References of "Kerschen, Gaëtan"
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See detailDesign of the on-board computer of OUFTI-1 CubeSat
De Dijcker, S.; Crosset, N.; Verly, Jacques ULg et al

Conference (2011)

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See detailCubeSat Activities at the University of Liège
Denis, Amandine ULg; Pisane, Jonathan ULg; Verly, Jacques ULg et al

Conference (2011)

Detailed reference viewed: 23 (6 ULg)
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See detailInvestigating the performance of model order reduction techniques for nonlinear radiative heat transfer problems
Hickey, D.; Masset, Luc ULg; Kerschen, Gaëtan ULg et al

in Proceedings of the International Conference on Advanced Computational Methods in Engineering (2011)

The problem of nonlinear radiative heat transfer is one of great importance to the aerospace industry. However, analysing large-scale, nonlinear, multiphysical, dynamical structures, by using mathematical ... [more ▼]

The problem of nonlinear radiative heat transfer is one of great importance to the aerospace industry. However, analysing large-scale, nonlinear, multiphysical, dynamical structures, by using mathematical modelling and simulation, e.g. Finite Element Modelling (FEM), can be computationally expensive. This provides motivation for the development of Model-Order Reduction (MOR) techniques capable of reducing simulation times without the loss of important information. The objective is to demonstrate the method of Proper Orthogonal Decompostition (POD) as a technique for nonlinear MOR. The nonlinear radiative exchanges between a linear benchmark beam within an external box (Figure 1) are analysed and a reduction procedure for this fully coupled, nonlinear, multiphysical, thermomechanical system is established. The solution to the strongly coupled, thermomechanical equations of motion is found by making use of an extended version of the implicit generalized-alpha scheme. In the reduced model, the residual of the unreduced system of equations need to be evaluated at each Newton iteration of each time step. In order to optimise the efficiency of the reduction method it is shown that the internal forces can be split into their linear and nonlinear counterparts. Only the nonlinear terms change at each time step, thus only these terms need to remain in the iterative loop significantly reducing the number of parameters that are to be computed at each step. These efficiency improvements to the method are discussed and the results are given. [less ▲]

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See detailFinite Element Computation of Nonlinear Normal Modes
Renson, Ludovic ULg; Deliège, Geoffrey ULg; Noels, Ludovic ULg et al

in Fifth International Conference on Advanced COmputational Methods in ENgineering (2011)

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See detailDetection and quantification of non-linear structural behavior using principal component analysis
Hot, A.; Kerschen, Gaëtan ULg; Foltete, E. et al

in Mechanical Systems & Signal Processing (2011), 26

The detection of non-linear behavior in structural dynamics is a very important step to the extent that the presence of non-linearities, even local, can affect the global dynamic behavior of a structure ... [more ▼]

The detection of non-linear behavior in structural dynamics is a very important step to the extent that the presence of non-linearities, even local, can affect the global dynamic behavior of a structure. A large number of techniques that enable engineers to detect non-linear behavior can be found in the literature but most of these methods exploit frequency domain data and give better results with a stepped-sine excitation. The goal of this paper is to propose an alternative methodology that is based on the principal component analysis and uses time responses obtained with a random excitation. Two criteria will be used to quantify the difference between two response subspaces, based on the angle between them and the residual error resulting from the projection of one on the other. The concept of limit of linearity and design decision margins is also addressed in this paper. The methodology is demonstrated using an academic simulated system and then using measured data of a simplified solar array system. [less ▲]

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See detailVandalism Prevention of a Footbridge with Cable Vibrations
Canor, Thomas ULg; Kerschen, Gaëtan ULg; Denoël, Vincent ULg

in Biliszczuk, Jan; Bien, Jan; Hawryszkow, Pawel (Eds.) et al 4th International Conference Footbridge : Attractive structures at reasonable costs, Wroclaw 6-8 July 2011 (2011)

This work studies an unusual way to improve comfort of a footbridge with cables. Cables can be seen as a means of dissipating energy in a structure. This complementary source of dissipation does not ... [more ▼]

