Crack initiation in plates with multiple defects

Defects are commonly found on aging aircraft skins and panels and are either caused by localized corrosion or other conditions. Even at low levels of cyclic loading, these localized defects can create a crack, which can lead to catastrophic failure if the crack is not found within a critical period. It has also been found that rivet holes can sometimes be attacked by corrosive environment and then serve as initiation sites under fatigue loading. Fracture experiments were carried out on thin 2024 aluminum plates with different sizes and orientations of small holes and pits to mechanically simulate localized corroded plates and to examine the strength degradation of this material during the corrosion process under static uniaxial tensile loading conditions. Different sizes of holes and pits in varying arrangements were used in fracture experiments to evaluate the diversity of pit topology in corroded plates. Crack initiation locations and stress distribution were evaluated by using boundary integral equation methods. The results showed some interesting variations in material strength depending on the spatial distribution and size of the small defects. This research seeks to analyze the pitting corrosion fatigue problem from a mechanical point of view.