Terminal ballistics of metallic projectiles versus metallic targets: Correlating empirical, analytical, and numerical models via Effective Flow Stress (EFS)

Over 8000 terminal ballistics data points were reviewed from numerous data sets. No data set that was considered included all of the information needed to fully analyze the documented experiments. In some cases material properties were not adequately recorded. In other sets the impact conditions were not adequately measured and documented; the range of impact conditions was too narrow to draw general conclusions; or some other problem existed. The author found one data set that was incomplete, but adequate for the purposes of this study and analyzed it using similitude analysis techniques, analytical penetration models, and non-linear regressions. This lead to a new interpretation of a non-dimensional Pi term developed using similarity methods as prescribed by the Buckingham-Pi Theory that eliminates the need to have constitutive similarity of dissimilar or scaled target materials for the problem considered. The new interpretation led to the definition of a pseudo property that the author calls Effective Flow Stress (EFS). There is a specific relationship between the EFS and the target resistance and it is noted that the EFS is weakly dependent on the crater radius and the penetration rate as well as the dynamic constitutive properties of the target material. For long rod eroding penetration, it is noted that the EFS is sufficiently constant over the course of a penetration event and even over a relatively wide range of penetration events, that a single value can typically be used for a wide range of impact velocities for a given projectile size.