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## Publications

Publications (302)

In this article, an improvement of [1] is proposed, in order to identify the flexural and shear complex moduli of a sandwich beam by simply measuring the displacement field. The method described here involves a correction of finite the difference scheme 5

This paper addresses the problem of estimating the local viscoelastic parameters of sandwich beams. An original procedure involving an inverse vibratory method (Force Analysis Technique) and the Timoshenko beam theory is detailed and applied experimentally on a sample presenting a honeycomb core. The major philosophy relies in considering multi-lay...

Vibro-acoustic simulation in the mid-frequency range is of interest for automotive and truck constructors. The dissipative treatments used for noise and vibration control such as viscoelastic patches and acoustic absorbing materials must be taken into account in the problem. The Statistical modal Energy distribution Analysis (SmEdA) model consists...

De nombreux travaux dans la littérature se sont concentrés sur la modélisation vibro-acoustique de coques cylindriques raidies immergées, du fait des nombreuses applications industrielles, en particulier dans le domaine aéronautique ou naval. Cependant, peu d’études prennent en compte des structures internes non-axisymétriques. En effet, des struct...

A method for reconstructing and separating vibratory field on a plate-like structure is presented. The method, called “Structural Holography” is derived from classical Near-field Acoustic Holography (NAH) but in the vibratory domain. In this case, the plate displacement is measured on one-dimensional lines (the holograms) and used to reconstruct th...

This paper presents the theoretical framework of the virtual acoustic volume concept and two related inverse Patch Transfer Functions (iPTF) identification methods (called u-iPTF and m-iPTF depending on the chosen boundary conditions for the virtual volume). They are based on the application of Green's identity on an arbitrary closed virtual volume...

The source field reconstruction aims at identifying the excitation field measuring the response of the system. In Near-field Acoustic Holography, the response of the system (the radiated acoustic pressure) is measured on a hologram using a microphones array and the source field (the acoustic velocity field) is reconstructed with a back-propagation...

A perfect diffuse acoustic field is theoretically required when performing measurements that make use of a reverberant room. From an experimental point of view, completely diffuse conditions are impossible to reach and ensuring an as effective as possible sound diffusion in the room becomes of crucial practical importance. The diffusivity indicator...

Statistical modal Energy distribution Analysis (SmEdA) approach was developed to enlarge the application field of Statistical Energy Analysis (SEA) when equipartition of modal energies is not achieved. SmEdA gives more precise results than standard SEA when compared to exact energy response of a deterministic system in the case of low modal overlap...

This article presents the modeling of a MEMS microphone with an original architecture formed of mechanical structures moving in the plane of the substrate. On the contrary of most microphones generally constituted of an oscillating membrane, some transducers developed by the CEA-LETI with M&NEMS technology use micro beams moving in the plane of the...

An as diffuse as possible acoustic field is pursued when performing measurements that make use of a reverberant room. The diffusivity descriptors that are commonly used to qualify the actual sound field in such a room are calculated in the room volume, away from boundaries. This is somewhat contradictory with the fact that for sound insulation and...

L’étude du rayonnement acoustique des coques cylindriques raidies a fait l’objet de nombreux travaux car elles sont d’un grand intérêt pour les industriels des secteurs naval et aéronautique. Cependant peu d’attention a été portée aux effets liés à la présence de structures fixées rigidement à l’intérieur de la coque, telles que des planchers, des...

The vibroacoustic behavior of axisymmetric stiffened shells immersed in water has been intensively studied in the past. On the contrary, little attention has been paid to the modeling of these shells coupled to non-axisymmetric internal frames. Indeed, breaking the axisymmetry couples the circumferential orders of the Fourier series and considerabl...

Substructuring approaches are nowadays widely used to predict numerically the vibroacoustic behavior of complex mechanical systems. Some of these methods are based on admittance or mobility frequency transfer functions at the coupling interfaces. They have already been used intensively to couple subsystems linked by point contacts and enable to sol...

In this paper, a generalization of the estimate local method named GELM is proposed in which a new semi analytical approach is presented to solve the free motion equation of a multi-span bridge. By the superposition of wavenumbers with the corresponding beam mode shape, the bi-dimensional equation of the plate which was used to model the roadway br...

Numerical models of periodically stiffened axisymmetric submerged shells impinged by an acoustic plane wave have been developed in order to study the scattered pressure by this target. Along with experimental results, they show that Bragg, Bloch-Floquet and helical waves can be observed. Nevertheless, the influence of added non-axisymmetric interna...

Abstract The irrotational part of the structural intensity for flexural wave motion in plate-like structures is calculated from measurement data of kinematic quantities, such as out-of-plane velocities, by a new method that makes use of a test functional series expansion. The computation of the structural intensity and its irrotational part, which...

A damage identification method named virtual vibration deflection (VVD) was developed, the principle of which was formulated based on the “weak” modality of the pseudo-excitation (PE) approach previously established. In essence, VVD is based on locating structural damage within a series of “sub-regions” divided from the entire structure under inspe...

