Effective Depth-of-Penetration Range Due to Hardness Variation for Different Lots of Nominally Identical Target Material

Abstract

The effect of small variations of target hardness on the depth of penetration for long rod projectiles (L/D = 15) penetrating into semi-infinite armor steel targets (nominally 280 BHN–330 BHN) was investigated. The work consisted of hardness testing, 17 ballistic experiments (1250 m/s–1780 m/s) and data analysis. A linear regression analysis shows that a target hardness increase within the given range may result in a reduction of penetration depth of about 5.8 mm at constant velocity (-12 % at an impact velocity of 1250 m/s). A multiple linear regression analysis including yaw angle and impact velocity shows that small variations of those provide a smaller variation of the penetration depths than a typical variation of target hardness. The overwhelming part of the variation is to be attributed to hardness effects. For nominally identical target material, the target hardness influences the ballistic results more severely than the typical scatter in impact conditions.