Flow strength of tantalum under ramp compression to 250 GPa

Abstract

Compressibility and strength of nanocrystalline tungsten boride under compression to 60GPaStrength and elastic moduli of TiN from radial x-ray diffraction under nonhydrostatic compression up to 45 GPa Modeling of the elastic precursor behavior and dynamic inelasticity of tantalum under ramp wave loading to 17 GPa A magnetic loading technique was used to study the strength of polycrystalline tantalum ramp compressed to peak stresses between 60 and 250 GPa. Velocimetry was used to monitor the planar ramp compression and release of various tantalum samples. A wave profile analysis was then employed to determine the pressure-dependence of the average shear stress upon unloading at strain rates on the order of 10 5 s À1 . Experimental uncertainties were quantified using a Monte Carlo approach, where values of 5% in the estimated pressure and 9-17% in the shear stress were calculated. The measured deviatoric response was found to be in good agreement with existing lower pressure strength data as well as several strength models. Significant deviations between the experiments and models, however, were observed at higher pressures where shear stresses of up to 5 GPa were measured. Additionally, these data suggest a significant effect of the initial material processing on the high pressure strength. Heavily worked or sputtered samples were found to support up to a 30% higher shear stress upon release than an annealed material. V C 2014 AIP Publishing LLC.

Estimating Material Properties Under Extreme Conditions by Using Bayesian Model Calibration with Functional Outputs

“…As a proof of principle, we re‐examine previously published measurements on tantalum (Ta) generated with pulsed magnetic fields (Brown et al ., ), accounting for previously ignored sources of uncertainty. Because these experiments have been analysed by using traditional analytic techniques, we can compare the computational simulation approach with the analytic technique to test whether the new approach results in similar inferences as well as quantify the effect of accounting for previously ignored sources of uncertainty.…”

“… Experimental measurements considered in this study and reported previously by Brown et al . (); each colour represents a different experiment…”

Molecular scale study of the plastic response of tantalum under ramp compression and release

“…The SC and NC Ta systems were found to have an initial average dislocation density of 2.35×10 16 m −2 and 1.49×10 16 m −2 respectively. These dislocation densities, while much higher than the expected dislocation densities in the high pressure experimental Ta samples [1,3], are within an order of magnitude of experimental measurements for heavily cold-worked polycrystalline and nanocrystalline metals [14,15]. FIGURE 2.…”

“…Recently, Brown et al [1] obtained strength values for tantalum (Ta) at 250 GPa and an average strain-rate of 3 × 10 5 s 1 during quasi-isentropic compression experiments that were well above previously accepted models, and demonstrated that changes in the initial microstructure resulted in changes in strength. The self-consistent Lagrangian analysis technique used by Brown et al [1] to extract strength was validated by Moore et al [2] using molecular dynamics (MD) techniques and provides credence to the finding that the dynamic strength is influenced by initial microstructure. However, Park et al [3] found Ta strength at 130 GPa and an average strain-rate of 1 × 10 7 s 1 to be independent of grain size during Rayleigh-Taylor instability growth experiments.…”

Application backwards characteristics analysis method to dynamic response of metals under high pressure

“…have attracted much attention because of interesting phenomena and great challenges to experiment and simulation. A number of experiments have shown that the dynamic yield strength of metals depends on loading pressure and rates very sensitively [1][2][3]. Techniques for strength measurement at high pressures include comparison to hydrostatic response, lateral stress gauges, growth of Rayleigh-Taylor instabilities [4,5], etc..…”