The dynamic compressive behavior of armor structural materials in split Hopkinson pressure bar test

Abstract

High strain rate-dependent deformation behaviors are important in design and optimization of armor structural materials. Herein, the static tensile and the dynamic compressive behaviors of the practical materials including Al5083, rolled homogeneous armor steel and tungsten heavy alloy were investigated by means of a universal testing machine and a split Hopkinson pressure bar apparatus, respectively. The test was performed at high strain rates (1200-3100 s(-1)) to obtain a detailed understanding of the responses of the materials. A finite element analysis was then carried out using an elastic-plastic failure material model considering a user-defined parameter determined from the split Hopkinson pressure bar tests. Both flow and peak stresses of the materials were different corresponding to the mechanical properties and strain rates. The dynamic yield stresses are generally larger than static yield stresses, particularly in Al5083. As shown in the results, the experimentally obtained true stress-strain behaviors give a good agreement with those from finite element analyses. In addition, observations of the impacted zone in the specimen showed that a few cracks propagated along the specimen's original periphery. In order to determine the level of deformation, strain rate sensitivity, m, at strain of 0.1 was also calculated for all materials; rolled homogeneous armor steel and tungsten heavy alloy had lower strain rate sensitivity than Al5083. The proposed procedure shows proper agreements between numerical predictions and experimental results such as stress-strain relations, peak stresses and deformation. The methodology coupled with the experimental data reflecting the dynamic compressive properties provides a more accurate prediction of the strain rate-dependent behavior of armor structural materials.