compressive residual stresses in the circumferential direction near the edge of the hole. Tensile residual stress exists in the area of shear drop and the area of fractured surface. Proper conditions of stress relief heat treatment were selected to avoid softening around the hole. The increase of fatigue strength by the heat treatment should depend on the decrease of tensile residual stresses near the edge of the hole.
