Dislocation-based models of high-rate tantalum strength

We propose a new model of tantalum strength, which is suitable for quasistatic to high-rate loading conditions.  The model is calibrated to experiments at low to intermediate strain rates (<10⁵/s) and atomistic data at higher rates (~10⁵ to 10⁸/s).  Here, we investigate mechanisms of dislocation generation that may explain the observed upturn in saturation dislocation density and flow stress at rates above ~10⁵/s.  The mechanisms considered are (i) dislocation self-multiplication from cross-kink interactions, and (ii) line length production from dislocation avalanches.  While models of both mechanisms fit the data reasonably well, dislocation self-multiplication in a dense network seems unlikely.  The model is exercised in hydrocode simulations of Richtmyer-Meshkov instability experiments to assess model predictions of high-rate tantalum strength.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 (LLNL-ABS-844654).