The dynamic strength behavior of bcc metals is intimately related to underlying dislocation microstructure, which can evolve substantially under extreme loading conditions. In this work, we propose a new model of dislocation network evolution for tantalum, based on two internal state variables: the dislocation density and the network average link length. The network model is incorporated in a multiscale strength model, which addresses thermally-activated kink-pair nucleation at lower stresses and drag-limited slip at higher stresses. The model has been calibrated against large-scale atomistic simulations that involve strain rates of 10^5 to 10^8/s, temperatures of 100 to 1000 K, and compressive strains of ~140%. Ongoing work focuses on calibrating the model to experimental measurements at quasi-static and intermediate rates and the simulation of integrated measurements for assessments of material 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-797785).