Fatigue-life calculations on pristine and corroded open-hole specimens using small-crack theory

This paper uses a plasticity-induced crack-closure model and small-crack theory to calculate the fatigue lives of 2024-T3 aluminum alloy sheet specimens with open holes subjected to cantilever (R = −1) bending loads. The bending specimens had three drilled holes that were either pristine or exposed to outside weather conditions at various locations for 3–12 months. The exposed specimens developed various levels of corrosion pits in and around the holes. These pre-corroded specimens were then returned to the laboratory and fatigue tested under laboratory-air conditions with cantilever bending loads. The present paper uses fatigue-crack growth with an equivalent-initial-flaw-size (EIFS) to fit the fatigue behavior of the exposed specimens. Improved stress-intensity factor equations for a corner crack at the edge of an open hole under remote bending were used to make the fatigue-life calculations. The EIFS values agreed well with the median corrosion-pit depths measured on the exposed specimens with moderate corrosion. For one case of severe corrosion, the EIFS value was much larger than the measured pit depth.