Impact energy absorption of metal foam with the controlled microstructure under dynamic loading

摘要

Metallic foams are expected to use for the impact energy absorber because of their deformation characteristics where almost constant compressive stress appears in a wide range of strain, well-known as the plateau regime. It is very important to know the strain rate dependence of the plateau stress or the impact energy for applications to a suitable design of automotive components. Limited data are, however, available for the mechanical response of metallic foams under dynamic loading comparing with polymer foams. In this study, the absorbed energy of open-celled aluminum and magnesium foams with the relative density of 0.03 ~ 0.065 is evaluated at a dynamic strain rate ～10~3 s~(-1) in compression by using the split Hopkinson pressure bar apparatus. In order to investigate the effect of microstructure in the solid metals, solution treatment and aging are performed to all the specimens and then examined for the same strain rates. As a result, plateau stress of all the as-cast metallic foams showed the strain rate dependence in comparison with mat at a quasi-static strain rate of 1x10~(-3) s~(-1), while those of solution treated and aged foams are independent of strain rate. Therefore, it is possible to control the mechanical response of the metallic foams owing to the ductility of base metals as the factor of energy absorption.