Cavity expansion theory applied to the penetration of high speed spheres into weak targets

As a first attempt at identifying a tissue model for use in wound ballistic simulations a study of the deceleration of spherical steel projectiles in soap has been carried out. Experimental data were compared to numerical simulations using AUTODYN-2D, and to predictions given by cavity expansion theory. We found that the AUTODYN-2D simulations show good agreement with experiment when a simple linear equation of state is used in conjunction with a Mieses strength model and a Pmin failure criterion . The predictions made using the cavity expansion theory do not agree well with experiments. A detailed investigation using the numerical model show that the cavity expansion theory agrees well only for the initial phase of the penetration. We believe that the dynamic part of the cavity expansion theory in general is wrong. Based on the theory for laminar flow and observations from AUTODYN-2D simulations, we propose improvements to the cavity expansion theory.