The measurement of the bulk modulus loss factor of small solid specimens

The bulk modulus loss factor of small, relatively loss-free solid specimens is one of the more elusive elastic constants to measure, as it is essential that the losses in the apparatus be reduced below those in the sample. A procedure described by Tamm in 1942. involves the insertion of the sample at a pressure maximum in a column of liquid resonating in a longitudinal mode; the loss factor was determined from the change in damping of this resonance. Essentially the same procedure was followed by Niemic in 1972, who reports a Q of 1300 as typical for the resonator without a sample. Simon in 1965 attempted to eliminate viscous loss in the boundary layer at the tube wall by the use of purely radial modes in spherical vessels such as have commonly been used for the measurement of the attenuation in liquids. He suspended the flask in a vacuum jacket to reduce radiation loading, and used a common transducer at the centre for the initial drive and the measurement of decay. He obtained a Q of over 20000, though the excitation of wall resonances and the asymmetry at the neck caused considerable difficulty. The present method makes use of a cylindrical vessel in order to produce a more practical system. [Continues.]