Damage mechanism in high hardness armor (HHA) steel subjected to V50 ballistic impact

A high hardness armor (HHA) steel plate was subjected to a standard V50 ballistic impact test. Microstructural evolution leading to deformation and perforation of the plates during projectile penetration is investigated. Penetration of the steel plate by the projectile is promoted by shear strain localization and occurrence of adiabatic shear bands which were observed around the perforations. Cracking of the shear bands triggered the failure and perforation of the steel plate during the ballistic impact. The primary transformed bands enveloping the projectile has an average thickness of about 55 μm, while narrower secondary shear bands of about 12 μm wide branched out of the primary band leading to secondary cracking which propagated from the wall of perforation into the armor plate