Modeling the ballistic impact performance of two aluminium alloys

Thin plates (4.75 mm) of two aluminum alloys, 6061-T6 and 7075-T6, were impacted with a Sierra, lead-filled bullet. The impact velocities ranged from approximately 270 m/s to 370 m/s with the higher velocities approaching the ballistic limit of the aluminum plates. The 7075-T6 aluminum plates exhibited less deformation than the 6061-T6 plates at the same impact velocity. The in-plane back surface strains were determined by post-test analysis of a grid pattern, placed on the non-impacted surface of the plates prior to testing. The deformation behavior of the plates was further investigated using the CTH and EPIC wavecodes. CTH is an Eulerian code used to model the performance of materials at large deformations and high strain rates. EPIC is a Lagrangian code with capabilities for modeling high strain rate materials behavior, as well. The modeling results are used to explain the observed differences in deformation behavior of the impacted Al-6061-T5 and Al-7075-T6 plates.