Center for Advanced Vehicular Systems

Spotlight on Research - A Multi-Scale Framework of the Plasticity: Method and Validation

A numerical and hierarchical multi-scale framework of plasticity for metals with a low Peierls stress (FCC metals) has been developed. The framework (see Figure) uses Molecular Dynamics (MD) and Discrete Dislocations (DD) to compute the material parameters of the hardening law used in a dislocation-based Crystal Plasticity Model (CPM). The drag coefficient, which captures the interactions between the dislocations and the phonons, is extracted from calculations at the lowest length scale (see Figure A) and then transferred hierarchically to the DD level, (see Figure B). With this information, DD is then used to simulate the evolution of plasticity, which results from the interaction of a large population of dislocations. Next, the material parameters embedded in the hardening law of the CPM (see Figure C) are computed using a fitting procedure based on both the functional form of the hardening law and the internal elastic stress / plastic shear strain fields computed from DD.

Such a bridging methodology has been validated by using the multi-scale crystal plasticity model to predict the mechanical response of an Al single crystal deformed under uniaxial compressive loading. The computed strain-stress response agrees well with the experimental data (see Figures).