Resonant ultrasound spectroscopy: Applications, current status and limitations

Over the last 10 years, resonant ultrasound spectroscopy (RUS) has become a versatile laboratory technique for measuring second-order elastic constants and ultrasonic attenuation in solids. The technique is based on measuring the spectrum of mechanical resonances for a sample of known shape (usually a parallelepiped). This spectrum cannot be deconvoluted to deduce the elastic constants. Instead, an approximate spectrum is calculated from the known sample dimensions, its mass, and a set of `guessed' elastic constants. A multidimensional minimization of the error between the measured and calculated spectra enables deducing all the elastic constants of the solid from a single frequency scan. Currently, the technique can be applied to crystals of orthorhombic symmetry (9 elastic constants) or higher using desktop computers and software developed for this purpose.