Microdamage in polycrystalline ceramics under dynamic compression and tension

Abstract

In-grain microplasticity and intergranular microdamage in polycrystalline hexagonal-structure ceramics subjected to a sequence of dynamic compression and tension are studied computationally using the Voronoi polycrystal model, by which the topological heterogeneity and material anisotropy of the crystals are simulated explicitly. The constitutive modeling considers crystal plasticity by basal slip, intergranular shear damage during compression, and intergranular mode-I cracking during tension. The model parameters are calibrated with the available shock compression and spall strength data on polycrystalline ␣-6H silicon carbide. The numerical results show that microplasticity is a more plausible micromechanism for the inelastic response of the material under shock compression. On the other hand, the spallation behavior of the shocked material can be well predicted by intergranular mode-I microcracking during load reversal from dynamic compression to tension. The failure process and the resulting spall strength are, however, affected strongly by the intensity of local release heterogeneity induced by heterogeneous microplasticity, and by the grain-boundary shear damage during compression.

Novel Processing of Unique Ceramic-Based Nuclear Materials and Fuels

“…Since the model is two dimensional, this area fraction covered by grains becomes the volume fraction of crystalline material in the polycrystalline model. This approach has been used by Zhang et al [177] to create grain boundary phase in finite element modeling of polycrystalline silicon carbide.…”

“…A centroidal Voronoi tessellation (CVT) is a Voronoi tessellation of a given set such that the associated generating points are centroids of the corresponding Voronoi regions. Voronoi tessellation has been extensively used in materials science for modeling microstructure of randomly distributed grains in polycrystalline materials [154,155,[175][176][177].…”

Modeling nonlinear electromechanical behavior of shocked silicon carbide

“…8,13,37 Large dislocation densities have been measured in ␣-SiC subjected to explosive shock loading. 39 Zhang et al [40][41][42] developed a crystal plasticity model for hexagonal SiC incorporating dislocation glide on basal planes, possible slip on prism planes, and failure at amorphous regions in the vicinity of grain boundaries. 39 Zhang et al [40][41][42] developed a crystal plasticity model for hexagonal SiC incorporating dislocation glide on basal planes, possible slip on prism planes, and failure at amorphous regions in the vicinity of grain boundaries.…”

“…2 The occurrence of plasticity in SiC has been noted in indentation experiments 38 and atomistic simulations. Computational studies of Zhang et al 42 suggest that basal slip is more viable than fracture when considering longitudinal and lateral stress profiles measured in impact experiments on polycrystals. Computational studies of Zhang et al 42 suggest that basal slip is more viable than fracture when considering longitudinal and lateral stress profiles measured in impact experiments on polycrystals.…”

“…39 Zhang et al [40][41][42] developed a crystal plasticity model for hexagonal SiC incorporating dislocation glide on basal planes, possible slip on prism planes, and failure at amorphous regions in the vicinity of grain boundaries. [40][41][42] Isolated slip of leading partial dislocations was not considered explicitly, nor were temperature effects such as adiabatic heating, thermal expansion, and thermally enhanced dislocation mobility. Nontextured polycrystals were addressed; hence, electromechanical interactions were omitted in numerical simulations.…”