This work studies an unusual way to improve comfort of a footbridge with cables. Cables can be seen as a means of dissipating energy in a structure. This complementary source of dissipation does not prohibit resonance from taking place, but it is a way to limit vibrations and to impede vandals’ actions. This study is illustrated with measurements realized on a specific footbridge. This structure is a metallic arch characterized by a first natural frequency of 3.2Hz and a corresponding damping ratio of 0.55%. Intolerable accelerations (around 6m/s²) are easily reached when an ill-intentioned person is bouncing at an appropriate frequency. After installation of a single cable at a suitable location in the structure, the measured damping ratios are almost doubled and the maximum accelerations at resonance are reduced by 30%. With three cables on the footbridge, the damping ratio becomes significantly nonlinear: it reaches up to 3% for low amplitude oscillations, but drops down to 1% for moderate to high amplitudes. For higher accelerations, it does not seem to depend on the number of cables. According to these observations, a notable effect of cables is to reduce the maximum acceleration, but the main effect is to prolong the transient phase and to make the resonance frequency hardly identifiable by vandals. [less ▲]

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See detailNonlinear Normal Modes of a Full-Scale Aircraft
Peeters, Maxime ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg et al

in 29th International Modal Analysis Conference, Jacksonville, 2011 (2011)

Detailed reference viewed: 33 (2 ULg)
See detailContract 21539/08/NL/SFe - Advancement of mechanical verification methods for non-linear spacecraft: Nonlinearity identification methods: predictive analyses
Kerschen, Gaëtan ULg; Noël, Jean-Philippe ULg

Report (2010)

The objective of this technical note is to explore the applicability of nonlinear system identification techniques to spacecraft structures. To this end, numerical experiments carried out using the finite ... [more ▼]

The objective of this technical note is to explore the applicability of nonlinear system identification techniques to spacecraft structures. To this end, numerical experiments carried out using the finite element model of the SmallSat spacecraft are used, without, however, having access to the model itself. The constraints imposed by the considered techniques for breadboard testing are also highlighted. [less ▲]

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See detailModel order reduction techniques for thermomechanical systems with nonlinear radiative heat transfer using proper orthogonal decomposition
Hickey, Daryl ULg; Hoffait, Sébastien ULg; Rothkegel Ide, José Ignacio ULg et al

in Proceedings of ISMA 2010 (2010, September)

Analysing large scale, nonlinear, multiphysical, dynamical structures, by using mathematical modelling and simulation, e.g. Finite Element Modelling (FEM), can be computationally very expensive ... [more ▼]

Analysing large scale, nonlinear, multiphysical, dynamical structures, by using mathematical modelling and simulation, e.g. Finite Element Modelling (FEM), can be computationally very expensive, especially if the number of degrees-of-freedom is high. This paper develops modal reduction techniques for such nonlinear multiphysical systems. The paper focuses on Proper Orthogonal Decomposition (POD), a multivariate statistical method that obtains a compact representation of a data set by reducing a large number of interdependent variables to a much smaller number of uncorrelated variables. A fully coupled, thermomechanical model consisting of a multilayered, cantilever beam is described and analysed. This linear benchmark beam is then extended to incorporate an external box. The nonlinear radiative exchanges between the beam and the external box are analysed and a reduction procedure is proposed for this fully coupled, nonlinear, multiphysical, thermomechanical system. Two alternative approaches to the reduction are investigated, a monolithic scaled approach and a partitioned approach that treats the individual physical modes separately. [less ▲]

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See detailTheoretical and experimental modal analysis of nonlinear aerospace structures
Peeters, Maxime ULg; Golinval, Jean-Claude ULg; Kerschen, Gaëtan ULg

in Proceedings of the AIAA Modeling and Simulation Technologies Conference (2010)

Because nonlinearity is a frequent occurrence in aerospace applications, there is a need for e cient analysis procedures. In this context, nonlinear normal modes (NNMs) o er a solid mathematical tool for ... [more ▼]

