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See detailModal Analysis of a Nonlinear Periodic Structure with Cyclic Symmetry
Georgiades, Fostios; Peeters, Maxime ULg; Kerschen, Gaëtan ULg et al

in AIAA Journal (2009), 47

The objective of this paper is to examine nonlinear normal modes and their bifurcations in cyclic periodic structures. The nonlinear normal modes are computed using a numerical technique that combines ... [more ▼]

The objective of this paper is to examine nonlinear normal modes and their bifurcations in cyclic periodic structures. The nonlinear normal modes are computed using a numerical technique that combines shooting and pseudoarclength continuation. Unlike perturbation techniques, the resulting algorithm can investigate strongly nonlinear regimes of motion. This study reveals that modal interactions may occur without necessarily having commensurate natural frequencies in the underlying linear system. In addition, a countable infinity of such modal Q2 interactions are shown to exist in the system. [less ▲]

Detailed reference viewed: 39 (3 ULg)
See detailModal analysis of a nonlinear structure with cyclic symmetry
Peeters, Maxime ULg; Viguié, Régis ULg; Kerschen, Gaëtan ULg et al

in 27th International Modal Analysis Conference, Orlando, 2009 (2009)

Detailed reference viewed: 77 (21 ULg)
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See detailModal analysis of mineral blends using optical image analysis versus X ray diffraction
Bouzahzah, Hassan; Califice, Arnaud ULg; Benzaazoua, Mostafa et al

in GU, Ying; BUTCHER, Alan; STEELE, David (Eds.) Proceedings of International Congress for Applied Mineralogy ICAM08 (2008)

Detailed reference viewed: 143 (22 ULg)
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See detailModal Analysis of Nonlinear Vibrating Systems: Recent Progress and Challenges, KEYNOTE LECTURE
Kerschen, Gaëtan ULg

in Proceeedings of the Eighth European Conference on Structural Dynamics (2011)

Theoretical and experimental modal analysis, i.e., the computation of vibration modes from a mathematical model and from experimental data, respectively, is quite sophisticated and advanced in linear ... [more ▼]

Theoretical and experimental modal analysis, i.e., the computation of vibration modes from a mathematical model and from experimental data, respectively, is quite sophisticated and advanced in linear structural dynamics. However, nonlinearity is a frequent occurrence in real-world engineering structures, and the existing linear methodologies can no longer be used in this context. Therefore, the development of a nonlinear analog of modal analysis would be a timely contribution. Because nonlinear normal modes (NNMs) provide solid mathematical foundations for a rigorous analysis of nonlinear dynamical behaviors, a framework which includes both their computation from finite element models and their identification from experimental data is proposed in this paper. In view of the still limited use of NNMs in structural dynamics, special attention is devoted to develop tools that have the potential to deal with large-scale structures. [less ▲]

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See detailModal Analysis of Plate Structures Using Digital Speckle Pattern Interferometry
Slangen, Pierre; Lion, Yves; Golinval, Jean-Claude ULg et al

Conference given outside the academic context (1995)

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See detailModal identification and damage detection using the data-driven stochastic subspace and ARMAV methods
Bodeux, Jean-Bernard; Golinval, Jean-Claude ULg

in Mechanical Systems & Signal Processing (2003), 17(1), 83-89

This paper presents results of modal identification and damage detection on the Steel-Quake structure using the autoregressive moving average vector and data-driven stochastic subspace methods. The ... [more ▼]

This paper presents results of modal identification and damage detection on the Steel-Quake structure using the autoregressive moving average vector and data-driven stochastic subspace methods. The methods directly work with the recorded time signals and allow to analyse linear systems where only the system output is measured, while the input is unknown but produced by uncorrelated random signals. These techniques can also be used directly to analyse data obtained from the free response of linear systems. (C) 2003 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailModal identification in presence of noise using an optimization approach
Thonon, Carole; Golinval, Jean-Claude ULg

Conference given outside the academic context (2000)

This paper deals with the problem of modal parameter identification when the measurements are perturbed by unknown but bounded noise. It is well known that the classical Total Least Square (TLS) solution ... [more ▼]

