Kadkhodapour - Mech. Eng. Department Isfahan Univ. of Tech.
Ziaei-Rad - Mech. Eng. Department. Isfahan Univ. of Tech.
Karim zadeh - Mat. Eng. Department Isfahan Univ. of Tech.
Hassanpour - Mech. Eng. Department Isfahan Univ. of Tech.

Inspired by recent molecular dynamic simulations of nanocrystalline solids, a generalized self-consistent polycrystal model is proposed to study the mechanical properties of polycrystalline metals as the grain size decreases from the traditional coarse grain to the nanometer scale. These atomic simulations revealed that a significant portion of atoms resides in the grain boundaries and the plastic flow of the grain-boundary region is responsible for the unique characteristics displayed by such materials. The proposed model takes each oriented grain and its immediate grain boundary to form a pair. And then making use of a composite model, the nonlinear behavior of the nanocrystalline polycrystal is determined. The finite element method is employed in conjunction with a unit cell of the composite to investigate the compressive and tensile behavior of the system. An empirical elasto-plastic relation is used to describe the plastic flow behaviour of the matrix while grain size effects are included by the classic Hall–Petch relation. The boundary phase is assumed to have the mechanical properties of a quasi-amorphous material. The results of the calculations are compared with previously published experimental data. The agreement between results indicates the suitability of the model for nanocrystalline materials.

Nanocrystalline materials; finite element; composite model