On the asymmetrical material flow in metal specimens under dynamic compression with Hopkinson bars

Modeling of the asymmetrical material flow in the specimen during a Hopkinson bar compression test is proposed, based on comparative results between numerical simulation using AUTODYN-2D and experimental tests applied to metals with different phase structures (copper, aluminum, iron and titanium). Among three main material flow regions, only one could be considered as valid for a material investigation. The non-valid rim zone results in a flow process at the specimen impact front side, which is at first radial then, when emerging from the gap between the two bars, moves towards the specimen rear face. Metallographic investigations indicate that the microstructure for Fe and especially Ti is hard to define. The three material flow regions can be outlined by following the observed flow l ies for A1 or shear bands for Ti.