Steady-wave risetime and spall measurements on uranium (3-15 GPA)
Planar impact experiments using thin discs of z-cut crystalline sapphire as impactors on samples of unalloyed uranium (D-38) have been performed over the pressure range of elastic response of the sapphire. The time-resolved motion of the uranium back free surface, due to the emerging shock wave, was monitored with laser velocity interferometry (VISAR). The propagation distance in most of the tests was sufficient to achieve a steady-wave plastic shock, and fast sweeping oscilloscopes were focused strictly on the rapidly-rising plastic wave. Impactor and sample thicknesses were selected to achieve spall within the uranium, and the spall signals were also measured. Risetime measurements indicate that the maximum strain rate in the plastic shock wave increases with the Hugoniot pressure, tending to a fourth power dependence at higher amplitudes, consistent with similar measurements on other metals. The spall strength determined from the pull-back signal ranges from 2.6 to 3.3 GPa and increases with increasing shock amplitude. Magnitude and rate dependence of the latter are consistent with a prediction of spall strength based on the material fracture toughness.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5426090
- Report Number(s):
- SAND-85-0233C; CONF-850889-3; ON: DE85015163
- Country of Publication:
- United States
- Language:
- English
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