An efficient energy absorber based on fourfold-tube nested circular tube system

In order to develop an efficient energy absorption structure for protecting equipment against impact and blast shock, this research proposes a fourfold-tube system (FT) consisting of four tubes. Its performance was analyzed experimentally (quasi-static test) and numerical simulation with FE (finite element) models. The deformation mode of the FT system was described in detail by simulation and experiment. With the collapse of the outer tube, the upper inner tubes were pushed towards both sides of the lower inner tube, then three inner tubes are side-by-side in the outer tube and all the tubes were collapsed simultaneously, therefore the stress transmits to the protected structure to be distributed more evenly. As a consequence, the protection capability of the nested tube system is improved by enhancing energy absorption capacity and the robustness of deformation mode. The performance of FT system was compared with that of the triple-tube system (TT) and single-tube system (ST), both the experimental result and simulation results show that the FT system can provide the most stable deformed mode and the highest energy absorption efficiency. For mild-steel nested tube systems, the energy absorbed by the FT system is larger than that of the TT system by 30%, so the defense ability of the FT system is better than the TT system. The deformation mode of the FT system under dynamic load tested experimentally, the results prove that the nested system can works as expected at high strain rates. Finally, the FT system was tested with two type of dynamic loading conditions, impact and blast shock. The results demonstrate that the FT system can provide the most efficient impact force reduction and blast mitigation in protecting the structures from damage under impact and shock wave from the explosion.