Dynamic Deformation of Copper-Jacketed Lead Bullets: Experiments and Modeling
Steven P. Mates
The development of high fidelity simulations of a bullet impacting soft body armor, motivated by the need for improved armor designs and performance standards for law enforcement, requires accurate material models for both the armor and the deformable bullet. This paper focuses on the behavior of deformable bullets. Specifically, we examine the ability of a literature-derived material model to predict the dynamic deformation of a 0.4 caliber copper-jacketed lead bullet of a type that is specified as a test round the current NIJ Standard 0101.04 governing soft body armor performance. A direct-impact Kolsky bar test is performed that subjects the bullet to an impact velocity of 15.3 m/s and an impact energy of 62.5 J, or about 10 % of the impact energy required in the NIJ Standard 0101.04 for testing Type IIA body armor with this bullet. An advanced high speed 3D digital image correlation technique is used to optically measure the full-field deformation history of the bullet during the test. Load-time data are also recorded. The results are then compared to finite element simulations, which indicate that literature-derived material constants for the jacket are not able to reproduce the deformation behavior of the bullet. A model sensitivity analysis is carried out to determine the most influential material parameters using design-of-experiments methods, and an improved set of parameters is determined that points to a much stronger jacket response.
September 13-17, 2010
digital image correlation, finite element modeling, Kolsky bar, lead bullets, soft body armor