Fatigue crack growth from corrosion damage in 7075-T6511 aluminium alloy under aircraft loading

This paper investigates the growth behaviour of fatigue cracks initiated at corrosion pits in laboratory coupons of 7075-T6511 aluminium alloy subjected to a transport aircraft loading spectrum. Corrosion pits were artificially introduced by exposing the coupons to EXCO solution for a variety of periods to produce corrosion damage varying from mild to severe. In general, the presence of corrosion damage reduced the fatigue lives of components to a severe extent. It was found that the depth of the corrosion pit was a suitable parameter for characterizing the corrosion damage and for predicting the fatigue life of the coupons using commercial fatigue crack growth software. It is suggested that for practical purposes the size of the deepest corrosion pit in the area of corrosion damage on an aircraft, or similar structure, can be used as the metric for predicting fatigue life.