References of "Golinval, Jean-Claude"
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See detailVibration Mitigation of Nonlinear Vibrating Structures using Nonlinear Energy Sinks
Viguié, Régis ULg; Peeters, Maxime ULg; Kerschen, Gaëtan ULg et al

in 26th International Modal Analysis Conference, Orlando, 2008 (2008)

The tuned mass damper (TMD) is a simple and efficient device, but it is only effective when it is precisely tuned to the frequency of a vibration mode. Because nonlinear vibrating structures have resonant ... [more ▼]

The tuned mass damper (TMD) is a simple and efficient device, but it is only effective when it is precisely tuned to the frequency of a vibration mode. Because nonlinear vibrating structures have resonant frequencies that vary with the amount of total energy in the system, the efficiency of a TMD is questionable in this case. In the present study, the performance of an essentially nonlinear attachment, termed a nonlinear energy sink (NES), is assessed. It is shown that, unlike the TMD, an NES has no preferential resonant frequency, which makes it a good candidate for vibration mitigation of nonlinear vibrating structures. [less ▲]

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See detailComputation of Nonlinear Normal Modes using Numerical Continuation Techniques
Peeters, Maxime ULg; Viguié, Régis ULg; Serandour, Guillaume et al

in International Confernce on Advanced Computational Methods in Engineering, Liège, 2008 (2008)

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See detailOperational Modal Analysis using Second-Order Blind Identification
Poncelet, Fabien ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in 26th International Modal Analysis Conference, Orlando, 2008 (2008)

For modal analysis of large structures, it is unpractical and expensive to use artificial excitation (e.g., shakers). However, engineering structures are most often subject to ambient loads (e.g., traffic ... [more ▼]

For modal analysis of large structures, it is unpractical and expensive to use artificial excitation (e.g., shakers). However, engineering structures are most often subject to ambient loads (e.g., traffic and wind) that can be exploited for modal parameter estimation. One difficulty is that the actual loading conditions cannot generally be measured, and output-only measurements are available. This paper proposes to explore the utility of blind source separation (BSS) techniques for operational modal analysis. The basic idea of BSS is to recover unobserved source signals from their observed mixtures. The feasibility and practicality of the proposed method are demonstrated using an experimental application. [less ▲]

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See detailMEMS Modelling using Non-Conforming Elements
Rochus, Véronique ULg; Rixen, Daniel; Golinval, Jean-Claude ULg

(2008)

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See detailNonlinear Normal Modes, Part II: Practical Computation using Numerical Continuation Techniques
Peeters, Maxime ULg; Viguié, Régis ULg; Sérandour, Guillaume et al

in 26th International Modal Analysis Conference, Orlando, 2008 (2008)

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companion, Part I. One reason of the still limited use of NNMs in structural dynamics is that their computation is ... [more ▼]

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companion, Part I. One reason of the still limited use of NNMs in structural dynamics is that their computation is often regarded as impractical. However, when resorting to numerical algorithms, we show that the NNM computation is possible with limited implementation effort, which paves the way to a practical method for determining the NNMs of nonlinear mechanical systems. The proposed algorithm relies on two main techniques, namely a shooting procedure and a method for the continuation of NNM motions. The algorithm is demonstrated using two different mechanical systems, a nonlinear two-degree-of-freedom system and a nonlinear cantilever beam discretized by the finite element method. [less ▲]

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See detailIn-orbit vibration testing of spacecraft structures
Poncelet, Fabien ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in International Conference on Noise and Vibration Engineering, Leuven, 2008 (2008)

In-orbit modal testing can be an interesting tool for the monitoring of spacecraft structures. In these applications, it is impossible to measure or to control the excitation resulting, for instance, from ... [more ▼]

In-orbit modal testing can be an interesting tool for the monitoring of spacecraft structures. In these applications, it is impossible to measure or to control the excitation resulting, for instance, from an impact with a small asteroid or from the working engines. Consequently the only realistic methodology must be an outputonly modal analysis, also called Operational Modal Analysis (OMA). This paper proposes another way of doing OMA where the post-processing (i.e. the physical modal parameter extraction) is simplified and automated. The methodology uses the Blind Source Separation (BSS) techniques which attempt to recover the source signals only from their observed mixtures. In case of structural dynamic responses, the source signals and the mixing matrix are equivalent to the modal coordinates and the mode matrix, respectively. The paper describes the complete methodology including the post-processing, and its feasibility is demonstrated using a numerical application modeling a truss satellite with the FE method. [less ▲]