Numerical methods are nowadays widely used to predict the vibroacoustic behavior of mechanical systems. Nevertheless, when the system is complex as for instance in the aerospace or naval industry, it is practically impossible to solve for the problem at once, more particularly at medium or high frequencies. That is why substructuring approaches hav...

This work aims at analyzing structures by mean of an inverse vibratory method consisting in an evolution of the Force Analysis Technique. The latter developed by Pézerat et al. firstly allowed localization and quantification of vibratory sources from measurement of the displacement field. In 2012 Ablitzer et al. improved the procedure for character...

Many methods to detect, quantify, or reconstruct acoustic sources exist in the literature and are widely used in industry (near-field acoustic holography, inverse boundary element method, etc.). However, the source identification in a reverberant or nonanechoic environment on an irregularly shaped structure is still an open issue. In this context,...

The acoustic detection of defects or leaks inside a cylindrical shell containing a fluid is of prime importance in the industry, particularly in the nuclear field. This paper examines the beamforming technique which is used to detect and locate the presence of an acoustic monopole inside a cylindrical elastic shell by measuring the external shell v...

Nowadays, the need of source identification methods is still growing and application cases are more and more complex. As a consequence, it is necessary to develop methods allowing us to reconstruct sound fields on irregularly shaped sources in reverberant or confined acoustic environment.
The inverse Patch Transfer Functions (iPTF) method is suitab...

This paper presents a method of determining an appropriate equation of motion of two-dimensional plane structures like membranes and plates from vibration response measurements. The local steady-state vibration field is used as input for the inverse problem that approximately determines the dispersion curve of the structure. This dispersion curve i...

A damage characterization framework based on the “pseudo-excitation” (PE) approach has recently been established, aimed at quantitatively identifying damage in beam-, plate-, and shell-like structural components. However, it is envisaged that the effectiveness of the PE approach can be restricted in practical implementation, due to the involvement...

Transient sonar detection systems have been developed over the last decades, and hence transient noise emissions from ship have become a matter of concern for acoustic discretion. One step towards the mitigation of transient noise emissions from ships consists in the accurate localization and identification of the noise sources. We use in this pape...

Numerical methods are nowadays widely used to predict the vibroacoustic behavior of mechanical systems. Nevertheless, when the system is complex as for instance in the aerospace or naval industry, it is practically impossible to solve for the problem at once, more particularly at medium or high frequencies. That is why sub-structuring approaches ha...

The identification of excitations on plates by an inverse method using local Finite Element modeling is studied. A dynamic condensation is proposed in order to eliminate Degrees Of Freedom not directly measurable like rotations. Before the condensation, the Craig–Bampton method can be optionally used to reduce the model (decrease of both computatio...

Transient sonar detection systems have been developed over the last decades, and hence transient noise emissions from ships have become a matter of concern for acoustic discretion. A step towards the mitigation of transient noise emissions consists in the accurate localization and identification of the noise sources. We propose in this paper to app...

While the structural-acoustic coupling between flexible structures and closed acoustic cavities has been extensively studied in the literature, the modeling of structures coupled through open cavities, especially connected in cascade, is still a challenging task for most of the existing methods. The possible presence of micro-perforated panels (MPP...

Modeling sound transmission among acoustic media through mixed separations, consisting of both rigid/flexible structures with apertures, is a challenging task. The coexistence of both structural and acoustic transmission paths through the same coupling surface adds system complexities, hampering the use of existing sub-structuring modeling techniqu...

De nos jours, les systèmes de détection acoustique utilisés dans la lutte sous-marine sont capables d’analyser les bruits transitoires. Il est donc nécessaire pour l’industriel de maitriser la discrétion acoustique dans ce domaine. Afin de définir une méthodologie qui permettra de spécifier des exigences sur les matériels sources de bruit transitoi...

This article presents the modeling of aM EMS microphone with an original architecture formed of mechanical structures moving in the plane of the substrate. On the contrary of most microphones generally constituted of an oscillating membrane, some transducers developed by the CEA-LETI with M&NEMS technology use micro beams moving in the plane of the...

Statistical modal Energy distribution Analysis (SmEdA) can be used to model a fluid-structure-problem based on modal information of the uncoupled-subsystems. Recently the method has been extended to include the effect of a dissipative treatment (i.e. damping or absorbing material). In this paper, SmEdA is tested on a steel plate with/without dampin...

Interfacial debonding in multilayered engineering structures can jeopardize the structural integrity without timely awareness. By reconstructing the distribution of interfacial forces and canvassing local perturbance to the structural dynamic equilibrium, an identification approach for interfacial debonding between different structural components w...

Measuring the vibro-acoustic response of structures subjected to a turbulent boundary layer (TBL) excitation in operating conditions remains an open issue for experimenters. Generally, in situ measurements, e.g. flight tests, underwater measurements and wind tunnel measurements are carried out, although they require expensive facilities. As an alte...

