A preliminary study on the perforation resistance of high-strength steel plates

Thin plates of high-strength steel are frequently being used in ballistic protection systems. In this study, the perforation resistance of three different high-strength steel alloys impacted by 7.62 mm AP projectiles has been determined and compared against each other. The considered alloys are Weldox 500 E, Hardox 400 and Domex Protect 500. The yield stress in Domex Protect 500 is almost three times the yield stress in Weldox 500E, while the opposite trend is found regarding strain to fracture in uniaxial tension. Perforation tests have been carried out using adjusted ammunition to determine the ballistic limit velocity of the steels using 6 + 6 = 12 mm thick targets. Moreover, a material test programme including high strain rate tests in a split-Hopkinson tension bar was carried out in order to be able to calibrate a proper constitutive equation and fracture criteria. Here, a simplified identification procedure was used together with a modified Johnson-Cook constitutive relation and the Cockcroft-Latham fracture criterion since it is considered important to limit the number of material tests in design. Finally, results from 2D axisymmetric numerical simulations using the non-linear FEM code LS-DYNA are included, and the different findings are compared.