Can pitting corrosion change the location of fatigue failures in aircraft?

• A Monte Carlo model was developed to predict the fatigue life of 7010-T7651.
• The material was modeled as low-kt specimens in pitted and uncorroded states.
• It predicted median and lower bound lives of corroded 7010 within a factor of two.
• The model also predicted the location of pitting and inclusion initiated cracks.
• The predicted sites agreed well with the results of an experimental trial.

In this paper we hypothesize that pitting corrosion can alter the location of fatigue failures in aircraft. This is in addition to the reductions in fatigue life it causes. The investigation began by developing a predictive Monte Carlo model of the fatigue behavior of low-kt specimens of the aluminum alloy 7010-T7651. The model’s fatigue life predictions were an excellent match to experimental fatigue life data from previous DSTO research for the same specimen geometry and material. The model was then used to predict the proportion of failures due to pitting corrosion as a function of the location of the corrosion strike. These predictions were compared to the results of an experimental trial of specimens which had been corroded at the same offset locations. The predicted and experimental proportions of failures were in close agreement. The paper concludes with a discussion of an integrated model of corrosion pit nucleation and growth followed by fatigue crack growth to failure. The purpose of this integrated model is to give the Royal Australian Air Force an end-to-end model to predict the damaging effects of pitting corrosion on aircraft structural integrity.