A study of inertia effects under impact loading

In order to understand observed strength enhancements under dynamic impact loading for some cellular materials, the lateral inertia effect during buckling is studied. Indeed, for many cellular structures such as honeycombs, the observed mode is progressive folding. In this paper, brass square tubes are crushed under static and dynamic loading. A direct impact Hopkinson test provides accurate force-displacement recording under impact loading. It shows that there is a significant enhancement of crashing forces whereas the basic material behavior is proved to be rate insensitive. Corresponding numerical simulation using Ls-Dyna leads to the same conclusion. A simple theoretical lateral inertia effect model can explain this enhancement.