Measuring the Strength of Metals by Extending the Richtmyer-Meshkov Instability to Shockless Loading

In this study we examine and compare two closely related approaches for quantifying the strength of metals at high strain-rates and relatively low pressures. In the first, specimens are patterned with sinusoidal perturbations on one surface, and impacted on the other by a projectile fired from a gas gun. The shock wave that propagates through the material achieves strain rates in excess of 10⁷ 1/sec and induces a Richtmyer-Meshkov Instability (RMI) that initiates an inversion of the sinusoidal pattern. The nature and extent of this inversion, and in particular its arrest (or perhaps lack thereof), reveals information about the material's strength. The second method is similar, but utilizes pulsed-power on Sandia's Thor platform to induce a shockless loading path that results in strain rates up to about 10⁶ 1/sec and produces a similar inversion of the patterned surface. This method can provide strength information in regimes between those explored by Hopkinson bar and traditional RMI. In this presentation we will provide an overview of RMI and its counterpart in the shockless loading regime, describe the use of simulations to quantify strength in loading conditions from gas-gun and Thor experiments on steel and tin, and discuss strategies for using simulations to meaningfully interpret measurements and infer strength.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc, for the US Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.