Anisotropic Dislocation Line Energy and Crack Tip Dislocation Nucleation in (alpha)RDX
Final rept. 2 Jun 2012
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD COMPUTATIONAL AND INFORMATION SCIENCES DIRECTORATE
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This work reports on the algorithms used to determine the anisotropic and isotropic elastic properties of dislocations and their nucleation from a crack tip. The appendix contains a numerical implementation of these algorithms in Matlab. The algorithms are demonstrated for the the energetic molecular crystal RDX, which has orthotropic elastic constants. The energy prefactor tensor is determined for several dislocation and crack tip configurations for RDX in order to calculate dislocation nucleation thresholds for different loading scenarios. Anisotropic results are compared to results obtained using isotropic material averages. The case of crack tip shielding due to partial dislocation nucleation is also presented. The anisotropic elastic results for the KII load factor required for dislocation nucleation are shown to compare well with recently published molecular dynamics simulations of this process.
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