When a metal is subjected to a ‘weak’ shock a longitudinal elastic wave propagates into the metal activating mechanisms of plastic relaxation such as dislocation motion and twinning in its wake. Traditional methods of dislocation dynamics treat the elastic fields of dislocations quasi-statically. That is to say the explicit time dependence of the elastic fields is ignored; the force acting on a dislocation segment is calculated by evaluating the static stress fields of other dislocation segments in positions they occupy at a given instant in time.
We have shown that when this approach is applied to shock loading it violates causality: dislocations are activated ahead of the shock front. To avoid this nonsense it is essential to treat explicitly the time dependence of the elastic fields associated with the creation and movement of dislocations. Building on the pioneering work of Markenscoff and Clifton  we showed in  how this can be done in 2D-simulations of the plastic relaxation of elastic shocks by the creation and movement of edge dislocations: Dynamic Discrete Dislocation Plasticity (D3P). In this talk I will outline what is involved in the fully time-dependent approach of D3P. I will also present recent unpublished results on the application of D3P to the decay of the elastic precursor in aluminum.
This research was carried out in the Centre for Doctoral Training in Theory and Simulation of Materials at Imperial College London, which is funded by the EPSRC under grant no. EP/G036888/1.
B.G.-L. acknowledges the support of the Department of Universities and Education of the Basque Government.
1. “The nonuniformly moving edge dislocation”, X Markenscoff and R J Clifton, J. Mech. Phys.Solids vol 29, 253-262 (1981).
2. “A dynamic discrete dislocation plasticity method for the simulation of plastic relaxation under shock loading”, B Gurrutxaga-Lerma, D S Balint, D Dini, D E Eakins, A P Sutton, Proc. R. Soc. A vol 469, 20130141 (2013).