This paper deals with the problem of modal parameter identification when the measurements are perturbed by unknown but bounded noise. It is well known that the classical Total Least Square (TLS) solution is the most accurate one, but that it is quite sensitive to data perturbations. This feature is a big drawback since it is desirable that the estimated modal parameters should not vary when perturbations on measurements change. An optimisation technique suited to so-called second-order cone programs [2] is proposed and tested. This method sets the identification problem in a MIN-MAX formulation [1] and uses an iterative interior-point primal-dual potential reduction algorithm [3, 4]. The residual error is first maximised over the set of possible perturbations leading thus to a worst-case residual error. Then, it is minimised over the set of identification variables. This procedure guarantees the robustness of the solution in the sense that no perturbation of the considered set could make the residual error bigger. This robustness is obtained to the detriment of an absolute accuracy. A good compromize between robustness and accuracy may be found through the prior resolution of the associate TLS problem. The optimisation program is tested in the case of a clamped-free beam for which closed-form solutions are available. A comparison with the TLS solution is also performed. [less ▲]

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See detailModal Identification of the "Steel-Quake" Structure Using the Data-Driven Stochastic Subspace and ARMAV Methods
BODEUX, Jean-Bernard; Golinval, Jean-Claude ULg

Conference given outside the academic context (2001)

In this paper, two techniques used for modal identification of output-only systems are presented and compared. The first technique is based on an ARMAV model. The method is known as the prediction error ... [more ▼]

In this paper, two techniques used for modal identification of output-only systems are presented and compared. The first technique is based on an ARMAV model. The method is known as the prediction error method (PEM) and requires a non-linear iterative optimisation procedure. The second technique is a stochastic subspace method that estimates the system matrices of a stochastic state space model by a data-driven algorithm and by using numerical techniques such as singular value and QR decompositions. The comparison between both techniques is performed over the “Steel-Quake” benchmark proposed in the framework of COST Action F3 “Structural Dynamics”. The results show that the investigated techniques give good results in term of estimated modal parameters. Especially, it is found that the stochastic subspace technique is much faster than the PEM. [less ▲]

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See detailModal identification of time-varying systems using simulated responses on wind turbines
Bertha, Mathieu ULg; Mayorga Rios, Jorge Patricio ULg; Golinval, Jean-Claude ULg

in Sas, P; Moens, D; Jonckheere, S (Eds.) Proceedings of ISMA2012-USD2012 (2012, September)

Wind turbines are good examples of time-varying systems as their modal properties depend on their instantaneous configuration. To catch the variations of modal parameters in time-varying systems ... [more ▼]

Wind turbines are good examples of time-varying systems as their modal properties depend on their instantaneous configuration. To catch the variations of modal parameters in time-varying systems, classical identification methods have to be adapted to the non-stationary nature of the recorded signals. In this paper, it is proposed to study the dynamic behavior of an offshore five-megawatt wind turbine. First, a numerical model of the wind turbine is created to serve as reference. Then, the time-varying behavior of the system is evaluated by simulating a large number of possible configurations. To this purpose, time responses are generated from the numerical model submitted to different environmental conditions. The wind is considered as the main non-measured external excitation force on the structure and the responses are recorded at several locations to simulate a real measurement process. Special care is brought to the accessibility of the measurement locations and to the limited number of available sensors in practice. Using these simulated measurements, output-only identification methods are used to extract varying dynamic properties of the structure. The final objective of this work is to pave the way to online condition monitoring of wind turbines. [less ▲]

Detailed reference viewed: 44 (14 ULg)
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See detailModal image analysis of metallic sulphides in core samples - a critical test of the methodology
Castroviejo, Ricardo; Lopez, Antonio; Muzquiz, Carlos et al

in Proceedings of GeoVision 99 (1999)

Detailed reference viewed: 10 (2 ULg)
See detailModal testing of non-linear vibrating structures
Peeters, Maxime ULg; Kerschen, Gaëtan ULg

in 11th European Conference on Spacecraft Structures, Materials and Mechanical Testing, Toulouse, 2009 (2009)

Detailed reference viewed: 9 (7 ULg)
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See detailModal testing of nonlinear vibrating structures based on a nonlinear extension of force appropriation
Peeters, Maxime ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in ASME International Design Engineering Technical Conferences, San Diego, 2009 (2009)

