Measurement and prediction of fatigue crack growth from cold expanded holes Part 1: The effect of fatigue crack growth on cold expansion residual stresses

Abstract

Cold expansion of holes introduces beneficial compressive residual stresses that retard cracking in fatigue loaded material. Using X-ray diffraction measurements, it was found that when the fatigue protection was exceeded and crack initiation and growth occurred, the original residual stress distribution was significantly modified. The change of residual stresses due to fatigue crack growth was investigated by considering the geometrical discontinuity in the material and the small-scale plasticity accompanying fatigue crack propagation. Fatigue crack growth simulation by cutting a slot using electrodischarge machining showed that the cold expansion residual stresses were affected much more by a slot than by an actual fatigue crack.