Statistical modal Energy distribution Analysis (SmEdA) can be used as an
alternative to Statistical Energy Analysis for describing subsystems with low
modal overlap. In its original form, SmEdA predicts the power flow exchanged
between the resonant modes of different subsystems. In the case of sound
transmission through a thin structure, it is well...

This paper describes the conception, designs consideration and fabrication process of a novel MEMS microphone. The presented microphone not only uses a new architecture, the sensitive part being beams moving within the plane of the substrate, but also uses an innovative detection means with Silicon piezo-resistive nanogauges. Modelization will cons...

The aim of this work consists in evaluating and analyzing vibrations and radiated pressure from a fluid loaded structure excited by a transient mechanical source. The time signature can be estimated from a discrete inverse Fourier transform of the Frequency Response Functions (FRF) of the considered system. In order to validate the numerical proces...

Energy methods like Statistical Energy Analysis (SEA) or Statistical modal Energy distribution Analysis (SmEdA), based on the well-known equations of two coupled oscillators, are both limited when non-resonant contributions of modes are not negligible (typically in the case of cavity/structure/cavity coupling). In SEA, this non-resonant contributio...

Previously, an inverse damage characterization framework was proposed by quantifying the perturbation to local dynamic equilibrium of a beam-like structure, showing advantages in some aspects over the traditional global vibration-based and local guided-wave-based methods. Residing on the plate theory, this framework was expanded to a two-dimensiona...

Vibroacoustic systems, involving cascade structures mutually coupled through partially open/close acoustic cavities, are commonly seen in various applications. The modeling of such systems is challenging since the two adjacent acoustic domains separated by the partial partition are connected both structurally and acoustically, where the continuity...

An additive damping treatment is an effective tool to control the dynamic response of built-up structures, and it is widely utilized through industrial applications. By applying a viscoelastic layer on a given structure, the vibratory energy is dissipated through shear and in-plane motions at the layer interface. Modeling the effect of such a treat...

Regarding to GEN 4 context, it is necessary to fulfil the high safety standards for sodium fast reactors (SFR), particularly against water-sodium reaction which may occur in the steam generator units (SGU) in case of leak. This reaction can cause severe damages in the component in a short time. Detecting such a leak by visual in-sodium inspection i...

The miniaturization of microphones is of great interest for several fields, such as medical applications (audio implants), or consumer electronics (cell phones). Almost all existing miniature microphones rely on electrostatic transduction and offer good performances (sensitivity, frequency bandwidth). However, their sensitivity, proportional to the...

Statistical modal Energy distribution Analysis (SmEdA) may be used as alternative to Statistical Energy Analysis for describing subsystems with low modal overlap. In its original form, SmEdA predicts the power flow exchanged between the resonant modes of different subsystems. In the case of the sound transmission through a thin light structure, it...

Statistical modal Energy distribution Analysis (SmEdA) may be used as alternative to Statistical Energy Analysis for describing subsystems with low modal overlap. In its original form, SmEdA predicts the power flow exchanged between the resonant modes of different subsystems. In the case of the sound transmission trough a thin light structure, it i...

This paper deal with the problem of model selection applied to the vibration. The goal of this research is to identify the most appropriate model (represented by its equation of motion) for given experimental measurements. This research is motivated by a necessity to describe the behaviour of structures whose model is either not known, or there may...

In this paper, we present a new simple and effective analytical approach to solve the equation of motion of an N-span bridge. By the superposition of wave numbers k1i with mode shapes corresponding to the beam modes, we found that it is possible to simplify the two-dimensional equation of the plate which was used as the road bridge model to a very...

The study of the dynamic behavior of the roadway bridges solicited by the mobile vehicles’ passage is a topicality subject, which interests many researchers in different fields. In this work, we present a roadway bridge modeling by the equation of motion of a multi span orthotropic thin plate. We propose to solve the free vibration equation by sepa...

Introduction Posing the problem: writing down boundary conditions Solution of the equation of motion by separation of variables Vibration modes of plates supported at two opposite edges Vibration modes of rectangular plates: approximation by the edge effect method Calculation of the free vibratory response following the application of initial condi...

Introduction Reference example: bending vibrations of beams Functional base of the finite elements type: application to longitudinal vibrations of beams Functional base of the modal type: application to plates equipped with heterogenities Elastic boundary conditions Convergence of the Rayleigh-Ritz method Conclusion

Objective of the chapter Stages of the calculation of response by modal decomposition Examples of calculation of generalized mass and stiffness Solution of the modal equation Example response calculation Convergence of modal series Conclusion

Introduction The problem Solution of the equation of the homogenous beam with a constant cross-section Propagation in infinite beams Introduction of boundary conditions: vibration modes Stress-displacement connection Influence of secondary effects Conclusion

Objective of the chapter Equations of motion and boundary conditions of continuous media Study of the vibrations: small movements around a position of static, stable equilibrium Conclusion