Elastic properties of metals and minerals under shock compression

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6658012

Duffy, T S

Comparison of laboratory elasticity data with seismic measurements of the Earth provides a means to understand the deep interior. In this work, elastic wave velocities have been measured under shock compression to 80 GPa in an Fe-Cr-Ni alloy, to 27 GPa in polycrystalline MgO, and to 81 GPa in molybdenum preheated to 1400[degrees]C. These measurements were made by recording particle velocity histories at a sample surface using the method of velocity interferometry. Compressional and bulk wave velocities in Fe-Cr-Ni alloy are consistent with third-order finite strain theory and ultrasonic data. The measured wave profiles can be successfully reproduced by numerical simulations utilizing elastic-plastic theory modified by a Bauschinger effect and stress relaxation. Material strength was found to increase by a factor of at least 5 up to 80 GPa and to be 2-3% of the total stress. Compressional and bulk velocities in Fe-Cr-Ni define linear velocity-density trends and can be modeled by averaging properties of Fe, Cr, and Ni. The effect of alloying [approximately]4 wt.% Ni with Fe would change both V[sub P] and V[sub B] by less than 1% under Earth's core conditions. Compressional and shear velocities in Fe-Ni are compatible with inner core values when corrected for thermal effects. Wave profile and EOS measurements in polycrystalline MgO define its EOS: U[sub S] = 6.77(0.08) + 1.27(0.04)[mu][sub p]. Compressional sound velocities to 27 GPa yield a longitudinal modulus and its pressure derivative which are in good agreement with ultrasonic determinations. The unloading wave profiles can be modeled using a modified elastic-plastic constitutive response originally developed for metals. Thermal expansivities in MgO have been determined to be 12 [+-] 14 [times] 10[sup [minus]6] K[sup [minus]1] at P = 174-200 GPa and T = 3100-3600 K from shock temperature and EOS data. These results imply that the Earth's lower mantle is enriched in Si and/or Fe relative to the upper mantle.

• Research Organization: California Inst. of Tech., Pasadena, CA (United States)
• OSTI ID: 6658012
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
360203 -- Ceramics
Cermets
& Refractories-- Mechanical Properties
58 GEOSCIENCES
580000 -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
CHALCOGENIDES
CHROMIUM ALLOYS
COMPRESSION
EARTH PLANET
ELASTICITY
ELEMENTS
IRON ALLOYS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MECHANICAL PROPERTIES
METALS
MINERALS
NICKEL ALLOYS
OXIDES
OXYGEN COMPOUNDS
PLANETS
TENSILE PROPERTIES