Rayleigh wave layered surfaces

Based upon a piezoelectric 1-3-composite material, air-bome ultrasonic probes for frequencies up to 2 MHz were developped. These probes are characterized by a bandwidth larger than 50 % as well as a signal-to-noise ratio higher than 100 dB. Applications are the thickness measurement of thin powder layers, the inspection of sandwich structures, the detection of surface near cracks in metals or ceramics by generation/reception of Rayleigh waves and the inspection of plates by Lamb waves. 

Rednikov, A. Ye., Colinet, P, Velarde, M. G., and Legros, J. C. (2000) Rayleigh-Marangoni oscillatory instability in a horizontal liquid layer heated from above coupling between internal and surface waves. J. Fluid Mech. 405 57-77. 

More recently (in the last 25 years or so), surface wave methods have become popular for measurement of shear wave velocity. These include SASW (spectral analysis of surface waves, e.g. Stokoe et al, 1994), see Appendix B 5.3.6 and MASW (or multichannel analysis of surface waves, e.g. www.masw.com by Park Seismic LLC). The basis of the technique is the dispersive property of Rayleigh-type surface waves when propagating in a layered system. No subsurface drilling or equipment is needed, but more sophisticated data processing is required to determine the shear wave velocity. 

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