Publications by authors named "Gennady Shkerdin"

The nonlinear interaction between a high-frequency probing Lamb mode, propagating through a bilayer containing an initially closed tangential delamination at the interlayer interface whose contact conditions are dynamically changing because of a high-amplitude Lamb pump wave with long wavelength, is modeled in a quasi-stationary approach. The proposed criterion for the delamination to open is based on the magnitude, with respect to a threshold value, of the pump-wave-induced normal stress components that are pulling on both sides of the interface during part of its cycle. The temporal evolution of the contact condition during the pump wave cycle is calculated and the spectral enrichment caused by cross-modulation spectral components between the probing wave and the modulating wave is predicted.

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Three experimental laser ultrasonic configurations--line excitation with scanning detection, grating excitation with single point detection, and grating excitation with scanning probe beam--are shown to consistently reveal the modified propagation properties of Lamb waves on a polyethylene terephthalate (PET) film that is in contact with different liquids on its two sides. Theoretical predictions concerning the physical nature of different wave modes in symmetric and asymmetric film loading configurations (i.e.

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A theoretical study of Lamb mode propagation through an absorptive bilayer consisting of a steel plate coated by highly absorptive rubber with a finite delamination dividing these layers is presented. Essentially, in such a bilayer structure, steel-like A0 and S0 modes still propagate, although with moderate absorption. Two different types of delaminations are taken into consideration: slip delaminations in which noncontact boundary conditions are assumed only for shear displacement and stress, and stress-free delaminations in which noncontact boundary conditions are assumed for all mechanical displacements and stresses.

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This paper describes the history and the state of the art in radiation mode theory (RMT) in ultrasonics. The RMT originates from electromagnetism in which it has proved to be very efficient in the field of wave guides and discontinuities. In ultrasonics, the RMT made its entrance only a decade ago and has already proved to be very efficient in describing the interaction of sound with discontinuities such as a step on a plate, a liquid wedge, the extremity of a plate and much more.

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A theoretical study of the reflection of a two-dimensional Gaussian ultrasonic beam, incident at a Lamb angle of a plate containing a thin rectangular inclusion at an arbitrary position, is presented on the basis radiation mode theory. The inclusion is parallel to the plate surface and its thickness is assumed to be much smaller than the ultrasonic wavelength. It is shown that the amplitude and phase of the reflected beam profile can be used for accurate inclusion characterization.

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n-GaAs can be so highly doped that its plasma frequency is larger than the associated frequency of a CO2 laser emission line, leading to a negative real part of the dielectric permittivity. We studied linear and nonlinear reflection properties of structures composed of such thin highly doped n-GaAs film in an attenuated total reflection (ATR) configuration. We show that deep reflection minima coincide with the excitation of Brewster-type modes of the multilayer structure.

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