An Experimental Study of the Dynamic Elasto-Plastic Contact Behavior of Dimer Metallic Granules

Studying the dynamic elasto-plastic contact behavior of dimer metallic granules, defined as contacting beads of either different size or material, is important for understanding the behavior of heterogeneous granular systems such as periodic or multi-phase systems. In this paper, the dynamic contact response of dimer bead pairs was experimentally studied using a split Hopkinson pressure bar apparatus. Two types of dimer combinations were subjected to dynamic loading: dimers with the same bead size but different materials (material dimers), and dimers of the same material but different size (size dimers). Dynamic elasto-plastic contact force-displacement curves, post mortem images of yielded contact area, residual contact deformation, and energy absorption during the impact process were measured in each case. It was found that the dynamic contact behavior of the material dimers is controlled by the material with lower yield strength, and can be well described by existing elasto-plastic contact models. In contrast, the size dimers show a complex deformation process that cannot be described by current theoretical models. It was also seen that the strain rate sensitivity of the material itself affects the dynamic yield process of size dimer pairs, and their radius ratio shows a linear effect on the residual deformation and energy transmitted ratio.