Ballistic impact behavior of AA6061 plates with different thicknesses impacted by hemispherical-nosed projectiles

This research investigated the ballistic behavior of 6061 aluminum alloy with varying thicknesses subjected to hemispherical-nosed projectiles. It evaluated the necessity of incorporating nonlinear strain rate and temperature sensitivities in strength model for ballistic simulations, and analyzed the failure mechanisms of targets with two typical thickness. Ballistic tests were performed on 1.5 mm and 4 mm thick targets to determine ballistic resistance and failure modes. The Johnson-Cook (JC) failure model was employed, with simulations conducted using two strength models: the JC model and the modified JC (MJC) model. The experimental results revealed different failure modes for the two target thicknesses. The 1.5 mm target exhibited a disk-shaped plug and a short petal-like hole, whereas the 4 mm target displayed a mushroom-head plug and circumferential spalling at the rear hole. Numerical simulations showed that failure initiated as cracks on the rear surface, with tension dominating the failure process. Increased target thickness resulted in more complex failure paths, leading to variations in perforation and plug formation. Crack propagation and ductile perforation behavior significantly influenced failure modes, energy dissipation, and ballistic resistance. Simulations using the MJC strength model, which accounted for nonlinear strain rate and temperature sensitivities, showed better agreement with experimental results in terms of ballistic resistance, failure modes, and perforation mechanisms, particularly for the 4 mm target, compared to those using the JC model.