Experimental and numerical study of the excitability of zero group velocity Lamb waves by laser-ultrasound

Grünsteidl, Clemens; Veres, István A.; Murray, Todd W.

doi:10.1121/1.4922701

Cited by 39 publications

(9 citation statements)

References 25 publications

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“…The maxima of these curves are in good agreement with theoretical calculations. These results are coherent with the approximation (w ≈ 0.3λ S1S2 ) given for an aluminium plate by Balogun et al 17 Other results were obtained by Grnsteidl et al in a 250-µm thick tungsten plate 19 of Poisson's ratio ν = 0.284 and shear velocity c s = 2668 m/s. With these parameters, the wavelength is λ S1S2 = 3.7 × 2h mm, so that the optimal beam radius to plate thickness ratio is…”

Section: A Optimization Of a Gaussian Beamsupporting

confidence: 89%

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Laser beam shaping for enhanced Zero-Group Velocity Lamb modes generation

Bart

Laurent

Jehanno

et al. 2016

The Journal of the Acoustical Society of America

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Optimization of Lamb modes induced by laser can be achieved by adjusting the spatial source distribution to the mode wavelength (λ). The excitability of Zero-Group Velocity (ZGV) resonances in isotropic plates is investigated both theoretically and experimentally for axially symmetric sources. Optimal parameters and amplitude gains are derived analytically for spot and annular sources of either Gaussian or rectangular energy profiles. For a Gaussian spot source, the optimal radius is found to be λ/π. Annular sources increase the amplitude by at least a factor of 3 compared to the optimal Gaussian source. Rectangular energy profiles provide higher gain than Gaussian ones. These predictions are confirmed by semi-analytical simulation of the thermoelastic generation of Lamb waves, including the effect of material attenuation. Experimentally, Gaussian ring sources of controlled width and radius are produced with an axicon-lens system. Measured optimal geometric parameters obtained for Gaussian and annular beams are in good agreement with theoretical predictions. A ZGV resonance amplification factor of 2.1 is obtained with the Gaussian ring. Such source should facilitate the inspection of highly attenuating plates made of low ablation threshold materials like composites.

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Section: A Optimization Of a Gaussian Beamsupporting

confidence: 89%

“…This question was then addressed by Grunsteidl et al experimentally and numerically using a time domain finite difference technique. 19 They found, for tungsten, an optimal radius between 1.0 and 1.1 times the plate thickness.…”

Section: Introductionmentioning

confidence: 97%

Laser beam shaping for enhanced Zero-Group Velocity Lamb modes generation

Bart

Laurent

Jehanno

et al. 2016

The Journal of the Acoustical Society of America

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“…The filter was necessary as the absorbed energy from the laser heated the surrounding air leading to the variation of the index Δn in the optical path of the probe beam. This induced an additional phase shift Δϕ n and a large low-frequency voltage that would otherwise saturate the electronics detection unit 78 . A video of a typical signal acquisition is provided in Supplementary Movie 1.…”

Section: Methodsmentioning

confidence: 99%

Laser-excited elastic guided waves reveal the complex mechanics of nanoporous silicon

et al. 2021

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Nanoporosity in silicon leads to completely new functionalities of this mainstream semiconductor. A difficult to assess mechanics has however significantly limited its application in fields ranging from nanofluidics and biosensorics to drug delivery, energy storage and photonics. Here, we present a study on laser-excited elastic guided waves detected contactless and non-destructively in dry and liquid-infused single-crystalline porous silicon. These experiments reveal that the self-organised formation of 100 billions of parallel nanopores per square centimetre cross section results in a nearly isotropic elasticity perpendicular to the pore axes and an 80% effective stiffness reduction, altogether leading to significant deviations from the cubic anisotropy observed in bulk silicon. Our thorough assessment of the wafer-scale mechanics of nanoporous silicon provides the base for predictive applications in robust on-chip devices and evidences that recent breakthroughs in laser ultrasonics open up entirely new frontiers for in-situ, non-destructive mechanical characterisation of dry and liquid-functionalised porous materials.

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“…The filter was necessary as the absorbed energy from the laser heated the surrounding air leading to the variation of the index ∆n in the optical path of the probe beam. This induced an additional phase shift ∆φ n and a large low frequency voltage that would otherwise saturate the electronics detection unit [45]. A video of a typical signal acquisition FIG.…”

Section: Elastic Guided Waves Measurementsmentioning

confidence: 99%

Laser-Excited Elastic Guided Waves Reveal the Complex Mechanics of Nanoporous Silicon

Thelen,

Bochud,

Brinker

et al. 2020

Preprint

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Nanoporosity in silicon leads to completely new functionalities of this mainstream semiconductor. A difficult to assess mechanics has however significantly limited its application in fields ranging from nanofluidics and biosensorics to drug delivery and energy storage. Here, we present a study on laser-excited elastic guided waves detected contactless and non-destructively in dry and liquid-infused single-crystalline porous silicon. These experiments reveal that the self-organized formation of 100 billions of parallel nanopores per square centimeter cross section results in an isotropic elasticity perpendicular to the pore axes and an 80% stiffness reduction in the material, despite a bulk-like and anisotropic pore-wall elasticity. Our complete assessment of the waferscale mechanics of nanoporous silicon provides the base for predictive applications in robust on-chip devices and evidences that recent breakthroughs in laser ultrasonics open up entirely new frontiers for in-situ, nondestructive mechanical characterisation of dry and liquid-functionalised porous materials.

show abstract

Experimental and numerical study of the excitability of zero group velocity Lamb waves by laser-ultrasound

Cited by 39 publications

References 25 publications

Laser beam shaping for enhanced Zero-Group Velocity Lamb modes generation

Laser beam shaping for enhanced Zero-Group Velocity Lamb modes generation

Laser-excited elastic guided waves reveal the complex mechanics of nanoporous silicon

Laser-Excited Elastic Guided Waves Reveal the Complex Mechanics of Nanoporous Silicon

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