Finite-temperature non-equilibrium quasi-continuum analysis of nanovoid growth in copper at low and high strain rates
We study dynamic nanovoid growth in copper single crystals under prescribed volumetric strain rates ranging from moderate (∊̇=10^5 s^(-1)) to high (∊̇=10^(10)s^(-1)). We gain access to lower strain rates by accounting for thermal vibrations in an entropic sense within the framework of maximum-entropy non-equilibrium statistical mechanics. We additionally account for heat conduction by means of empirical atomic-level kinetic laws. The resulting mean trajectories of the atoms are smooth and can be integrated implicitly using large time steps, greatly in excess of those required by molecular dynamics. We also gain access to large computational cells by means of spatial coarse-graining using the quasicontinuum method. On this basis, we identify a transition, somewhere between 10^7 and 10^8 s^(−1), between two regimes: a quasistatic regime characterized by nearly isothermal behavior and low dislocation velocities; and a dynamic regime characterized by nearly adiabatic conditions and high dislocation velocities. We also elucidate the precise mechanisms underlying dislocation emission from the nanovoids during cavitation. We additionally investigate the sensitivity of the results of the analysis to the choice of interatomic potential by comparing two EAM-type potentials.
© 2015 Elsevier Ltd. Received 14 August 2014; Received in revised form 14 January 2015; Available online 7 March 2015. We gratefully acknowledge the support of the Ministerio de Ciencia e Innovación of Spain (DPI2009-14305-C02-01 and DPI2012-32508) and from the U. S. Army Research Laboratory (ARL) through the Materials in Extreme Dynamic Environments (MEDE) Collaborative Research Alliance (CRA) under Award Number W911NF-11-R-0001. P.A. and M.O. gratefully acknowledge support from the Department of Energy National Nuclear Security Administration under Award Number DE-FC52-08NA28613 through Caltech's ASC/PSAAP Center for the Predictive Modeling and Simulation of High Energy Density Dynamic Response of Materials.