Because nonlinearity is a frequent occurrence in aerospace applications, there is a need for e cient analysis procedures. In this context, nonlinear normal modes (NNMs) o er a solid mathematical tool for interpreting a wide class of nonlinear dynamical phenomena. The objective of this study is to highlight the usefulness of NNMs for modeling and testing of nonlinear aerospace structures. Both theoretical and experimental modal analysis are described and are illustrated. [less ▲]

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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 detailOrbital dynamics characteristics of a QB50 CubeSat performing atmospheric reentry
Asma, C.; Naviaux, J.; Kerschen, Gaëtan ULg et al

in Proceedings of the AIAA Atmospheric Flight Mechanics Conference (2010)

The QB50 mission has the scientific objective to study the temporal and spatial variations of a number of key parameters in the lower thermosphere with a network of 50 CubeSats, each performing identical ... [more ▼]

The QB50 mission has the scientific objective to study the temporal and spatial variations of a number of key parameters in the lower thermosphere with a network of 50 CubeSats, each performing identical in-situ measurements. One of these 50 CubeSats, the von Karman Institute Atmospheric Re-Entry CubeSat, will further be equipped by a thermal protection system and a dedicated sensor pack to study the atmospheric re-entry. This paper is devoted to the orbital dynamics analysis performed for the QB50 mission and the atmospheric re-entry trajectory analysis for a double unit CubeSat. The main focus is on the sensitivity of the results on atmospheric models, drag coefficient and the launch date. Typical atmospheric re-entry trajectories, including the stagnation point heat flux values are calculated using three different methods for three different scenarios. The predicted heat flux values will be used in the preliminary design of the thermal protection system of the VKI atmospheric re-entry CubeSat, which is to be the first CubeSat to be used as an atmospheric re-entry demonstrator. [less ▲]

Detailed reference viewed: 82 (1 ULg)
See detailDetection and quantification of non-linear dynamic behaviour of space structures
Hot, A.; Kerschen, Gaëtan ULg; Cogan, S. et al

in 28th International Modal Analysis Conference, Jacksonville, 2010 (2010)

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See detailDesign procedure of a nonlinear vibration absrober: enhancement of the amplitude robustness
Viguié, R.; Kerschen, Gaëtan ULg

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

Nonlinear vibration absorbers are known as being frequency-robust but not amplitude-robust devices. This lack of amplitude robustness is due to the frequency-energy dependence of their related nonlinear ... [more ▼]

Nonlinear vibration absorbers are known as being frequency-robust but not amplitude-robust devices. This lack of amplitude robustness is due to the frequency-energy dependence of their related nonlinear oscillations. This feature makes the design of nonlinear vibration absorbers a particulary challenging problem. In this paper an innovative design procedure of a nonlinear vibration absorber is proposed so that a nonlinear mode of a nonlinear primary structure can be controlled in a frequency and amplitude robustness fashion. [less ▲]

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See detailOn the functional form of a nonlinear vibration absorber
Viguié, V; Kerschen, Gaëtan ULg

in Journal of Sound & Vibration (2010), 329

Due to the frequency–energy dependence of nonlinear oscillations, nonlinear dynamical absorbers present interesting properties for mitigating unwanted vibrations in mechanical systems. Unlike the tuned ... [more ▼]

Due to the frequency–energy dependence of nonlinear oscillations, nonlinear dynamical absorbers present interesting properties for mitigating unwanted vibrations in mechanical systems. Unlike the tuned mass damper, the functional form of a nonlinear absorber is not known a priori and must be determined. This short note addresses this issue when a light-weight nonlinear absorber is attached to a nonlinear primary structure. Numerical simulations demonstrate that the determination of an adequate functional form may be directly linked to the frequency–energy dependence of the primary structure. [less ▲]

Detailed reference viewed: 11 (0 ULg)
See detailAdvanced Strategies for Nonlinear System Identification
Kerschen, Gaëtan ULg

in Vakakis, A. F. (Ed.) Advanced Nonlinear Strategies for Vibration Mitigation and System Identification (2010)

Detailed reference viewed: 26 (4 ULg)