Optimised design of nested circular tube energy absorbers under lateral impact loading

Arrangements of mild steel (DIN 2393) nested tubes were laterally crushed by dynamic loading. The tests were performed with impact velocities ranging between 3 and 5 m/s, using a fixed mass impinging onto the specimens under the influence of gravity. Two arrangements of nested tube systems were considered; one standard and one optimised design. Their crushing behaviour and energy absorption capabilities were analysed experimentally and simulated numerically using the explicit code LS-DYNA. Results from the numerical analyses were compared against those obtained from experiments. An over-prediction in force-deflection responses was obtained from the numerical code. An attempt was made to explain this inconsistency on the basis of the validity of strain rate parameters used in the Cowper Symonds relation. It was shown that the optimised energy absorber exhibited a more desirable force-deflection response than the standard arrangement due to a simple design modification which involved mild steel cylindrical dampers.