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Dive into the research topics where P Leclaire is active.

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Featured researches published by P Leclaire.


Journal of the Acoustical Society of America | 1996

Determination of the viscous characteristic length in air‐filled porous materials by ultrasonic attenuation measurements

P Leclaire; Luc Kelders; Walter Lauriks; Christ Glorieux; Jan Thoen

The concept of viscous characteristic length is used to describe the acoustical behavior of fluid‐saturated porous media in the high‐frequency regime. A method to determine this parameter consists of measuring the wave attenuation in the high‐frequency limit. This method has already been used for porous materials saturated by superfluid 2He. It is tested in the case of air‐filled absorbent materials in a frequency range of [50–600 kHz]. The thermal characteristic length is assumed to be known or measured independently. Two examples are presented. In the first one the method is usable and the viscous characteristic length Λ is deduced from the high‐frequency behavior of the attenuation per cycle. In the second example, an additional attenuation occurs at high frequencies and only an estimate of Λ can be given. Nevertheless, the estimation appears to be rather accurate. The values obtained by this method are compared to those determined by a nonlinear fit of the dispersion curves.


Applied Physics Letters | 1996

ULTRASONIC WAVE PROPAGATION IN RETICULATED FOAMS SATURATED BY DIFFERENT GASES : HIGH FREQUENCY LIMIT OF THE CLASSICAL MODELS

P Leclaire; Luc Kelders; Walter Lauriks; Jean François Allard; Christ Glorieux

Transmission experiments are performed on high porosity reticulated polyurethane foams saturated by different gases at ultrasonic frequencies up to 800 kHz. An excess attenuation is observed at high frequencies, when the wavelength is not sufficiently large compared to the lateral dimensions of the fibers. At lower frequencies, these experiments lead by using classical models of equivalent fluids, to a fast and reliable method for determining the characteristic length Λ.


Journal of the Acoustical Society of America | 2011

Propagation of acoustic waves in a one-dimensional macroscopically inhomogeneous poroelastic material

G. Gautier; Luc Kelders; Jean-Philippe Groby; Olivier Dazel; L. De Ryck; P Leclaire

Wave propagation in macroscopically inhomogeneous porous materials has received much attention in recent years. The wave equation, derived from the alternative formulation of Biots theory of 1962, was reduced and solved recently in the case of rigid frame inhomogeneous porous materials. This paper focuses on the solution of the full wave equation in which the acoustic and the elastic properties of the poroelastic material vary in one-dimension. The reflection coefficient of a one-dimensional macroscopically inhomogeneous porous material on a rigid backing is obtained numerically using the state vector (or the so-called Stroh) formalism and Peano series. This coefficient can then be used to straightforwardly calculate the scattered field. To validate the method of resolution, results obtained by the present method are compared to those calculated by the classical transfer matrix method at both normal and oblique incidence and to experimental measurements at normal incidence for a known two-layers porous material, considered as a single inhomogeneous layer. Finally, discussion about the absorption coefficient for various inhomogeneity profiles gives further perspectives.


Journal of Applied Physics | 2005

Guided elastic waves in porous materials saturated by air under Lamb conditions

Laurens Boeckx; P Leclaire; Poonam Khurana; Christ Glorieux; Walter Lauriks; Jean François Allard

The propagation of guided elastic waves in porous materials saturated by air under Lamb conditions is studied theoretically and experimentally. The modes are derived from expressing the boundary conditions on the normal and tangential stresses and the displacements at the interfaces between the porous layer and the surrounding fluid. The stresses and the fluid pressure inside the porous medium are obtained from Biot’s equations of poroelasticity. Symmetrical and antisymmetrical modes are found when the porous layer is loaded by the same fluid on both sides. Damping mechanisms include viscous and thermal exchanges between the solid and the fluid, in addition to the classical structural damping. Using an experimental setup based on the generation of standing waves in the layer and taking the spatial Fourier transform of the displacement profile, the phase velocities of three modes were measured for two porous materials in a frequency range between 80 Hz and 4 kHz. The measurements confirm the theoretical pr...


Journal of the Acoustical Society of America | 2008

Reconstruction of material properties profiles in one-dimensional macroscopically inhomogeneous rigid frame porous media in the frequency domain.

L. De Ryck; Walter Lauriks; P Leclaire; Jean-Philippe Groby; Armand Wirgin; C Depollier

The present paper deals with the inverse scattering problem involving macroscopically inhomogeneous rigid frame porous media. It consists of the recovery, from acoustic measurements, of the profiles of spatially varying material parameters by means of an optimization approach. The resolution is based on the modeling of acoustic wave propagation in macroscopically inhomogeneous rigid frame porous materials, which was recently derived from the generalized Biots theory. In practice, the inverse problem is solved by minimizing an objective function defined in the least-square sense by the comparison of the calculated reflection (and transmission) coefficient(s) with the measured or synthetic one(s), affected or not by additive Gaussian noise. From an initial guess, the profiles of the x-dependent material parameters are reconstructed iteratively with the help of a standard conjugate gradient method. The convergence rate of the latter and the accuracy of the reconstructions are improved by the availability of an analytical gradient.


