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The dual space process of mode conversions for the interaction of Lamb wave with a periodic grating is described. The coupling of modes is related to the opening of the band gaps in the fold-back dispersion curves in the first Brillouin zone.

The aim of this paper is to provide an analytical contribution which presents the application of shear-horizontal (SH)-guided waves for the characterisation of a bi-layered structure which consists of two isotropic plates adhesively bonded using a non-dissipative thin layer of glue. The thickness of the layer of glue is assumed to be non-negligible, and the interfaces between this layer of glue and the plates are both assumed to be roughened (parallel ridges with complex shape and depth profiles). The basis of the theoretical approach is an extension of the integral formulation, in the frame of SH modal couplings due to the roughness, which has been developed previously for SH-wave propagation over a single plate with a rough surface. This approach assumes that the average roughness height is a small fraction of the thicknesses of the waveguides (the plates) everywhere. The changes, due to the roughness, in the characteristics of the fields created by a harmonic source set at the entrance edge of the structure are expressed through the mapping of the displacement and stress perturbations. Preliminary tests of the effectiveness of the model are given; they rely on the phase-matching effects of periodic profiles and pseudo-random experimental profile. [ABSTRACT FROM AUTHOR]

This paper aims at providing analytical and numerical approaches to analyze the behavior of guided waves (Lamb-type waves) propagating inside plates with a rough surface considered here as distributed small perturbations. A physical interpretation of the attenuation phenomenon of the propagating mode generated by the source (mode coupling) is provided for an ideal rough plate (fluid plate) using an analytical model available in the literature. This analytical model is validated using a numerical method. The obtained results on periodically corrugated surfaces of fluid plates emphasize the role played by the spatial period and the modal coupling. They serve also as results for interpreting the effect due to randomly rough surfaces in solid plates, notably the effect of the power spectrum density of the rough profile (including the effect of the statistical roughness parameters mentioned in Part I). The results obtained experimentally and theoretically, for the attenuation factor of the main Lamb wave, are found close to one another. [ABSTRACT FROM AUTHOR]

The characterization of bounded roughened surfaces before applying adhesive joint, in order to detect poor cohesive and adhesive properties, remains difficult. Earlier studies based on analysis of surface wave (Rayleigh waves or Scholte waves) are not really adapted to the characterization of such surfaces. Guided acoustic waves, i.e., Lamb waves, turn out to be the best adapted kind of waves to characterize this roughness when plates are bounded together. It is the aim of this paper to provide analytical and experimental approaches to analyze the behavior of Lamb waves propagating inside plates with a rough surface (small perturbations). First, experimental results of the attenuation effects are given on roughened glass plates. Second, the attenuation factor of the Lamb wave in an anisotropic rough solid plate is calculated through a complex analytical model of the dispersion equation which accounts for the effect of the power spectrum density of the rough profile (including the effect of the statistical roughness parameters). [ABSTRACT FROM AUTHOR]