Dislocation microstructures in explosively deformed hard materials

Merala, T.B.; Chan, H.W.; Howitt, D. G.; Kelsey, P.V.; Korth, G.E.; Williamson, R.L.

doi:10.1016/0025-5416(88)90510-1

Cited by 17 publications

(6 citation statements)

References 6 publications

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“…We note that while the maximum compressive loadings explored in this work are ∼12 GPa, below the experimentally measured elastic limit (Dandekar 2004), it has been observed by Merala et al (1988) that significant dislocation structures can evolve under increased shock loadings (∼23 GPa). Cohesive relations govern grain boundary crack initiation and propagation.…”

Section: Modeling Approachmentioning

confidence: 89%

A grain-scale study of spall in brittle materials

Foulk

Vogler

2010

Int J Fract

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The evolution of spall for a brittle material is investigated under variance of anisotropy, grain boundary fracture energy, and loading. Because spall occurs in the interior of the specimen, fundamental studies of crack nucleation and growth are needed to better understand surface velocity measurements. Within a cohesive approach to fracture, we illustrate that for anisotropic materials, increases in the fracture energy cause a transition in crack nucleation from triple-points to entire grain boundary facets. Analysis of idealized flaws reveals that while crack initiation and acceleration are strong functions of the fracture energy, flaws soon reach speeds on the order of the Rayleigh wave speed. Finally, simulated surface velocities of spalled configurations are correlated with microstructural evolution. These fundamental studies of nucleation, growth, and spall attempt to link atomic separation to the macroscopic spall strength and provide a computational framework to examine the evolution of spall and the impact on the simulated surface velocity field.

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Section: Modeling Approachmentioning

confidence: 89%

A grain-scale study of spall in brittle materials

Foulk

Vogler

2010

Int J Fract

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“…The microplasticity is considered as a viable mechanism of inelastic deformation in ceramics under shock compression based on the results of microscopy studies of Merala et al 6 and Longy and Cagnoux 7 on ceramic samples recovered from shock-recovery tests. II A͒, and three-dimensional ͑3D͒ nonlinear constitutive models for anisotropic crystal elasticity and intragranular microplasticity ͑Sec.…”

Section: Modeling Methodologymentioning

confidence: 99%

Microdamage in polycrystalline ceramics under dynamic compression and tension

Zhang

Feng

et al. 2005

Journal of Applied Physics

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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.

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“…Superscript i corresponds to a particular slip system with resolved shear stress i . Merala et al 2 noted that secondary slip on prism planes may occur in shock-loaded hexagonal SiC, and this mechanism was considered in the simulations of Zhang et al 40 At temperatures below 1400 K, partial dislocations are favored over full dislocations, with leading partials more mobile than trailing partials in 4H-and 6H-SiC. 16,42,79 In ␣-SiC, Q may depend on electric current to account for lowering of the energy barrier to dislocation migration under bias voltage.…”

Section: Inelastic Shear: Plastic Slip and Fracturementioning

confidence: 99%

“…[28][29][30][31][32][33][34][35][36] Shock physics experiments on polycrystals of ␣-SiC have indicated that SiC maintains significant strength above the Hugoniot elastic limit ͑HEL͒ and suggest that deformation by dislocation generation and motion may occur in SiC under high confining pressures, even near room temperature. 2 The occurrence of plasticity in SiC has been noted in indentation experiments 38 and atomistic simulations. 2 The occurrence of plasticity in SiC has been noted in indentation experiments 38 and atomistic simulations.…”

Section: Introductionmentioning

confidence: 97%

Modeling nonlinear electromechanical behavior of shocked silicon carbide

Clayton

2010

Journal of Applied Physics

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A model is developed for anisotropic ceramic crystals undergoing potentially large deformations that can occur under significant pressures or high temperatures. The model is applied to describe silicon carbide (SiC), with a focus on α-SiC, specifically hexagonal polytype 6H. Incorporated in the description are nonlinear anisotropic thermoelasticity, electrostriction, and piezoelectricity. The response of single crystals of α-SiC of various orientations subjected to one-dimensional shock loading is modeled for open- and short-circuit boundary conditions. The influences of elastic and electromechanical nonlinearity and anisotropy on the response to impact are quantified. For elastic axial compressive strains less than 0.1, piezoelectricity, electrostriction, and thermal expansion have a negligible influence on the mechanical (stress) response, but the influences of nonlinear elasticity (third-order elastic constants) and anisotropy are not insignificant. The model is extended to incorporate inelastic deformation and lattice defects. Addressed are Shockley partial dislocations on the basal plane and edge dislocation loops on the prism plane, dilatation from point defects and elastic fields of dislocation lines, and cleavage fracture. The results suggest that electric current generated in shock-loaded α-SiC crystals of certain orientations could affect the dislocation mobility and hence the yield strength at high pressure.

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Dislocation microstructures in explosively deformed hard materials

Cited by 17 publications

References 6 publications

A grain-scale study of spall in brittle materials

A grain-scale study of spall in brittle materials

Microdamage in polycrystalline ceramics under dynamic compression and tension

Modeling nonlinear electromechanical behavior of shocked silicon carbide

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