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The evolution of elastic-plastic shock waves with the propagation distance has been studied in 99.99% purity aluminum and in annealed 6061 aluminum alloy. The free surface velocity histories of shock-loaded samples, 0.1–2.0 mm thick and with initial temperature from 296 to 932 K, have been recorded using velocity interferometer system for any reflector (VISAR). The measured amplitudes of the elastic precursor waves have been approximated by power functions of the propagation distance, and these data have been converted into relationships between the shear stress at the top of elastic precursor wave and the initial plastic strain rate. The latter was found to decrease from 106 to 104 s−1 over 0.1 to 2-mm precursor traverse, while the density of mobile dislocations corresponding to these strain rates varied from 2 × 108 to 5 × 106 cm−2. At fixed strain rates, the flow stress of aluminum grows linearly with temperature. An analysis of the rise times of the plastic shock waves has shown that, for the same level of shear stress, the plastic strain rate at the shock front is by an order of magnitude higher and the density of mobile dislocations is 2-3 times higher than their initial values behind the elastic precursor front.

An experimental facility was developed to obtain real-time, quantitative, x-ray diffraction data in laboratory plate impact experiments. A powder gun, to generate plane wave loading in samples, was designed and built specifically to permit flash x-ray diffraction measurements in shock-compression experiments. Spatial resolution and quality of the diffracted signals were improved significantly over past attempts through partial collimation of the incident beam and the use of two-dimensional detectors to record data from shocked crystals. The experimental configuration and synchronization issues are discussed, and relevant details of the x-ray system and the powder gun are described. Representative results are presented from experiments designed to determine unit cell compression in shock-compressed LiF single crystals subjected to both elastic and elastic-plastic deformation, respectively. The developments described here are expected to be useful for examining lattice deformation and structural changes in shock wave compression studies.

Effect of temperature, strain, and strain rate on the flow stress of aluminum under shock-wave compression J. Appl. Phys. 112, 073504 (2012); 10.1063/1.4755792 Modeling of the elastic precursor behavior and dynamic inelasticity of tantalum under ramp wave loading to 17 GPa J. Appl. Phys. 107, 083508 (2010); 10.1063/1.3373388 Large elastic wave amplitude and attenuation in shocked pure aluminumThe evolution of the elastic precursor waves in pure tantalum and vanadium is presented at normal and elevated temperatures over propagation distances that ranged from 0.125 to 3 mm. Measurements were performed in order to obtain experimental data about the temperature-rate dependence of the yield stress of the two metals. With increasing propagation distance, the rate of the decay of elastic precursor decreases, as the shear stress in the elastic precursor wave approaches the Peierls stresses. It has been found that the decay, with propagation distance, of the post-spike minimum of the spike-like elastic precursor wave in vanadium is essentially non-monotonous. The experiments also revealed that annealing of tantalum and vanadium increases their Hugoniot elastic limit. The anomalous increase of the high strain rate yield stress with temperature, as observed earlier for some FCC and HCP metals, has not been detected in these measurements. V C 2014 AIP Publishing LLC. [http://dx.

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