Analysis for post-impact tensile-tensile fatigue damage of 2024-T3 sheets based on tests, digital image correlation (DIC) technique and finite element simulation

In order to investigate the effect of low velocity impact damage on fatigue performance of aluminum alloy 2024-T3 thin sheets used in the airframe, the digital image correlation (DIC) analysis was conducted to evaluate fatigue failure of specimens containing various impact damages induced by hemispherical and U-shaped inserts. 2D and 3D strain fields calculated from digital speckle images were applied to analyze the fatigue crack nucleation and propagation. The effects of impact energy, dent dimension and insert shape on the fatigue life are discussed according to the experimental data which could be fitted to a 2-order empirical equation. Fatigue crack nucleation is intensively dominated by the dent geometry resulting from the impact process, the crack initiated around the dent propagates by a combined failure mode of I and III under dynamic loading. The dent could redistribute the strain field on the surface of dented specimens through DIC nephogram analysis. In addition, the simulation based on ABAQUS/Explicit could provide a reliable strain field distributed on the concave surface of dented specimens, while the fatigue life prediction acquired from Fe-safe shows close agreement with experimental data, which could be further used in fatigue life evaluation of impacted components.