Dominique Décultot
Centre national de la recherche scientifique
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Featured researches published by Dominique Décultot.
Journal of the Acoustical Society of America | 1992
Fernand Léon; Florence Lecroq; Dominique Décultot; Gérard Maze
Acoustic scattering from an isotropic elastic hollow cylindrical shell of infinite length excited by an obliquely incident plane acoustic wave is investigated. The form functions of an aluminum cylindrical shell immersed in water have been calculated by the direct summation of the Rayleigh series. Computations are made at angles (with the normal to the cylinder axis) between α=0° and α=35°. The results of the theoretical calculation are in good agreement with the results of experiments. The experimental results have shown in a frequency range of k1a=0 –20 that the resonances are related to three wave families: the circumferential wave (l=2) detected for angles smaller than the ‘‘angle of longitudinal wave in thin rods’’ (αl), the guided wave (p=1) detected for angles smaller than the second critical angle (αT), and the Scholte–Stoneley wave (l=0). The evolution of the resonance frequencies is followed for different angles and one can note experimentally, that at an angle superior to the Rayleigh critical ...
Measurement Science and Technology | 2006
N Taifi; F Bakkali; B Faiz; A Moudden; Gérard Maze; Dominique Décultot
A non-invasive ultrasonic method was used to control the change in physical properties of milk gel and the syneresis, which is an essential step in the manufacture of cheese. The velocity and the attenuation were recorded for ten hours. They provide a good indicator of syneresis occurring. The firmness of the milk gel increases with the variation in velocity (ΔV). The effects of the temperature, calcium chloride and rennet concentration on the syneresis were studied.
Journal of the Acoustical Society of America | 2002
Lionel Haumesser; Dominique Décultot; Fernand Léon; Gérard Maze
Acoustic scattering from a finite air-filled elastic cylindrical shell, immersed in water, is investigated. The shell is made of stainless steel and has a thickness to outer radius ratio of 17%. The considered dimensionless frequency range extends over 7 << k1a << 22 (k1: wave number in water, a: outer radius). Bistatic measurements are carried out to identify vibration modes related to the phase matching of the first guided wave, T0, propagating on the shell. Both transducers, the emitter and the receiver, are positioned at the same angular distance with regard to the normal axis of the shell. The emitter transducer is fixed at a given position. In order to identify circumferential modes of vibration, the receiver transducer is made to rotate in the azimuthal plane, normal to the shell axis. Results obtained are plotted in functions of dimensionless frequency and azimuthal angle. Vibration modes along the shells length are identified by moving the receiver transducer parallel to the shell axis. In this case, results are plotted in functions of dimensionless frequency and axial wave number. The experimental investigation is corroborated by theoretical results obtained from approximate calculations for thick finite cylindrical shells [Scot F. Morse et al., J. Acoust. Soc. Am. 103, 785-794 (1998)]. The evolution of the mode position with respect to the incidence angle is discussed so as to clarify peak patterns in backscattered resonance spectra.
Measurement Science and Technology | 2000
Rachid Latif; E Aassif; Gérard Maze; Dominique Décultot; A Moudden; B Faiz
This paper presents a study of the group velocity dispersion of some circumferential waves propagating around an elastic tube. The dispersive character of the circumferential waves is theoretically known, but the experimental measurement of the group velocity in a dispersive medium is still a complex operation. We have determined the characteristics of the circumferential wave dispersion for aluminium and steel tubes using a time-frequency representation. Among these time-frequency techniques, the Wigner-Ville distribution (WVD) is used here for its interesting properties in terms of acoustic applications. The WVD is applied to the analysis of the dispersion of S0 symmetric and A1 antisymmetric circumferential waves propagating around a tube with a radii ratio equal to 0.95 (internal radius:external radius). This allowed us to determine their group velocities and reduced cutoff frequencies. The results obtained are in good agreement with the calculated values using the proper modes theory.
Journal of the Acoustical Society of America | 2001
Lionel Haumesser; André Baillard; Dominique Décultot; Gérard Maze
Acoustic backscattering from elastic cylindrical shells of finite lengths, immersed in water, is investigated. These objects, characterized by the ratio of length over diameter (L/2a = 9.76, 4.88, 2.44, a: outer radius), are excited by an obliquely incident plane acoustic wave. In the three cases studied here, the radii ratio b/a (b: inner radius) is fixed at 0.97. The investigated dimensionless frequency range extends over 10 k1a < or = 50 (k1 : wave number in water). The first guided wave, T0, is of particular interest here. The influence of the shells length on the backscattered pressure is experimentally observed in the time-angle and frequency-angle representations. In support of this experimental study, a time-domain representation is used by extending a theoretical model that provides a geometrical description of the helical propagation of the surface waves around the shell [Bao, J. Acoust. Soc. Am. 94, 1461-1466 (1993)]. Theoretical results on cylindrical shells considered as infinitely long, with identical characteristics, are compared with both experimental representations.
