The dynamic strength responses of bcc metals are 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, which is based on two internal state variables: the dislocation density and the network average link length. The network model is exercised in the framework of 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 106 to 108 s-1, temperatures of 100 to 1000 K, and compressive strains of ~140%. Ongoing work focuses on comparing 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).