Recent progress in dislocation dynamics
Sylvie Aubry (LLNL), Athanasios Arsenlis (LLNL)
Materials for Extreme Environments: Multiscale Experiments and Simulations
Mon 9:00 - 10:30
Salomon 203
The dislocation dynamics (DD) method models dislocations behavior, interactions and evolution in BCC and FCC materials. It is used to predict the strength of a material that varies with pressure, strain rate, temperature and evolving dislocation density by providing input parameters to continuum based approaches. Continuum models based on constitutive equations built using dislocation dynamics and molecular dynamics data have been successfully compared to high energy physics experiments in BCC tantalum and vanadium. We are constructing a new model to evaluate the strength of Beryllium and Magnesium which are hexagonal closed packed (HCP) materials. It involves the implementation of a more complex set of Burgers vectors and planes to account for the HCP lattice as well as new topological operations particular to HCP materials. Large scale dislocation dynamics simulations usually involve several millions of interacting dislocation segments. The stress at a point and interaction force between two segments need to be computed many times during simulations. Up to now, DD simulations were restricted to isotropic elasticity calculations because using anisotropic elasticity was perceived as too expensive. We evaluate the cost versus accuracy of using spherical harmonics series to approximate the anisotropic elastic Green's function in calculating stresses and forces between segments. The stress at a point is obtained by analytically integrating the spherical harmonics series once and the forces by integrating it analytically twice. We analyze the convergence and cost of using this approach and describe the elements of a fast implementation. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.