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See detailModal testing using nonlinear normal modes: experimental demonstration
Peeters, Maxime ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in Proceedings of the International Conference on Noise and Vibration Engineering (2010)

Modal testing and analysis is well-established for linear vibrating structures. While the common practice is to assume linear behavior, nonlinearity is a frequent occurrence in engineering applications ... [more ▼]

Modal testing and analysis is well-established for linear vibrating structures. While the common practice is to assume linear behavior, nonlinearity is a frequent occurrence in engineering applications and can drastically alter the behavior of mechanical systems. In this paper, an attempt is made to extend experimental modal analysis methodology to a practical nonlinear analog. In this context, nonlinear normal modes (NNMs) offer a solid theoretical and mathematical tool for interpreting a wide class of nonlinear dynamical phenomena, yet they have a clear and simple conceptual relation to the classical linear normal modes. Based on a nonlinear extension of phase resonance testing (also called force appropriation), the proposed methodology excites the structure to isolate one single NNM during the experiments. Thanks to the invariance principle, the energy dependence of that nonlinear mode (i.e., the NNM modal curves and their frequencies of oscillation) can be extracted from the resulting free decay response using time-frequency analysis. The proposed method is demonstrated using an experimental cantilever beam with a geometrical nonlinearity. [less ▲]

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See detailLa modalité en néo-égyptien
Polis, Stéphane ULg

Book published by Brill (in press)

Cette monographie est issue de ma thèse de doctorat qui constituait la première étude globale de la modalité en néo-égyptien. Le chapitre introductif [§1] est consacré à la définition du corpus néo ... [more ▼]

Cette monographie est issue de ma thèse de doctorat qui constituait la première étude globale de la modalité en néo-égyptien. Le chapitre introductif [§1] est consacré à la définition du corpus néo-égyptien et intègre une discussion des différentes formes de variation (diachronique, diatopique, diaphasique et diastratique) au sein du corpus néo-égyptien. Cet effort définitoire conforte l’assise empirique de l’étude : la ventilation du corpus en fonction de critères chronologiques et géographiques, de la nature du support et des genres littéraires permet d’objectiver les analyses proposées pour chaque expression de la modalité. Le corps du travail se divise en trois parties consacrées, respectivement, [§2] à une définition générale de la notion de modalité (devant permettre de déterminer les media expressifs qui relèvent de son étude en néo-égyptien) ainsi qu’à l’établissement d’un modèle sémantique de cette notion qui réponde aux impératifs d’économie ainsi que de cohérence et qui rende justice aux données typologiques ; [§3] à l’étude des modalités radicales (i.e. les modalités déontiques et bouliques), en envisageant les relations qu’elles entretiennent avec le domaine axiologique ; [§4] à l’examen des modalités assertives ([§4.a] analyse des formes de complémentation, en ce compris les liens entre intégration syntaxique, variation de l’assertivité et degrés de manipulation ; [§4.b] étude de l’impact des auxiliaires d’énonciation sur le degré d’assertivité d’une proposition ; [§4.c] critique des théories existantes concernant les moyens expressifs du discours indirect en néo-égyptien). Les conclusions [§5] sont accompagnées de propositions prospectives devant permettre [§5.a] de rendre le modèle défendu applicable pour l’étude des complexes conditionnels, [§5.b] d’intégrer la dimension énonciative dans l’analyse des relations interpersonnelles, [§5.c] de décrire adéquatement les expressions de la causalité et de la finalité. [less ▲]

Detailed reference viewed: 68 (11 ULg)
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See detailModalités d’interaction sur interface gestuelle : première évaluation des usages spontanés
Vandamme, Jean-François; Safin, Stéphane ULg; Leclercq, Pierre ULg

Conference (2007, November)

Detailed reference viewed: 78 (1 ULg)
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See detailModalités d'utilisation d'un abri par des taurillons au pâturage
Vandenheede, Marc ULg; Nicks, Baudouin ULg; Canart, Bernard et al

in Annales de Médecine Vétérinaire (1992), 136

Detailed reference viewed: 9 (1 ULg)