Right-Angle Reflector Technique for the Ultrasonic Examination of Material Properties

Abstract

An ultrasonic goniometer is described that utilizes a single transducer and a reflector composed of two plane orthogonal surfaces. With the instrument immersed in a suitable coupling liquid, the transducer rotates about an axis colinear with the intersection of the orthogonal surfaces. The amplitude of the reflected signal is automatically recorded versus the angle of incidence measured relative to one of the reflector walls (the removable specimen). Amplitude variations can be related to the excitation of surface waves, Lamb waves, critical refraction conditions for body waves, and other physical properties of the reflecting surfaces. The instrument has been extremely useful in measuring surface wave velocities for both single crystal and polycrystalline specimens. On copper and quartz single crystals, good agreement has been achieved with theoretical predictions of surface wave velocity as a function of propagation direction. [Phys. Rev. 119, 533 (1960); J. Acoust. Soc. Am. 41, 921 (1967)]. The sensitivity of the device to other physical parameters will be discussed. [Work supported in part by the Office of Naval Research].