Estimation of Metal Strength at Very High Rates Using Free-Surface Richtmyer–Meshkov Instabilities

Tantalum strength at extreme strain rates from impact-driven Richtmyer-Meshkov instabilities

“…This work builds and improves upon previous efforts that also capitalized on the more experimentally accessible freesurface (Atwood number = -1) RMI configuration to quantitatively estimate strength at low pressure and rates up to at least 10 7 /s [19][20][21][22]. The previous efforts used high explosive loading to generate the shock.…”

“…In our more limiting case with perturbations on the free surface, local interactions of release waves from the perturbed surface eventually result in tensile stresses leading to damage in the form of porosity for a ductile metal [38,39]. In previous work, it was demonstrated that the peak spike velocity occurred early enough to be unaffected by porosity, and it still has excellent sensitivity to strength; hence it makes an ideal metric [22]. Soon after the peak and well before the spike has arrested, the porosity grows enough to affect the total spike growth and compromise a strength estimate based on this total growth.…”

“…To estimate strength, this work uses the peak spike velocity, v s max , as the experimental metric to compare with the model [22]. By contrast, the originally proposed method to quantitatively estimate strength used the total integrated spike growth as the experimental metric, but that method was based on calculations for a general RMI configuration with a perturbed interface between two materials [18].…”

“…The sensitivity of RMI to strength in solids, the analog of viscosity, has received explicit attention more recently [6][7][8][9][10][11][12] with increasing attention also in regard to ejecta [13][14][15][16]. Since the proposal about a decade ago to use RMI to evaluate strength [17,18], several experimental efforts to use this capability have been reported [19][20][21][22][23][24][25][26][27][28][29], although in many cases the experiments serve as validation experiments for strength models rather than providing quantitative estimates of strength.…”

“…Estimating strength from RMI data requires modeling the experiments in a hydrocode or something similar. Impact loading can be modeled both more simply and more accurately than high explosive loading, as illustrated by the significant previous effort to model explosive loading [22]. More accurate modeling should lead to easier and more accurate strength estimation.…”