Papers by Emmanuel FOLTETE
Journal of Sound and Vibration, 2015
This document is the author's final manuscript of M. Ouisse, E. Foltête: Model correlation and id... more This document is the author's final manuscript of M. Ouisse, E. Foltête: Model correlation and identification of experimental reduced models in vibroacoustical modal analysis. Journal of Sound and Vibration 342 (2015) 200-217.
The Journal of the Acoustical Society of America, 2008
The localization of noise sources from a specified direction may often be accomplished with an ar... more The localization of noise sources from a specified direction may often be accomplished with an array of sensors. One commonly used processor consists of delay and add networks: a conventional beamformer, however its spectrum suffers from the Rayleigh resolution and its performance is highly degraded, specially in lower frequency range. In the communication, the performance of some typical high-resolution sensor array processing algorithms: Minimum Variance and MUSIC algorithms are investigated for wideband source location. Their performances are compared with a new source localization algorithm which is based on a sparse representation of sensor measurements with an overcomplete basis composed of samples from the array manifold. The key of the method is the use of the SVD for data reduction and the formulation of a joint multiplesample sparse representation problem in the signal subspace domain. Increased resolution and improved robustness to noise is obtained. Numerical examples are presented.
The Journal of the Acoustical Society of America, 2008
The classical u-p formulation for vibro-acoustic problems is very convenient for experimental vib... more The classical u-p formulation for vibro-acoustic problems is very convenient for experimental vibroacoustic modal analysis since the physical variables are directly those which are measured by operators. In this particular context, the objective is to identify from experimental measurements a reduced model which has the same behaviour as the measured one. The complex mode shapes which are identified using this technique must satisfy a properness condition. When they do not verify it, they should be modified to be able to represent the behaviour of a physical system. Some techniques have been proposed in order to develop a strategy to obtain the modified eigenshapes, but this is a quite difficult point because of the unsymmetric topology of the equations. In this paper, a symmetric formulation is used in order to be able to directly apply the classical methodology which has been developed for structural modal analysis to obtain the physical reduced system. The methodology is described and compared with the u-p formulation, in terms of efficiency and precision, in particular when some absorbing devices are considered. All results are first presented on an ideal numerical test-case, and applications on experimental data are finally shown.
Revue européenne de mécanique numérique, 2011
2007 IEEE Ultrasonics Symposium Proceedings, 2007
Energy scavenging research shows a growing interest these last years. This paper aims to demonstr... more Energy scavenging research shows a growing interest these last years. This paper aims to demonstrate the ability of micromachined vibrating structures to store mechanical energy and then to convert it into electrical energy through a piezoelectric plate. Such a micro power generator may be used as a mechanical to electrical energy transformer. The energy conversion consists in a mechanical shock enabling to convert low vibrating energy levels at very low frequencies (typically below 10 Hz for human being excitation source) to mechanical energy to the vibrating structure for which resonant frequencies are ranging from 10 kHz to 1 MHz. Moreover this basic low frequencies to high frequencies spectrum conversion enables to avoid frequency tuning designing that is required for adapting the frequency spectrum of the excitation source.
2007 IEEE Ultrasonics Symposium Proceedings, 2007
The design of mechanical systems requires various studies in order to ensure an optimal behavior ... more The design of mechanical systems requires various studies in order to ensure an optimal behavior during operation. In particular, the study of its dynamic behavior makes it possible to evaluate the role of a connection in the energy dissipation mechanisms. In this context, an experimental setup dedicated to small structures has been developed to quantify damping due to microsliding at the beam-clamp interface. The mechanical characterization of the clamped connection is carried out by experimental dynamic tests on a free-clamped structure. The instantaneous frequencies and damping are identified by the wavelet transform technique of a slightly non-linear system. In parallel, numerical prediction of the equivalent damping is achieved thanks to the implementation of the regularized Coulomb law in a finite element model. A genetic algorithm and artificial neural networks are used to update the stiffness parameter and the friction coefficient. The optimized model is in good agreement with experimental results. It allows for determining the spatial distribution of microsliding and tangential force along the contact interface. The dissipated energy and equivalent damping are finally deduced according to the dynamic deflection of the free part of the beam.
IEEE Ultrasonics Symposium, 2005., 2005
Energy scavenging research shows a growing interest these last years. This paper aims to demonstr... more Energy scavenging research shows a growing interest these last years. This paper aims to demonstrate the ability of micromachined vibrating structures to store mechanical energy and then to convert it into electrical energy through a piezoelectric plate. Such a micro power generator may be used as a mechanical to electrical energy transformer. The energy conversion consists in a mechanical shock enabling to convert low vibrating energy levels at very low frequencies (typically below 10 Hz for human being excitation source) to mechanical energy to the vibrating structure for which resonant frequencies are ranging from 10 kHz to 1 MHz. Moreover this basic low frequencies to high frequencies spectrum conversion enables to avoid frequency tuning designing that is required for adapting the frequency spectrum of the excitation source.
