Modeling High Strain Rate Plasticity in BCC Lead

We report on the strength (flow stress) of lead at high pressure and high strain rate. We focus on the high-pressure body-centered cubic (bcc) phase of lead. There are two models of lead strength at high strain rate that have been available previously. Both models were constructed using data from the low-pressure, face-centered cubic phase of lead. Plasticity in bcc and fcc crystals can be very different. Recent experiments conducted at the National Ignition Facility have used ramp-compression to drive Rayleigh-Taylor instability and have measured the ripple growth to infer lead strength at high pressure. Those experiments are dominated by behavior in the bcc phase. We have developed an Improved Steinberg-Guinan model for bcc lead strength [1] using ab initio calculations of the shear modulus at pressure, as well as hardening parameters from other bcc metals. We compare the predictions of the new model with those from the two previous models and preliminary results from the experiments.
[1] Robert E. Rudd et al., APS SCCM Proceedings, 2017.