Multiscale Modeling of Deformation Twinning Based on Field Theory of Multiscale Plasticity (FTMP)
Final rept. Oct 2012-Jun 2013
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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In this report, we discuss the application of a field theory, incorporating first and second gradients of plastic distortion into the constitutive response of metallic single crystals. Differential-geometric aspects of the theory are briefly summarized, and a constitutive model for ductile crystals is then outlined. We also report simulations that confirm basic capabilities of the model in terms of describing important features of deformation twinning, e.g., nucleation, growth, lattice rotation, and the attendant stress response and energy redistribution. Using numerical results for face-centered cubic metals single crystals and polycrystalline samples of copper we examine the effects of geometrical constraints. Numerical results for hexagonal close-packed metals specifically, magnesium single crystals demonstrate interactions between twinning and slip, tension-compression asymmetry, reversibility, and other typically observed properties. Agreement with experiments is satisfactory.