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Dynamic Crushing of Voronoi Honeycombs: Local Stress-Strain States

Dynamic stress-strain states in Voronoi honeycombs are investigated by using cell-based finite element models. Two different loading scenarios are considered: the high-constant-velocity compression and the direct impact. The 2D local engineering strain fields are calculated. According to the feature of shock front propagation, the 1D distribution of local engineering strain in the loading direction is deduced from the 2D strain fields, which provide evidences of the existence of discontinuities at shock front in cellular materials and thus enhance the basis of the continuum-based shock models. A method to quantitatively clarify the local stress-strain states ahead of and behind the shock front is developed. The results show that the dynamic stress-strain states in the densification stage obtained from both loading scenarios are different from the quasi-static stress-strain relation. The stress ahead of the shock front obtained from the high-constant-velocity compression scenario is slightly smaller than the quasi-static yield stress, but that obtained from the direct impact scenario is larger than the quasi-static yield stress. The possible mechanisms of deformation and wave propagation are explored.