Journal of the Acoustical Society of America | 2000
André Baillard; Jean-Marc Conoir; Dominique Décultot; Gérard Maze; Aleksander Klauson; Jaan Metsaveer
The acoustic scattering from a fluid-loaded stiffened cylindrical shell is described by using elasticity theory. The cylindrical shell is reinforced by a thin internal plate which is diametrically attached along the tube. In this model, cylindrical shell displacements and constraints expressed from elasticity theory are coupled to those of the plate at the junctions, where plate vibrations are described by using plate theory. The present model is first validated at low frequency range (k1a approximately 5-40) by comparison with a previous model based on the Timoshenko-Mindlin thin shell theory and by experimental results. Theoretical and experimental resonance spectra are then analyzed in a high frequency range (k1a approximately 120-200). Only resonances due to the S0 wave are clearly observed in this frequency range, and their modes of propagation are identified. Furthermore, A0 wave propagation is detected, because of the presence of the reflection of this wave at the shell-plate junctions.
Journal of the Acoustical Society of America | 2000
N. Touraine; L. Haumesser; Dominique Décultot; Gérard Maze; Aleksander Klauson; Jaan Metsaveer
Through an experimental approach, in this paper we investigate the acoustic wave scattering processes involved in the acoustic backscattering at variable incidences from an air-filled submerged cylindrical shell with hemispherical endcaps. Given the 1% shell thickness and the explored low frequency domain, the wave types studied are the circumferential or helical S0 wave and the helical T0 wave only. Between the axial (in the direction of the main axis of the object) and the normal incidences (normal to the main axis), two distinct angular zones can be observed depending on hemispherical or cylindrical excitation. In these zones, after a pressure wave excitation, different series of echoes on the echo wave forms are identified by their arrival times and related wave types. From results in the time domain and those obtained in the frequency domain, each acoustic response from the target corresponding to the two zones of excitation is compared with the acoustic response of canonical objects (spherical shell for axial excitation and tube for normal excitation). This analysis of the acoustic response from the target at various incidences, highlights the influence of both the endcaps and the finite length for a cylindrical shell on scattering. The study is intended to make a contribution to the knowledge of the identification of such geometrically complex objects.
Journal of the Acoustical Society of America | 1996
Aleksander Klauson; Jaan Metsaveer; Dominique Décultot; Gérard Maze; J. Ripoche
A theoretical and experimental study of the acoustic response of a submerged stiffened cylindrical shell is presented. The internal rib is modeled as a clamped‐free plate mounted inside the shell perpendicular to the shell surface. The stiffened shell is excited by a normally incident acoustic pressure wave. Wave propagation around the circumference of the shell and associated sound radiation are discussed. From the directivity of the monostatic scattering, the resonances in the scattered sound pressure field can be separated into three different types. A mechanical admittance is used to help identify the different types of resonances excited in the fluid‐loaded stiffened shell. Each type of resonance is shown to be associated with a particular type of interaction between the shell and the rib in terms of the components of the coupling forces: i.e., the normal force, the transverse force, and the coupling moment. For kR ranging from 16 to 35, the normal coupling force is shown to control the symmetric fle...
Journal of the Acoustical Society of America | 1991
Gérard Maze; Florence Lecroq; Dominique Décultot; J. Ripoche; Susan K. Numrich; H. Überall
The acoustic scattering from infinite elastic cylinders or spheres is well known. It is possible to characterize these targets by their resonance spectra. The resonances are established by the generation of surface waves that propagate around the circumference of the targets. The resonances originate from the phase matching of repeatedly circumnavigating surface waves. Experimentally, it is possible to characterize a target with a complicated shape, but it is not easy to explain the spectra theoretically because the geometry is not separable and the usual analytical methods to calculate the far‐field pressure cannot be used. In this paper, resonance spectra and angular diagrams obtained from a target consisting of a finite cylinder with hemispherical endcaps are obtained experimentally. To explain the resonance spectra, an integral phase matching condition is used. Upon incidence normal to the cylinder axis, resonances due to the phase matching of surface waves traveling along a circumference or along a m...
Journal of the Acoustical Society of America | 2005
Romain Liétard; Dominique Décultot; Gérard Maze; Michel Tran-Van-Nhieu
The influence of evenly spaced ribs (internal rings) on the acoustic scattering from a finite cylindrical shell is examined over the dimensionless frequency range 1<ka<42 (where k is the wave number in water and a the outer radius of the cylinder). Experimental results, obtained with a monostatic setup, are discussed in the incidence angle/time and incidence angle/frequency domains. The physical phenomena that give rise to highlights in the experimental spectra (Bragg scattering and scattering from Bloch-Floquet waves) are investigated. Fast Fourier Transform (FFT) processing on different segments of time signals allows us to distinguish influences of these phenomena. Further, comparison is made between frequency based results and numerical results provided by, respectively, a theoretical model using the thin shell theory [Tran-Van-Nhieu, J. Acoust. Soc. Am. 110, 2858–2866 (2001)] and a simple scattering/interference calculation.