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Research Papers

A Nonlinear Thermomechanical Model of Spinel Ceramics Applied to Aluminum Oxynitride (AlON)

[+] Author and Article Information
J. D. Clayton

Impact Physics, US Army Research Laboratory, Aberdeen Proving Ground, MD 21005-5066jclayton@arl.army.mil

J. Appl. Mech 78(1), 011013 (Oct 20, 2010) (11 pages) doi:10.1115/1.4002434 History: Received December 10, 2009; Revised August 17, 2010; Posted August 24, 2010; Published October 20, 2010; Online October 20, 2010

A continuum model is developed for describing deformation and failure mechanisms in crystalline solids (ceramics and minerals) with the cubic spinel structure. The constitutive model describes the response under conditions pertinent to impact loading: high pressures, high strain rates, and, possibly, high temperatures. Nonlinear elasticity, anisotropy, thermoelastic coupling, dislocation glide, twinning, shear-induced fracture, and pressure-induced pore collapse are addressed. The model is applied to enable an improved understanding of transparent ceramic aluminum oxynitride (AlON). Calculations demonstrate an accurate depiction of hydrostatic and shear stresses observed experimentally in shock-loaded polycrystalline AlON. Various choices of initial resistances to slip, twinning, or shear fracture that result in similar predictions for average stresses in polycrystals but different predictions for defect densities (accumulated dislocations and twin volume fractions) are investigated. Predictions for single crystals provide insight into grain orientation effects not available from previous experimental investigations.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 3

Maximum shear stress for polycrystalline AlON in uniaxial strain: experiments (25) and predictions for slip/twin/fracture model parameters

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Figure 4

Average temperature for polycrystalline AlON in uniaxial strain: model predictions

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Figure 5

Predicted defect densities for polycrystalline AlON in uniaxial strain: (a) total twin volume fraction and (b) dislocation density

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Figure 6

Predicted (a) axial stress and (b) maximum shear stress for AlON in uniaxial strain: single crystals (various slip/twin models) and a fully dense polycrystal

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Figure 7

Predicted total twin volume fraction (curve not visible↔negligible values) (a) and dislocation density (b) for AlON in uniaxial strain: single crystals (various slip/twin models) and a fully dense polycrystal

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Figure 2

Axial stress for polycrystalline AlON in uniaxial strain: (a) experiments (24-27) and model predictions (equal slip and twin resistances) and (b) model predictions for various slip/twin/fracture parameters and elasticity models (upper four curves in (b) are nearly indistinguishable)

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Figure 1

Hydrostatic pressure for polycrystalline AlON: experiments (25) and model predictions

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