Constitutive model for Armox 500T and Armox 600T at low and medium strain rates

Constitutive Model for Armox 500T and Armox 600T at Low and Medium Strain Rates High-hardness armour steels provide a high-performance protection at a relatively low cost and is an interesting material for movable shelters. Material testing is important both because of the need for understanding the dynamic material behaviour and as input in numerical simulations of ballistic events. In this report, experiments conducted on Armox 500T and 600T, two high hardness armour steels manufactured by SSAB in Oxelösund, Sweden. The experiments have been conducted at various strain rates and temperatures and the parameters in the strength models according to Johnson & Cook and variants of the Johnson & Cook proposed by Weerasooriya and Huang and Liang respectively, and Zerilli & Armstrong have been fitted to the experimental data. To be able to include data collected after necking, the neck was photographed during the test and stress and strain corrected according to Bridgman. Experiments were conducted to test the isotropy of the steel and quasi-static yield stress and rupture strength. The experimental data was fitted to the dynamic strength models following different fitting procedures. The different procedures give different results and these are compared and checked for unphysical behaviour. Plotting the results of all strength models and procedures show that the differences between different strength models and procedures are significant. The results from the experiments are to some extent compared with data found in the literature. Both the experiments and the literature shows that high-hardness martensitic armour steels have low strain-rate hardening at medium strain-rates, ? < 1000/s, compared to for example nitrogen alloyed steel.