arXiv subjects

Tony Valier-Brasier

Publications and source records attributed to Tony Valier-Brasier.

3 recordsLinked to original sources

arXiv2026

Adiabatic Lamb modes in 3D tapered waveguides: Cut-off effects and ZGV resonances

This paper aims to enhance our understanding of the physical behavior of adiabatic modes in inhomogeneous elastic plates, particularly their remarkable capacity to adapt to gradual perturbations. The study investigates the propagation characteristics of higher-order adiabatic Lamb modes in waveguides with linearly varying thickness, with a focus on the influence of critical thicknesses on their propagation. This is achieved by leveraging the broadband excitation capabilities of a pulsed laser generating higher order Lamb modes to reveal various critical thicknesses, such as the cut-off and Zero-Group Velocity (ZGV) thicknesses. Remarkably, ZGV resonances can be induced at locations well beyond the laser source. Moreover, the mode's behavior is strongly influenced by thickness variations in all directions, imparting the plate an anisotropic-like behavior. Additionally, based on the observed effects, our experimental approach enables precise reconstruction of elastic waveguide profiles in additively manufactured aluminum plates with such thickness variations. The reconstructed profiles show a strong correlation with reference measurements across the scanned area.

physics.class-ph↗

arXiv2026

Tunneling of Elastic Waves in a Tapered Waveguide

Understanding how evanescent modes mediate energy transfer in tapered elastic waveguides is of paramount interest, as it unlocks new strategies for wave control and manipulation. Evanescent modes play a crucial role in energy localization and in the emergence of thickness resonances. We report the first unambiguous experimental evidence of Lamb mode tunneling near turning points, revealing how energy can traverse an evanescent barrier and recover its propagative nature after a finite transit time. Focusing on waveguides with linearly varying thickness, we show that the $S_2$ mode becomes evanescent over a narrow frequency band, enabling a tunnelinglike phenomenon. Our study demonstrates that the barrier width is governed by the elastic properties of the material, particularly the Poisson's ratio, within a confined range bordering the Dirac cone. Numerical results exhibit excellent agreement with predictions from the Wentzel-Kramers-Brillouin approximation. These findings provide compelling evidence that, for a specific barrier width, evanescent modes mediate energy transfer across regions classically forbidden to propagating waves, revealing the mechanisms governing transmission, localization, and mode conversion in structured or corrugated elastic waveguides.

physics.class-ph↗

arXiv2023

Experimental evidence of isotropic transparency and complete band gap formation for ultrasounds propagating in stealth hyperuniform media

Following on recent experimental characterization of the transport properties of stealth hyperuniform media for electromagnetic and acoustic waves, we report here measurements at ultrasonic frequencies of the multiple scattering of waves by 2D hyperuniform distributions of steel rods immersed in water. The transparency, for which the effective attenuation of the medium is cancelled, is first evidenced by measuring the transmission of a plane wave propagating in a highly correlated and relatively dense medium. It is shown that a band gap occurs in the vicinity of the first Bragg frequency. The isotropy of both transparency and bang gap are also evidenced for the case of waves generated by a point source in differently ordered and circular shaped distributions. In other words, we thus obtain a representation of the Green's function. Our results demonstrate the huge potential of hyperuniform as well as highly correlated media for the design of functional materials.

physics.flu-dyn↗