Effect of the residual stresses on the fatigue crack growth behavior at fastener holes

An investigation of the fatigue crack behavior at fastener holes in a low carbon steel before and after cold-expansion and cold-stretching processes is presented. After undergoing cold deformation, compressive residual stresses developed around the hole, therefore the fatigue life of the coldworked specimens was significantly increased compared with that of non-coldworked ones. For determining the residual stress distribution near the edge of the hole finite element methods were used. In the experimental study both coldworked and non-coldworked specimens were tested at the cantilever bending testing machine. Finally, experimentally obtained Δϰ-c (crack length) and c-N (number of cycles) curves are compared with those theoretically obtained. The results are found satisfactory although the discrepancy between them couldnʹt be eliminated. Probable reasons of this discrepancy are discussed.