NORMAL-MODE THEORY OF NONSPECULAR PHENOMENA FOR A FINITE-APERTURE ULTRASONIC BEAM REFLECTED FROM LAYERED MEDIA

A normal-mode formalism is developed to describe the nonspecular effec ts of a finite-aperture ultrasonic beam incident onto layered elastic media. Analytical expressions for the reflected held have been obtaine d for various structures. This model proposed a unique physical pictur e and resolved the conflict between various explanations made for the nonspecular reflection phenomena. Novel features of leaky wave fields were observed at interfaces of liquid-solid and liquid-solid-liquid st ructures. These results may be helpful for nondestructive evaluation o f layered structures and determination of material signatures in the a coustic microscope. (C) 1997 American Institute of Physics.