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Measurement of the Pressure Derivatives of Elastic Constants using Resonance Ultrasound Spectroscopy.

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Progress rept. 1 Mar 94-28 Feb 95,

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In our last years proposal to the Physical Acoustics Section of the Physics Division of ONR, we outlined an overall goal for three years and a goal for the first years work. The overall goal was to measure the third order elastic constants of non-isotropic solids. The first years goal was to prove out the measuring system and complete the measurements of third order constants on one solid, which will probably be KCl. We also promised to design the equipment to measure the remaining third order constants, not found from the hydrostatic pressure experiment. The measurement of resonant frequencies under hydrostatic pressure imposes some severe restraints on the measuring apparatus. Restraints arise because pressure will tend to damp the resonant modes, and if sufficient pressure exists, the observed modes will disappear in the noise of the system. We are obliged, therefore, to do the measurements at modest pressure 100-200 bars, which requires that the pressure measuring apparatus be very accurate. We chose the ultimate in accuracy for pressure-generating equipment, the dead weight loader. As a consequence, we had to design and order some specialized equipment. The equipment was purchased early, but when it first arrived it had to be returned to the manufacturer for modification. Our final system arrived considerably behind schedule, which frustrated our attempt to prove our measuring system early in the year. We have just completed the first few runs on our system, and have proved out the essential parts of the system. But this delay has prevented us from completing the measurement of third order constants on any solid. We are about to undertake these measurements at the beginning of the second year.

Subject Categories:

  • Acoustics
  • Fluid Mechanics

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