ANOMALOUS REFLECTION OF ULTRASONIC BEAMS AT THE INTERFACE OF A SOLID MEDIUM WITH ATTENUATION
Résumé
Reflection of an oblique incident sound wave in liquid at the interface of a solid elastic medium with attenuation is examined. General expressions for modulus and phase of acoustic reflection coefficient are found. A field of the reflected ultrasonic beam is computed by the Fourier-integral method. It is shown that for incident angles which correspond to the Rayleigh wave excitation at solid-liquid interface a change in intensity of the reflected beam is to be observed in addition to a sideways displacement of the beam. Both mentioned effects depend strongly on rate of acoustic energy loss in the medium. For attenuation exceeding some critical value (when active impedance constituent of a medium is equal to the liquid impedance) the reflection is anomalous, displacement practically vanishes and instead of a displacement an abrupt decrease of a reflected beam intensity takes place. Comparison of peculiarities of an ultrasonic beam reflection from media with different attenuation is demonstrated by Toepler shadow method. Experimental data are in accordance with the theory. These peculiarities can be used for studying characteristics of elastic surface and pseudosurface waves on anisotropic crystals.
Domaines
Articles anciensOrigine | Accord explicite pour ce dépôt |
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