Bounded beam interaction with thin inclusions. Characterization by phase differences at Rayleigh angle incidence

A theoretical study of the reflection of a bounded Gaussian ultrasonic beam , incident onto a rectangular inclusion located near a fluid/solid half-spa ce interface, is presented. The thickness of the inclusion is assumed to be much smaller than the ultrasonic wavelength in the solid. It is shown that , at critical Rayleigh angle incidence, the phase in the point of maximum a mplitude of the shifted reflected lobe is very sensitive to dimension varia tions of the inclusion, and thus useful for inclusion characterization. The modelization of the problem is based on mode theory. (C) 2000 Acoustical S ociety of America. [S0001-4966(00)01510-1].