Dynamic axial crushing behaviour of thin-walled prismatic structures under high-velocity impact loading: Consideration of strain rate effect

This paper presented a study of the dynamic behavior of mild steel St37 thin-walled columns subjected to high-velocity axial impact. Mild steel St37 was a strain rate sensitive material since its stress-strain relation depent on the rates of loading. Two groups of thin-walled columns were used in this study, i.e. one group of material model had strain rates with up to 100 s-1 (group 1) and another had strain rates with up to 4500 s-1(group 2). The study was conducted by using theoretical solution and finite element analysis for impact speeds of 20 m/s, 30 m/s, 40 m/s and 50 m/s. The instantaneous and mean crushing forces of the thin-walled columns were predicted and compared in terms of the effect of strain rates and initial velocity impact conditions. For impact speed less than 20 m/s, the results shown that there were no significant differences with respect to crushing forces and energy absorption capability for both materials of (group 1) and (group 2). However, for impact speed higher than 20 m/s, the structural model of group 2 with strain rates up to 4500 s-1 pointed out higher crushing forces, peak force and energy absorption than those in group 1. Consequently, the impact analysis under high-velocity impact should use high strain rates material model. Moreover, the comparison between theoretical and numerical studies also shown a good agreement in terms of mean crushing forces at various high-velocities impact.