Verification of crystal elastic anisotropy theory by ultrasonic diffraction experiments

This paper points out an indirect but convincing experimental verification of certain theories concerning elastic-wave propagation in anisotropic media. Relations between the Poynting vector and the propagation vector for longitudinal wave propagation near, but not exactly parallel to, certain pure-mode axes permit the calculation of the ultrasonic diffraction from large single apertures (transducers) oriented for propagation exactly along the pure-mode axes. Then the diffraction loss versus distance, measured in oriented single crystals, permits the verification of the theories concerning these relations and concerning ultrasonic diffraction. It is shown that five items of theory have been verified by the ultrasonic diffraction measurements.