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See detailModel of electrostatic actuated deformable mirror using strongly coupled electro-mechanical finite element
Rochus, Véronique ULg; Golinval, Jean-Claude ULg; Mendez, C. et al

in Analog Integrated Circuits and Signal Processing (2007), 53(2-3), 129-135

The aim of this paper is to deal with multi-physics simulation of micro-electro-mechanical systems (MEMS) based on an advanced numerical methodology. MEMS are very small devices in which electric as well ... [more ▼]

The aim of this paper is to deal with multi-physics simulation of micro-electro-mechanical systems (MEMS) based on an advanced numerical methodology. MEMS are very small devices in which electric as well as mechanical and fluid phenomena appear and interact. Because of their microscopic scale, strong coupling effects arise between the different physical fields, and some forces, which were negligible at macroscopic scale, have to be taken into account. In order to accurately design such micro-electro-mechanical systems, it is of primary importance to be able to handle the strong coupling between the electric and the mechanical fields. In this paper, the finite element method (FEM) is used to model the strong coupled electro-mechanical interactions and to perform static and transient analyses taking into account large mesh displacements. These analyses will be used to study the behaviour of electrostatically actuated micro-mirrors. [less ▲]

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See detailLOCALIZATION OF ENERGY IN A PERFECTLY SYMMETRIC BLADED DISK ASSEMBLY DUE TO NONLINEARITIES
Georgiades, Fotios; Peeters, Maxime ULg; Kerschen, Gaëtan ULg et al

in ASME Internaional Mechanical Engineering Congress and Exposition, Seattle, 2007 (2007, November)

Although a bladed disk is typically designed to have identical blades, manufacturing tolerances, wear, and other causes may cause random deviations among the blades. The blade-to-blade discrepancies ... [more ▼]

Although a bladed disk is typically designed to have identical blades, manufacturing tolerances, wear, and other causes may cause random deviations among the blades. The blade-to-blade discrepancies, denoted as mistuning, lead to vibratory responses mostly concentrated in small regions of the bladed-disk assembly, according to a phenomenon called localization. The resulting spatial confinement of the vibration energy causes the responses of some blades to become dangerously high and increases the amplitude of the bladed-disk assembly's overall response. The attendant increase in stresses can lead to premature high cycle fatigue (HCF) of the blades. In this study we investigate whether vibration localization in a perfectly symmetric bladed disk assembly may occur in the presence of nonlinearity. To this end, the nonlinear normal modes (NNMs) of a simplified model of a bladed disk assembly are computed. The NNMs are then carefully examined to highlight possible vibration localization phenomena. [less ▲]

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See detailNon-conforming element for accurate modelling of MEMS
Rochus, Véronique ULg; Rixen, Daniel J.; Golinval, Jean-Claude ULg

in Finite Elements in Analysis & Design (2007), 43(10), 749-756

In this work different modelling techniques are investigated to simulate the dynamic behaviour of slender structures on which electrostatic forces are acting. In particular, non-conforming elements are ... [more ▼]

In this work different modelling techniques are investigated to simulate the dynamic behaviour of slender structures on which electrostatic forces are acting. In particular, non-conforming elements are tested to model micro- mechanical devices (or MEMS) having a very large aspect ratio. These elements are constructed on linear shape functions enriched by internal second-order polynomials. As a consequence the element compatibility is not exactly satisfied, but such elements can efficiently model beam- or shell-like structures with a small number of degrees of freedom. The advantage of non-conforming elements compared to shell or beam elements is that they are volume elements and can therefore easily be combined with other volume finite elements. For micro-mechanical systems the structure must be coupled to the electrostatic domain with the so-called electro-mechanical elements that solve for the electrostatic potential and generate the electrostatic forces. This paper shows that constructing coupled electro-mechanical models for high aspect ratio systems is then greatly simplified when non-conforming finite elements are used. The theory is presented for small deformations and also for large displacements where geometric non-linearities must be accounted for. The elements proposed in this paper are based on non-conforming formulations published earlier. The efficiency of the non-conforming approach combined with specific electro-mechanical elements is highlighted in the analysis of two simple MEMS for which the pull-in voltage is computed. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailTopology optimization of microbeams including layer deposition manufacturing constraints
Lemaire, Etienne ULg; Rochus, Véronique; Fleury, Claude et al

Conference (2007, May)

