Atomistic simulation studies of size effects in plasticity: Compression of single- and polydomain crystals in two dimensions

摘要

We perform atomistic Monte Carlo simulations of a Lennard-Jones crystal under uniaxial compression on single crystal and polycrystalline samples in two dimensions. In single crystals, we observe a size effect in initial yield: Smaller samples yield at higher stress. We also find a size effect in the plastic regime which is accounted for by dislocation starvation. Two-dimensional polycrystalline samples are generated using a statistical physics model, and studied under uniaxial compression. The resulting microstructures showhigher stress within the grain boundary regions relative to that in the bulk, consistent with theoretical models and experimental results. We also examine the broad istribution of stresses within the polydomain sample and compare with recent experimental observations. While 2D simulations cannot predict behaviorof real 3D solids, they are valuable for exploring some of the fundamental mechanisms controlling mechanical response and serve as a testing ground for theories of size effects in plasticity.