The effective strength of metallic plates perforated by rigid projectiles

The work presented in this paper addresses the issue of determining the appropriate values for the dynamic strength of metallic plates perforated by rigid sharp-nosed projectiles. This issue is especially important for materials which exhibit strain hardening behavior, to either a minor degree (like the various aluminum alloys), or to a large degree (like the 304 L stainless steel). Using both numerical simulations and perforation tests, we demonstrate the validity of our proposed technique to determine the effective dynamic strength values for metallic plates. Namely, they should be determined through the dynamic stress-strain curves as obtained by compressive Kolsky bar tests, with specimens taken from the plates, at rates in the range of 5000-10,000 s−1 and at a strain of 0.27. This “recipe“ is validated by the results we obtained from perforation experiments with the hard steel cores of 7.62 mm armor-piercing projectiles, on rolled homogenous armor (RHA) and 304 L stainless steel plates, as well as on 6061-T651 aluminum and C-101 copper plates. We also demonstrate that the ballistic limit velocities of metallic plates depend only on their dynamic compressive strength and not on their density, in agreement with a previously published numerically-based perforation model. Finally, we show that these effective dynamic strengths can be used to characterize the target material in numerical simulations for deep penetrations studies.