Mode identified resonant ultrasound spectroscopy.

Abstract

Resonant ultrasound spectroscopy (RUS) is a powerful tool for determining all independent elastic constants (Cij) of solids. Successful inverse calculation for Cij requires mode identification for measured resonance frequencies. In this lecture, two mode‐identified RUS methods developed by the author are presented. One is the electromagnetic acoustic resonance (EMAR) [Ogi et al., J. Acoust. Soc. Am. 106, 660 (1999)]. Using a solenoid coil and static magnetic field, vibrations of a specimen are measured through the electromagnetic‐force mechanisms. Detectable vibrational modes are controlled by changing the magnetic‐field direction. Because of the noncontacting measurement, it is applied to measurements at high temperatures easily. The second method incorporates the laser‐Doppler interferometry into RUS (RUS‐LDI method) [Ogi et al., J. Acoust. Soc. Am. 112, 2553 (2002)]. The specimen is set on the needle piezoelectric tripod in vacuum, and its displacement distributions at resonances are measured by laser interferometry for mode identification. It was applied to determine the piezoelectric coefficients and internal‐friction tensors as well as Cij of various piezoelectric materials, and also to thin‐film Cij. Because the contributions of the piezoelectric coefficients and thin‐film Cij to resonance frequencies are very small, correct mode identification becomes significantly important in their determination.