Novel Method of Measuring Elastic and Anelastic Properties of Solids

Abstract

A technique has been devised whereby the elastic and anelastic properties of solids can be measured both as a function of frequency and temperature. A small sphere, of the order of a few millimeters in diameter, is placed without bonding on a shear mode transducer. The transducer is driven with a pulse at one of the sphere's resonant frequencies and the free decay of the sphere's vibrations is observed by switching the transducer to a receiver. From the decay of the vibrations, the internal friction Q−1 may be calculated. Various modes may be excited and from comparison with the computed mode spectra of an isotropic solid, the Lamé constants, λ and μ, and Poisson's ratio may be calculated directly. Measurements have been made over a range of temperatures from 1.4 to near 400°K, the present upper limit being set by the solder connections to the transducer. Several materials have been tested and the results for two single-crystal nonmagnetic garnet spheres are given as representative of the capabilities of the technique for reasonably isotropic substances. The values of Q−1 for these garnets lie between 3×10−7 and 2×10−5 at a frequency of approximately 2 Mc.