Orson L. Anderson
Ctr. for Earth and Planetary Sci., Inst. for Geophys. and Planetary Phys., UCLA, Los Angeles, CA 90024
It is no accident that resonant ultrasound spectroscopy (RUS) work is deeply connected to geophysics problems. A great triumph of geophysics in the past two decades has been the inversion of the measured resonant vibration modes of the oscillating Earth as a whole, resulting from a major earthquake, to find the density distribution with depth. Over the last 20 years the fundamental theory has been extended by a series of steps to include nonspherical shapes (parallelepipeds, cones, ellipsoids, and right circular cylinders) and also materials of lower symmetry (including cubic down to monoclinic). The advent of supercomputers with their large computation capacity has made all of this possible. The benefits of applying resonant ultrasound spectroscopy to geophysical problems are also benefits to materials science, since the geophysical approach is almost identical to a good materials science approach. In this paper, some results are presented of using RUS to find solutions to some outstanding geophysical problems mainly related to high temperature applications. The materials science applications of the work are found when one emphasizes measurements of insulators of low crystal symmetry at high temperatures (up to 1800 K). This is, of course, the special domain of high-temperature ceramics. A large portion of this paper is devoted to a historical review of RUS.