As many manufacturing techniques, microfabrication methods possess limitations. Consequently, manufacturing constraints have to be considered during microsystems design process. Therefore, the direct use ... [more ▼]

As many manufacturing techniques, microfabrication methods possess limitations. Consequently, manufacturing constraints have to be considered during microsystems design process. Therefore, the direct use of automatic design tools like topology optimization is not possible. For instance, optimal topologies generally contain closed cavities that cannot be produced using the usual microfabrication techniques like layer deposition. The present paper intends to add a layer deposition constraint to the optimization problem using recent developments of CONLIN software. However, with this new optimization procedure we could observe that classical sensitivities filtering makes optimization problem rather unstable while filtering the density field itself keeps good convergence properties. [less ▲]

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See detailIdentification of Linear and Nonlinear Systems using Signal Processing Techniques
Kerschen, Gaëtan ULg; Poncelet, Fabien ULg; Golinval, Jean-Claude ULg et al

in 26th Benelux Meeting on Systems and Control, Lommel, 2007 (2007)

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See detailPhysical interpretation of independent component analysis in structural dynamics
Kerschen, Gaëtan ULg; Poncelet, Fabien ULg; Golinval, Jean-Claude ULg

in Mechanical Systems & Signal Processing (2007), 21

This paper focuses on the relation between the vibration modes of mechanical systems and the modes computed through a blind source separation technique called independent component analysis (ICA). For ... [more ▼]

This paper focuses on the relation between the vibration modes of mechanical systems and the modes computed through a blind source separation technique called independent component analysis (ICA). For free and random vibrations of weakly damped systems, a one-to-one relationship between the vibration modes and the ICA modes is demonstrated using the concept of virtual source. Based on this theoretical link, a time-domain structural system identification technique is proposed and is illustrated using numerical examples. [less ▲]

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See detailThe global modal parameterization for non-linear model-order reduction in flexible multibody dynamics
Bruls, Olivier ULg; Duysinx, Pierre ULg; Golinval, Jean-Claude ULg

in International Journal for Numerical Methods in Engineering (2007), 69(5), 948-977

In flexible multibody dynamics, advanced modelling methods lead to high-order non-linear differential-algebraic equations (DAEs). The development of model reduction techniques is motivated by control ... [more ▼]

In flexible multibody dynamics, advanced modelling methods lead to high-order non-linear differential-algebraic equations (DAEs). The development of model reduction techniques is motivated by control design problems, for which compact ordinary differential equations (ODEs) in closed-form are desirable. In a linear framework, reduction techniques classically rely on a projection of the dynamics onto a linear subspace. In flexible multibody dynamics, we propose to project the dynamics onto a submanifold of the configuration space, which allows to eliminate the non-linear holonomic constraints and to preserve the Lagrangian structure. The construction of this submanifold follows from the definition of a global modal parameterization (GMP): the motion of the assembled mechanism is described in terms of rigid and flexible modes, which are configuration-dependent. The numerical reduction procedure is presented, and an approximation strategy is also implemented in order to build a closed-form expression of the reduced model in the configuration space. Numerical and experimental results illustrate the relevance of this approach. Copyright (c) 2006 John Wiley [less ▲]

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See detailOutput-only modal analysis using blind source separation techniques
Poncelet, Fabien ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg et al

in Mechanical Systems & Signal Processing (2007), 21(6), 2335-2358

The present study carries out output-only modal analysis using two blind source separation (BSS) techniques, namely independent component analysis and second-order blind identification. The concept of ... [more ▼]

The present study carries out output-only modal analysis using two blind source separation (BSS) techniques, namely independent component analysis and second-order blind identification. The concept of virtual source is exploited and renders the application of these BSS techniques possible. The proposed modal analysis method is illustrated using numerical and experimental examples. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailUsing Targeted Energy Transfer to Stabilize Drill-string Systems
Viguié, Régis ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg et al

in 25th International Modal Analysis Conference, Orlando, 2007 (2007)

Torsional vibration of the drill strings used in drilling oil and gas wells arises from a complex interaction of the dynamics of the drilling structure with speed-dependent effective rock-cutting forces ... [more ▼]

