INHOMOGENEOUS PLANE-WAVE SCATTERING AND MODE STIMULATION ON PERIODIC ROUGH SURFACES

Medium vibration properties to characterize interface layers and quali ty of bonding can be examined by an ordinary approach using homogeneou s waves or by a more general inhomogeneous (or complex harmonic) wave scattering technique. It is known that only particular inhomogeneous p lane waves can stimulate eigenvibrations of a given structure, and not the homogeneous wave. The reflection and transmission of such inhomog eneous waves is investigated for plane parallel interfaces as well as their scattering at periodically corrugated boundaries between liquid and solids. The influence of plate thickness, corrugation periodicity, and height on the occurrence of specific plate modes is examined. Usi ng an alternative description of a bounded ultrasonic beam as a finite superposition of inhomogeneous waves, this theory can be applied to e xamine the deformation of Gaussian profiles and to explicitly relate t his deformation to the stimulation of mode vibrations. The generation of a plate-or interface-mode by an obliquely incident single inhomogen eous wave on a plane parallel plate-or half-space interface boundary-a nd the scattering of inhomogeneous waves at the interface wave stimula ted corrugated surface, also suggest a new interpretation of back refl ection and transmission of bounded beams at smooth liquid-solid interf aces. (C) 1996 Acoustical Society of America.