ON THE DETERMINATION OF SOUND SPEEDS IN CUBIC-CRYSTALS AND ISOTROPIC MEDIA USING A BROAD-BAND ULTRASONIC POINT-SOURCE POINT-RECEIVER METHOD

This paper describes methods for determining the speeds of elastic waves propagating in cubic single crystals using a broadband point-source and point-receiver, i.e., PS/PR, technique in which transient ultrasonic pulses are simultaneously propagated over a broad angular range of directions in a specimen. Emphasis is given to determination of all three wave speeds from one detected waveform resulting from a single excitation pulse. First described is the determination of both longitudinal and shear wave speeds in an isotropic solid from the waveform detected by an arbitrarily located sensor. Then, measurements made in various directions in [100]-, [110]-, and [111]-oriented silicon single crystal plates are analyzed. It is found that one obtains the most accurate determination of the three wave speeds from a single waveform detected by the sensors located in a {101}-type direction in both [100]- and [110]-oriented crystal specimens. It is found th at a pointlike capacitive displacement sensor generally yields better results for the wave-speed measurements than a pointlike piezoelectric transducer.