FATIGUE LIFE AND SURFACE CRACK PENETRATION BEHAVIOR OF AN ALUMINUM-ALLOY

Fatigue life and crack retardation behaviour after penetration were examined experimentally using CT specimens and surface pre-cracked specimens of aluminium alloy 5083-0. The fatigue crack shape before penetration is almost semicircular, and the measured aspect ratio is larger than the value obtained by calculation using K values proposed by Newman-Raju. It was found that crack growth behaviour on the back side after penetration is unique, and can be divided into three stages. The Wheeler model retardation parameter was used successfully to predict crack growth behaviour after penetration. By using a crack propagation rule, the change in crack shape after penetration can be evaluated quantitatively.