Ballistic Characterization Of A Typical Military Steel Helmet

In this study the ballistic limit of a steel helmet against a FMJ 919 mm caliber bullet is estimated. The helmet model is the typical polish helmet wz.31.The helmet material showed high strength low alloy steel material of 0.28 carbon content and 9.125 kgm2 areal density. The tensile test according to ASTM E8 showed a tensile strength of 1236.4 MPa .The average hardness value was about HV550. First shooting experiment has been executed using a 9 mm pistol based on 350 ms muzzle velocity at 5m against the simply supported helmet complete penetrations rose in this test were in the form of cracks on the helmet surface and partial penetrations were in the form of craters on the surface whose largest diameter and depth were 43 mm and 20.2 mm consequently .The second experiment was on a rifled gun arrangement 13 bullets of 919 mm caliber were shot on the examined simply supported steel helmet at a zero obliquity angle at different velocities to determine the ballistic limit velocity V50 according to MIL-STD-662F. Three major outcomes were revealed 1 the value V50 which found to be about 390 ms is higher than the one found in literature 360 ms German steel helmet model 1A1. 2 The smallest the standard deviation of the mixed results zone data the most accurate the ballistic limit is. 3Similar to the performance of blunt-ended projectiles impacting overmatching targets tD near 11 or larger It was found that the dominating failure mode of the steel helmet stuck by a hemispherical-nose projectile was plugging mode despite of having tD ratio of about 19 undermatching.