Torsional vibration of the drill strings used in drilling oil and gas wells arises from a complex interaction of the dynamics of the drilling structure with speed-dependent effective rock-cutting forces. These forces are often difficult to model, and contribute substantially to the problems of controlling the drilling operation so as to produce steady cutting. We consider here the use of a nonlinear energy sink (NES) , an attachment which has been shown to be effective in reducing or even eliminating self-excited motions in van der Pol and aeroelastic systems. The NES is a completely passive, inherently broadband vibration absorber capable of attracting and dissipating vibrational energy from primary structures, in this case nonlinear discontinuous models of drill-string systems. In this paper we describe a prototypical drill string-NES system, briefly discuss some of the analytical and computational tools suitable for its analysis, and then concentrate on mathematical results on the efficacy of the NES in this application and their physical Interpretation. [less ▲]

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See detailBLIND SOURCE SEPARATION TECHNIQUES FOR MODAL ANALYSIS: EXPERIMENTAL DEMONSTRATION
Poncelet, Fabien ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg et al

in International Conference on Engineering Dynamics, Carvoeiro, 2007 (2007)

The present study carries out output-only modal analysis using two blind source separation (BSS) techniques, namely independent component analysis and second-order based identification. It is shown under ... [more ▼]

The present study carries out output-only modal analysis using two blind source separation (BSS) techniques, namely independent component analysis and second-order based identification. It is shown under which circumstances the normal coordinates of the vibration modes may be interpreted as virtual sources, which renders the application of these BSS techniques possible. To support the theoretical findings, numerical experiments are first carried out using a discrete system of three masses. Secondly the method is applied to a real-life structure which is a blade extracted from a turbojet engine stator. The results are compared with the stochastic subspace identification method. [less ▲]

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See detailBlind source separation techniques - Another way of doing operational modal analysis
Poncelet, Fabien ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg et al

in International Operational Modal Analysis Conference, Copenhague, 2007 (2007)

In many practical applications, it is difficult or even impossible to measure the force applied to a structure. This is especially the case in civil engineering applications. Therefore, this paper ... [more ▼]

In many practical applications, it is difficult or even impossible to measure the force applied to a structure. This is especially the case in civil engineering applications. Therefore, this paper proposes to explore the utility of blind source separation (BSS) techniques for operational modal analysis. The basic idea of BSS is to recover unobserved source signals from their observed mixtures. The feasibility and practicality of the proposed method are demonstrated using an experimental application. [less ▲]

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See detailPractical Computation of Nonlinear Normal Modes Using Numerical Continuation Techniques
Peeters, Maxime ULg; Viguié, Régis ULg; Kerschen, Gaëtan ULg et al

in International Workshop: Advancements in Design Optimization of Materials, Structures and Mechanical Systems, Xi'An, 2007 (2007)

The concept of nonlinear normal modes (NNMs) is considered in the present paper. One reason of the still limited use of NNMs in structural dynamics is that their computation is often regarded as ... [more ▼]

The concept of nonlinear normal modes (NNMs) is considered in the present paper. One reason of the still limited use of NNMs in structural dynamics is that their computation is often regarded as impractical. However, when resorting to numerical algorithms, we show that the NNM computation is possible with limited implementation effort, which paves the way to a practical method for determining the NNMs of nonlinear mechanical systems. The proposed algorithm relies on two main techniques, namely a shooting procedure and a method for the continuation of NNM motions. The algorithm is demonstrated using two different mechanical systems, a nonlinear two-degree-of-freedom system and a nonlinear cantilever beam discretized by the finite element method. [less ▲]

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See detailPARTICIPATION OF ULG STUDENTS TO THE SSETI MICROSATELLITE PROGRAMME USING SAMCEF
Bolland, M.; COLLIGNON, G.; VANDENPLAS, X. et al

Conference (2007)

The objective of this presentation is to discuss the participation of students at the University of Liège to the educational spacecraft project SSETI-ESEO proposed by the European Space Agency. SSETI ... [more ▼]

The objective of this presentation is to discuss the participation of students at the University of Liège to the educational spacecraft project SSETI-ESEO proposed by the European Space Agency. SSETI students are now mainly involved in the ESEO satellite for which the University of Liège is in charge of the MECH work package. The students have to propose a design for the structure of the solar panels (including the geometry and materials) and their deployment and pointing mechanisms (including electrical circuits, motors, hinges and actuators). Through detailed finite element computations in the SAMCEF software, they have to verify the structural integrity of the panels during the launch phase and to guarantee a safe deployment once on-orbit. Another task is to ensure an appropriate orientation of the solar panels to collect the maximum power from the sun. An industrial partner specialized in the development of computer-aided engineering solutions, SAMTECH, and a research center, Liège Space Center (CSL), also bring their expertise to the project. [less ▲]

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