Effect of staggered holes with multi-site damage on fatigue performance based on tests, DIC technique and numerical calculations

The fatigue performance was investigated numerically and experimentally of 2024-T3 Al-clad sheet with staggered hole arrangement and multi-sites damage (MSD), which is mainly used in aging aircraft fuselage skin. Firstly, the influences of row spacing, column spacing and inter-crack direction on fatigue life were studied. Then, the strain nephogram and crack path were analyzed with the assistance of digital image correlation (DIC) technique. Finally, a numerical solution for the specimens with staggered holes and MSD was developed based on the combination of ABAQUS and Paris formula. The results show that with the increase of row spacing, the fatigue life of MSD specimens with fixed column spacing increases first and then decreases. In the case of fixed row spacing, the fatigue life of specimens increases with the increase of column spacing. The arrangement parameter a is introduced to reveal the crack propagation form. Meanwhile, the common form of fracture is through the upper row of hole. In addition, the distribution of rivet holes has an effect on the initiation life of fatigue cracks in the structure with MSD, especially the row spacing. The numerical solution could provide a conservative prediction of fatigue lives, and the predicted error is less than 5% for cases of HH-2g24.