Predicting the likely causes of early crack initiation for extruded aircraft components containing intergranular corrosion

This paper details an experimental and finite element (FE) analysis of the atypical form of intergranular corrosion (IGC) observed in the wing skins of the RAAF and RNZAF P-3 Orion to determine if its presence is likely to cause atypical fatigue crack initiation. An investigation of the local stress concentration of IGC-related features found that it was not the IGC fissure itself that can lead to early fatigue crack initiation, but the pits and corroded inclusions associated with its presence. It was also found that fatigue can initiate sub-surface, however this is limited to a depth of approximately 650 mu m.