Dynamic compressive behaviour of Mg foams manufactured by the direct foaming process

Abstract

Increasing interest in lightweight Mg foams for the potential impact energy dissipation application in transport industry requires a good understanding of the dynamic deformation and failure process of the foam. The split-Hopkinson pressure bar technique, combined with high speed photography and post-test scanning electron microscopic examination, was applied to investigate the dynamic behaviour of closed-cell Mg foams manufactured by the direct foaming process. The deformation and failure behaviour at dynamic strain rates was then compared to the quasi-static response. It was found that the fracture of Mg cell walls is brittle and strain rate sensitive. Compared to quasi-static compression, a large quantity of short macro-cracks evolves in cell walls at dynamic strain rates, causing more fragments and thus dissipating more impact energy. The rate dependent fracture mechanisms in cell walls significantly affect the strain rate sensitivity of bulk properties of the foam such as peak stress, plateau stress and energy dissipation capacity.