Atomistic simulations of spall in metals
Abstract
Molecular-dynamics (MD) simulations (up to 10^8 atoms) of shocks in embedded atom method Cu will be presented. A `piston' was moved with a given velocity profile (square pulse or linear ramp) to produce a shock, and it was stopped when the shock reached the back of the sample, leading to two release waves meeting at the middle of the sample. Above a critical shock pressure a spall plane was formed. Runs for both perfect crystals and crystals with defects will be shown. Shock-induced dislocation densities are diminished by the rarefaction wave and pre-existing defects can affect void nucleation. Due to the relatively small length of our samples (up to 0.3 microns) multiple reflections play an important role in the final state of the sample and could be relevant for thin samples as the ones sometimes used in laser shocks. In addition, we will present void size versus time and pressure for MD simulations of both shocks and laser ablation. In the later case, temperatures close to melting facilitate void nucleation, leading to a nucleation threshold much lower than the threshold for pure shocks. The work at LLNL was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARB28010B