Magnetic loading technique. (a) Schematic of the experiment configuration showing where planar magnetic field is produced between flat panels of 1100 Al or OFHC Cu panels. (b) Input current-time history (I) and input magnetic pressure history (P) to the drive panels used for Veloce experiments. The zero-to-peak rise time of the pressure drive is approximately 450 ns.
Particle velocity wave profile obtained on expt. V-224, illustrating features important to the interpretation of dynamic material response.
Typical single- and double-sample measurements on annealed Ta. (a) Single sample results from expt. V-180 for sample thickness of 1.898 mm. The upper (red) curves are the measured profiles at the Al/LiF and Ta/LiF interfaces. The lower (black) curves are the converted input and output in situ profiles. (b) Double sample measurement from expt. V-168 for sample thicknesses of 1.507 and 2.362 mm. The upper (red) and lower (black) curves are measured and in situ profiles, respectively.
Experimental in situ particle velocity and strain rate profiles obtained for annealed Ta; (a) from expt. V-198 and (b) from expt. V-203.
In situ particle velocity profiles for annealed and cold-rolled Ta; (a) from expts. V-224, V-225, V-226, and V-227 on annealed Ta; (b) from expts. V-228, V-245, and V-247 on cold-rolled Ta. is the wave velocity for loading and is the wave velocity for unloading.
Attenuation of the peak in situ particle velocity as a function of propagation distance.
Elastic yield strength obtained on annealed and cold-rolled Ta as a function of propagation distance. (a) Quasiisentropic elastic yield stress for two impurity levels of annealed Ta and for cold-rolled Ta. (b) is the yield strength corresponding to initial yielding and is the yield stress after stress relaxation but prior to arrival of the plastic wave.
Lagrangian wave velocity as a function of in situ particle velocity; (a) data from expts. V-228, V-245, and V-247 on cold-rolled Ta and comparison with theoretical calculations (Ref. 69) of the bulk and longitudinal Lagrangian velocities assuming a constant Poisson’s ratio; (b) from expts. V-168, V-198, and V-203 on annealed Ta.
Technique for estimating flow strength during QE unloading from peak loading stresses (a) Conceptual stress-strain response for EPP response during uniaxial strain loading. The unloading response of metals deviates from this, as represented by the curve labeled QE. At lower strains, unloading is governed by the plastic response. (b) Lagrangian wave velocity vs particle velocity corresponding to the stress-strain curves in (a). The change in particle velocity across the QE transition region is used to estimate the flow strength at peak stress. The term corrects for the drop in particle velocity from the peak input particle velocity.
(a) Flow strength of annealed and cold-rolled Ta as a function of peak stress, and comparison with the Steinberg (Refs. 57–60) and MTS (Ref. 10) strength models. The QE plastic strain rate during unloading ranged from . (b) Initial flow strength of annealed Ta as a function of plastic strain rate, and comparison with predictions of the MTS model (Ref. 70).
Comparison with the flow strength for cold-rolled Ta as determined from the stress offset between the compressive loading curve and hydrostatic predictions; from the MTS model prediction for compressive loading, and from the measured QE unloading profiles. (a) Measured stress-strain response for cold-rolled Ta (expt. V-228) and comparison with the isentrope calculated by Greef et al. (Ref. 69). (b) Flow stress of cold-rolled Ta vs longitudinal stress with comparison to a MTS model prediction for the expected plastic strain rate during compression and the estimated flow strength determined from the QE unloading response. The QE measurements have been corrected using Eq. (11) to account for the difference in plastic strain rate for QE unloading vs compressive loading.
QE strain in annealed and cold-rolled Ta vs peak longitudinal stress.
Initial yield response.
Flow strength parameters.
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