A hierarchical thermo-mechanical multi-scale technique for modeling of edge dislocations in nano-crystalline structures

M Jahanshahi and AR Khoei and N Heidarzadeh and N Jafarian, COMPUTATIONAL MATERIALS SCIENCE, 141, 360-374 (2018).

DOI: 10.1016/j.commatsci.2017.09.043

In this paper, a hierarchical multi-scale technique is developed to investigate the thermo-mechanical behavior of nano-crystalline structures in the presence of edge dislocations. The primary edge dislocations are generated by proper adjustment of atomic positions to resemble discrete dislocations. The interatomic potential used to perform atomistic simulation is based on the Finnis-Sinclair embedded- atom method as many-body potential and, the Nose-Hoover thermostat is employed to control the effect of temperature. The strain energy density function is obtained for various representative volume elements under biaxial and shear loadings by fitting a fourth order polynomial in the atomistic level. The material elastic constants are calculated by evaluating the second derivatives of the total potential energy per unit volume with respect to strain components. The evolutions of yield stress, elastic constants and bulk modulus are derived for nano-crystals of magnesium with hcp atomic structure containing different number of edge dislocations at various temperature levels. In order to provide a relation between various quantities in nano-scale level to their counterparts in macro-scale level, the material properties obtained from molecular dynamics simulations are transferred to the Gauss points of finite element mesh using the calculated strain energy function. The numerical results clearly demonstrate the behavior of material in the presence of edge dislocations at various temperatures. (C) 2017 Elsevier B.V. All rights reserved.

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