Backscattering enhancements from Rayleigh waves on the flat face of a tilted solid cylinder in water

When the face of a finite solid elastic cylinder is ensonified by an acoust ic wave, a variety of backscattering contributions associated with acoustic wave coupling into elastic waves are observed. A significant backscatterin g enhancement is observed for tilts such that the acoustic wave is incident on the face of the cylinder in the vicinity of the coupling angle for laun ching Rayleigh waves across the face. The observed backscattering indicates that the Rayleigh waves are reflected at the edge of the face and subseque ntly radiate acoustic waves in the backscattering direction. The measured b ackscattering is compared to an approximate theoretical prediction. Approxi mating the focusing of the Rayleigh wave after reflection at the (circular) edge by a Gaussian beam pressure distribution on the cylinder'S face yield s simple expressions for the amplitude which are consistent with the measur ements. In the vicinity of end-on incidence, other backscattering contribut ions due to the reflection of waves traveling down the length of the cylind er are observed. There is also evidence of a face-traversing longitudinal w ave for slightly tilted cylinders. (C) 2000 Acoustical Society of America. [S0001-4966(00)04601-4].