Atomic plasticity: description and analysis of a one-billion atom simulation of ductile materials failure

摘要

Large scale atomic simulations are becoming an increasingly important tool in modeling deformation and failure mechanisms of materials. Here we describe and analyze a recent one-billion-atom simulation of ductile materials failure [PNAS 99 (9) (2002) 5783] where the complexity of creation and collective behavior of thousands of dislocations are revealed, for the first time, from atomic to submicron length scales. The amount of information that can be extracted from such large-scale simulations is truly overwhelming, and graphic visualization of dynamic dislocation motion and interactions are breathtaking. We present some of our preliminary analysis of the one-billion-atom simulation which indicates several interesting and unique features characterizing interactions among a large number of dislocations. A sessile defect structure is observed to develop on the time scale of several picoseconds, effectively locking further dislocation motion and causing the material to work harden. We make analysis of the activated slip systems, the dislocation reactions leading to rigid junctions and the formation of sessile defect structure. In order to render the present study more comprehensive to the readers from a continuum plasticity background and stimulate further interests in this area of research, we also include some brief reviews of some of the previous studies as well as commonly used simulation, visualization and analysis techniques on atomistic modeling of dislocation plasticity. Finally, we discuss possible ways to link continuum mechanics theories of plasticity with atomistic simulation results via the dislocation density tensor.