Energy Absorption System of Thin-Walled Members by Dynamic Crushing Due to Impact Loading

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The construction of an impact testing machine and a system for measurement are attempted to estimate the energy absorption abilities of thin-walled members by impact loadings. The cross-head, of which mass is 18kg, can be accelerated up to 16m/s by both gravity and air pressure, and crushes various types of members. This testing system provides precise measurements of loads applied to the members and the crusing distances.By using this system, circular and polygonal cylinder specimens of metallic materials such as steel or aluminium and fiber reinforced plastics (FRP) are tested in order to study the influences of the shape and the material of specimen on the energy absorption abilities. And also some of the results are compared with those from static crushing tests in order to clarigy the strain rate effect.The difference between the static and impact crushing behaviors of aluminium and non-metallic material specimens is found to be not significant, while the results of steel specimens are strongly affected by the impact velocity. The energy absorption ability of steel specimens by dynamic crushing indicates absolutely much higher than that by static crushing. However it is difficult to determine the dynamic to static ratios in energy absorption abilities because the crushing behaviors in static and dynamic crushing tests show a considerable difference each other which may come from the strain rate effect, inertia force, imperfection sensitivity and so on.The absorbed energy by steel specimens is absolutely higher than aluminium specimens, while the absorbed energy by unit mass shows the advantage to aluminium because the mass density of aluminium is one third of steel. However the energy absorption abilities by unit mass from FRP specimens show higher than even aluminium and it is revealed that FRP will be able to be much more powerful candidate as energy absorption materials.