Conference Proceedings of the Society for Experimental Mechanics Series, 2013
The present paper addresses the experimental identification of a simplified realisation of a sola... more The present paper addresses the experimental identification of a simplified realisation of a solar array structure in folded configuration. To this end, a nonlinear subspace identification technique formulated in the frequency domain, referred to as the FNSI method, is exploited. The frequency response functions of the underlying linear structure and the nonlinear coefficients are estimated by this approach. Nonlinearity is caused by impacts between adjacent panels and friction and gaps appearing in their clamping interfaces. This application is challenging for several reasons, which include high modal density and the complicated nature of the involved nonlinear mechanisms.
Conference Proceedings of the Society for Experimental Mechanics Series, 2014
International Journal of Non-Linear Mechanics, 2014
Most identification methods in nonlinear structural dynamics assume in advance a mathematical mod... more Most identification methods in nonlinear structural dynamics assume in advance a mathematical model of the nonlinearities. This is however possible in specific situations only, since nonlinear effects may be caused by numerous phenomena and a priori knowledge is generally limited. The present paper investigates the usefulness of piecewise third-order polynomials, termed cubic splines, to identify the complex nonlinear dynamics of solar arrays in their stowed configuration. The estimation of the model parameters is achieved using the frequency-domain nonlinear subspace identification (FNSI) method. A distinct advantage of the FNSI approach is its capability to calculate accurately a large number of parameters, while maintaining an acceptable computational burden. This makes tractable the use of cubic splines to represent nonlinearity in real-life mechanical systems, as the dimensionality of the inverse problem is known to increase dramatically in this case. The experimental structure of interest consists of two parallel aluminium plates assembled with bolted connections. This application is challenging because of the existence of impacts between the two plates at high excitation amplitude, and of the activation of complicated stiffness and damping mechanisms within the bolted connections.
Smart Materials & Structures, 2007
Shape Memory Alloys (SMAs) are good candidates for being used as passive dampers, strain sensor, ... more Shape Memory Alloys (SMAs) are good candidates for being used as passive dampers, strain sensor, stiffness or shape driver. In order to develop the use of these alloys in structural vibration control, we present in this paper how we have implemented a phenomenological model based on the R l model in COMSOL which allow building automatically many loading cases in force or displacement. We use this implementation to simulate internal loops in order to characterize the stiffness and the damping effect by an Equivalent Complex Young's Modulus approach under a static strain offset. Thus, this study shows the influence of a static strain offset and the strain amplitude of vibration on the damping effect and the stiffness.
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
Following a campaign of structural dynamic measurements on an industrial structure, the question ... more Following a campaign of structural dynamic measurements on an industrial structure, the question often arises: “Is my structure non-linear?”. A response to this question is important to the extent that the presence of a nonlinearity, even local, can significantly affect the global dynamic behavior of a structure. Several techniques that enable engineers to detect a non-linear behavior can be found
Conference Proceedings of the Society for Experimental Mechanics Series, 2012
ABSTRACT
Journal of Sound and Vibration, 2015
ABSTRACT This study is related to structural vibration transmission at low frequencies and aims t... more ABSTRACT This study is related to structural vibration transmission at low frequencies and aims to propose a new approach to dynamically characterize the interface between different substructures of a complex coupled structure. A power flow mode method based on the imaginary part of the dynamic flexibility matrix is presented, which allows determining eigenvalues and eigenvectors representing qualitative and quantitative information on the power flowing inside the structure, respectively. It is further applied to study the power transmitted at the interface, making it possible to identify the direction associated to the dominant power flow patterns and to quantify their contributions. Specific properties dealing with moment excitation and mid-frequency approximation are also detailed to provide complementary insights into their dynamic meaning and behavior.
Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation, 2013
Heat transfer simulation within heating furnaces is of great significance for prediction and cont... more Heat transfer simulation within heating furnaces is of great significance for prediction and control of the performance of furnaces. In this paper, a set of models is proposed to solve heat transfer problems in a loaded furnace. Furthermore, a 2-dimensional algorithm based on a finite difference method is presented. The heat transfer models are integrated with a furnace model to simulate the heating process of workpieces. Temperature variation of the workpiece with time is predicted by the system. An experiment is carried out for validation of the system. The main objective of this work is to evaluate the behavior of a heated enclosure, when variable radiant panels are introduced. Experimental investigation shows that their efficiency depends on their position.
Condition Monitoring of Machinery in Non-Stationary Operations, 2012
Condition Monitoring of Machinery in Non-Stationary Operations, 2012
Conference Proceedings of the Society for Experimental Mechanics Series, 2014
Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring; Keynote Presentation, 2014
The shape memory polymers (SMPs) are polymeric smart materials which have the remarkable ability ... more The shape memory polymers (SMPs) are polymeric smart materials which have the remarkable ability to recover their primary shape from a temporary one under an external stimulus. The study deals with the synthesis and the thermomechanical characterization of a thermally-actuated SMP, the tBA/PEGDMA, with a special focus on viscoelastic properties. The mechanical characterization is performed using three kinds of tests: quasi-static tensile tests, dynamic mechanical analysis (DMA) and modal tests. The first one allows the identification of the Youngs modulus and the Poisson's ratio at ambient temperature. Modal analyses are done for various temperature values, and resonance frequencies are measured. In order to validate the time-temperature equivalence on this SMP, a DMA is performed under harmonic loading for different temperatures and a master curve highlights a complementarity of the results. Finally a suitable model for the viscoelastic behavior of the SMP is identified.
Mécanique & Industries, 2010
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Papers by Emmanuel FOLTETE