Journal of Applied Physics | 2007

Surface acoustic wave depth profiling of a functionally graded material

Jozefien Goossens; P Leclaire; Xiaodong Xu; Christ Glorieux; Loic Martinez; Antonella Sola; Cristina Siligardi; Tom Van der Donck

The potential and limitations of Rayleigh wave spectroscopy to characterize the elastic depth profile of heterogeneous functional gradient materials are investigated by comparing simulations of the surface acoustic wave dispersion curves of different profile-spectrum pairs. This inverse problem is shown to be quite ill posed. The method is then applied to extract information on the depth structure of a glass-ceramic (alumina) functionally graded material from experimental data. The surface acoustic wave analysis suggests the presence of a uniform coating region consisting of a mixture of Al2O3 and glass, with a sharp transition between the coating and the substrate. This is confirmed by scanning electron microscope with energy dispersive x-ray analysis.


Journal of Applied Physics | 2016

Spatial Laplace transform for complex wavenumber recovery and its application to the analysis of attenuation in acoustic systems

Alan Geslain; Samuel Raetz; Morgan Hiraiwa; M. Abi Ghanem; S. P. Wallen; Nicholas Boechler; Jérôme Laurent; Claire Prada; Aroune Duclos; P Leclaire; Jean-Philippe Groby

We present a method for the recovery of complex wavenumber information via spatial Laplace transforms of spatiotemporal wave propagation measurements. The method aids in the analysis of acoustic attenuation phenomena and is applied in three different scenarios: (i) Lamb-like modes in air-saturated porous materials in the low kHz regime, where the method enables the recovery of viscoelastic parameters; (ii) Lamb modes in a Duralumin plate in the MHz regime, where the method demonstrates the effect of leakage on the splitting of the forward S1 and backward S2 modes around the Zero-Group Velocity point; and (iii) surface acoustic waves in a two-dimensional microscale granular crystal adhered to a substrate near 100u2009MHz, where the method reveals the complex wavenumbers for an out-of-plane translational and two in-plane translational-rotational resonances. This method provides physical insight into each system and serves as a unique tool for analyzing spatiotemporal measurements of propagating waves.


IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control | 2006

Study of the bending modes in circular quartz resonators

P Leclaire; Jozefien Goossens; Loic Martinez; Nicolas Wilkie-Chancelier; Stéphane Serfaty; Christ Glorieux

An experimental and theoretical study of bending modes in a partially electroded circular piezoelectric quartz (AT-cut) with free edge is presented. The quartz is excited by a voltage pulse applied on the electrodes, and its surface is scanned by a laser vibrometer that measures the out-of-plane displacements. The classical theory of bending of thin disks is used to describe the flexural modes at frequencies lower than the first thickness shear resonance (6 MHz). A fairly good agreement is found between experimental and theoretical results for the forced mode shapes and for the resonance frequencies. However, it appears that the two springs used to maintain the disk in position introduce extra clamping conditions. Several source shapes were studied, among which a collection of an arbitrary number of forces is particularly useful. The two-dimensional wavenumber representation shows the presence of anisotropy related to the crystallographic axes at higher frequencies, which is not predicted by the model. The experimental phase velocities are compared to those given by the classical theory of disks and to those of Lamb A0 mode. This study confirms the correspondence at low frequencies between the A0 mode and the bending eigenmodes of a disk with finite size


Acta Acustica United With Acustica | 2011

Study of Circumferential Waves on a Poroelastic Cylinder

Jan Descheemaeker; Christ Glorieux; Walter Lauriks; Jean-Philippe Groby; P Leclaire; Laurens Boeckx

J. Descheemaeker1), C. Glorieux1), W. Lauriks1), J. P. Groby2), P. Leclaire3), L. Boeckx4) 1) Laborature Acoustical and Thermal Fysica, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium. [email protected] 2) Laboratoire d’Acoustique de l’Université du Maine, UMR CNRS 6613, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France. 3) Institut Supérieur de l’Automobile et des Transports Université de Bourgogne, 49 Rue Mademoiselle Bourgeois, 58027 Nevers Cedex, France. 4) Huntsman Europe, Everslaan 45, 3078 Everberg, Belgium.


Acustica | 1997

Prediction and measurements of the influence of boundary conditions in a standing wave tube

T.E. Vigran; Luc Kelders; Walter Lauriks; P Leclaire; Tf Johansen

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Walter Lauriks

Katholieke Universiteit Leuven

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Luc Kelders

Katholieke Universiteit Leuven

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Laurens Boeckx

Katholieke Universiteit Leuven

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Poonam Khurana

Katholieke Universiteit Leuven

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Jean François Allard

Centre national de la recherche scientifique

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Jean-Philippe Groby

Centre national de la recherche scientifique

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Bert Roozen

Katholieke Universiteit Leuven

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Bert Verstraeten

Katholieke Universiteit Leuven

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Jan Thoen

Katholieke Universiteit Leuven

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