Using one-dimensional strain conditions, the dynamic stress-wave response of polycrystalline Al2O3 was measured with interferometry in both stress-wave loading and unloading to about 16 GPa and with slanted resistor gauges in loading to about 50 GPa. The stress-wave loading and unloading measurements were of high resolution and showed a 9.1-GPa elastic precursor wave (velocity 10.9 km/s) followed by a slower dispersive permanent deformation wave. Unloading was elastic in the stress range of these experiments. Both loading and unloading wave propagation were modeled well with a Maxwellian elastic-stress-relaxing model with a yield stress of 5.8 GPa and a relaxation time of 70 ns. The rate-dependent model correctly predicts both the dispersion of the permanent deformation wave and the unloading-wave behavior. The bulk pressure-volume behavior of alumina is given by the shock-velocity–particle-velocity relationship of Us=8.14 +1.28up (km/s). Thermodynamic corrections to the dynamic bulk response yielded isothermal pressure-volume results which agreed well with direct hydrostatic determinations on polycrystalline Al2O3 and with results deduced from ultrasonic determinations on Lucalox. Permanent deformation of Al2O3 from a micromechanical standpoint appeared to be compatible with a model involving general microcracking throughout the volume of the material. This model is supported by the lack of an appreciable spall strength. When the yield process is ascribed to the onset of microfracture, which depends upon the initial flaw size and distribution, the earlier results on single crystals are phenomenologically related to the stress-wave behavior observed during this study on polycrystalline alumina.

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X-ray momentum coupling coefficients, CM, were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the Sandia National Laboratories Z-machine. Velocity interferometry (VISAR) diagnostics provided equation-of-state data. Targets were iron and stone meteorites, magnesium-rich olivine (dunite) solid and powder (~5–300 μm), and Si, Al, and Fe calibration targets. Samples were ~1-mm thick and, except for Si, backed by LiF single-crystal windows. X-ray spectra combined thermal radiation (blackbody 170–237 eV) and line emissions from pinch materials (Cu, Ni, Al, or stainless steel). Target fluences of 0.4–1.7 kJ/cm2 at intensities of 43–260GW/cm2 produced plasma pressures of 2.6–12.4 GPa. The short (~5 ns) drive pulses gave rise to attenuating stress waves in the samples. The attenuating wave impulse is constant, allowing accurate CM measurements from rear-surface motion. CM was 1.9 − 3.1 × 10−5 s/m for stony meteorites, 2.7 and 0.5 × 10−5 s/m for solid and powdered dunite, 0.8 − 1.4 × 10−5 s/m for iron meteorites, and 0.3, 1.8, and 2.7 × 10−5 s/m respectively for Si, Fe, and Al calibration targets. Results are consistent with geometric scaling from recent laser hohlraum measurements. CTH hydrocode modeling of X-ray coupling to porous silica corroborated experimental measurements and supported extrapolations to other materials. CTH-modeled CM for porous materials was low and consistent with experimental results. Analytic modeling (BBAY) of X-ray radiation-induced momentum coupling to selected materials was also performed, often producing higher CM values than experimental results. Reasons for the higher values include neglect of solid ejecta mechanisms, turbulent mixing of heterogeneous phases, variances in heats of melt/vaporization, sample inhomogeneities, wave interactions at the sample/window boundary, and finite sample/window sizes. The measurements validate application of CM to (inhomogeneous) planetary materials from high-intensity soft X-ray radiation.

WoPJDp V solves the finite difference analogs t o the Lagrangian equations of motion i n one spatial dimension (planar, cylindrical, or sphericall-Simulations of explosive detonation, energy deposition, p l a t e impact, and dynamic fracture are possible, using a variety of existing material models-In addition, WONDY has proven t o he a powerful t o o l i n the evaluation of new constitutive models-A preprocessor is available t o allocate storage arrays commensurate with problem size, and automatic rezoning may be employed t o improve resolution. solved, available material models, operating instructions, and sample problems. T h i s docuppent provides a description of the equations coIITL#Ts

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A model that predicts the final velocity of high-power, pulsed-laser-driven thin flyers is described. The required input parameters can either be obtained from standard handbooks or simply extracted from one set of data. The model yields a number of features and scaling laws that are well verified by experiment. Specific comparisons of model predictions with experimental results illustrate excellent agreement for variations of laser fluence and pulse width as well as flyer diameter and thickness

Abstract. High-energy pulsed X-ray momentum coupling is a promising technology for early deflection of NEOs (Near Earth Objects) that might impact Earth. Analytic models for the radiation interactions can often preclude the need for large hydrocode analyses, and offer the advantage of many simple calculations that reveal important features of the nonlinear phenomena, e.g., thresholds, peak coupling, and high-energy scaling limits. However, model validation is an important element. One such model is used to analyze relevant experiments conducted on the Sandia Z-pinch machine. Samples were exposed to X-ray pulses approximating a 200-eV blackbody at fluences of ~1 kJ/cm 2 . Target momenta were measured. Model calculations give impulse couplings somewhat greater than the data, but a more appropriate value for the one uncertain model parameter (the effective target decomposition energy), can account for this discrepancy. The analytic model is thus appropriate for system-level parameter studies that will be important constituents of all NEO mitigation investigations.