THE EFFECT OF RESIDUAL STRESSES INDUCED BY SHOT‐PEENING ON FATIGUE CRACK PROPAGATION IN TWO HIGH STRENGTH ALUMINIUM ALLOYS

Abstract

Abstract— The crack initiation lives of peened specimens of aluminium alloys 7010 and 8090 are shorter than those of unpeened specimens. This is caused by the acceleration of crack initiation due to stress concentration in the rough peened surface, especially at fold‐like defects. The crack growth rate in peened specimens is significantly reduced with increasing Δ K , i.e. with increasing crack length. At a crack length of approximately 0.3 mm this trend is reversed and the crack growth rate rapidly increases and attains the same level of crack growth rate as that in unpeened specimens. The point of smallest crack growth rate roughly corresponds to the point of maximum residual stress. The crack growth rate in a peened specimen has been modelled by assuming the effect of residual stress reduces to the equivalent stress ratio. The predicted results agree well with the experimental data.