References of "Kerschen, Gaëtan"
     in
Bookmark and Share    
See detailThermal model reduction using the super-face concept
Masset, Luc ULg; Bruls, Olivier ULg; Kerschen, Gaëtan ULg

Conference (2011)

The objective of this presentation is to carry out thermal model reduction in the context of the finite element method. The finite element model is decomposed in several sets of adjacent faces called ... [more ▼]

The objective of this presentation is to carry out thermal model reduction in the context of the finite element method. The finite element model is decomposed in several sets of adjacent faces called super-faces. Specialized algorithms such as the METIS partitioning algorithm are used to automatically generate the super-faces. Several constraints may be imposed, e.g., the size of the super-face, its aspect ratio or its aperture angle. Once the model is decomposed, view factors between super-faces are calculated with direct numerical integration or ray-tracing methods. This method offers a very substantial reduction of the computational burden compared to the full model, which is particularly interesting for pre-design studies or specific applications such as deployable structures. [less ▲]

Detailed reference viewed: 30 (13 ULg)
Full Text
See detailAssessment of nonlinear system identification methods using the SmallSat spacecraft structure
Kerschen, Gaëtan ULg; Soula, L.; Vergniaud, J.B. et al

in Proceedings of the 29th International Modal Analysis Conference (2011)

In this paper, several techniques for nonlinear system identification are applied to a real-world structure, the SmallSat spacecraft structure developed by EADS-Astrium. This composite structure comprises ... [more ▼]

In this paper, several techniques for nonlinear system identification are applied to a real-world structure, the SmallSat spacecraft structure developed by EADS-Astrium. This composite structure comprises two vibration isolation systems, one of which possesses mechanical stops. The loading case considered in the present study is a random (local) excitation. A careful progression through the different steps of the system identification process, namely detection, characterization and parameter estimation, is carried out. Different methods are applied to data resulting from numerical experiments, without having access to the finite element model which generated these data. [less ▲]

Detailed reference viewed: 16 (0 ULg)
Full Text
See detailIdentification expérimentale et recalage d'une structure au comportement élastodynamique non-linéaire
Hot, A.; Kerschen, Gaëtan ULg; Cogan, S. et al

in Actes du 20ème Congrès Francais de Mécanique (2011)

This paper studies of the COST-F3 beam experimental benchmark that exhibits a geometric non-linear behavior. The whole identification process, i.e. the non-linear behaviour detection, characterisation and ... [more ▼]

This paper studies of the COST-F3 beam experimental benchmark that exhibits a geometric non-linear behavior. The whole identification process, i.e. the non-linear behaviour detection, characterisation and the parameter estimation, is carried out using measured time and frequency responses. A finite element model is also built in order to update the non-linear parameter using the hybrid multi-harmonic balance extended constitutive relation error method. [less ▲]

Detailed reference viewed: 17 (1 ULg)
Full Text
Peer Reviewed
See detailTuning methodology of nonlinear vibration absorbers coupled to nonlinear mechanical systems
Viguié, R.; Kerschen, Gaëtan ULg

in Proceedings of the ASME International Design Engineering Technical Conferences (2011)

A large body of literature exists regarding linear and nonlinear dynamic absorbers, but the vast majority of it deals with linear primary structures. However, nonlinearity is a frequent occurrence in ... [more ▼]

A large body of literature exists regarding linear and nonlinear dynamic absorbers, but the vast majority of it deals with linear primary structures. However, nonlinearity is a frequent occurrence in engineering applications. Therefore, the present paper focuses on the mitigation of vibrations of nonlinear primary systems using nonlinear dynamic absorbers. Because most existing contributions about their design rely on extensive parametric studies, which are computationally demanding, or on analytic methods, which may be limited to small-amplitude motions, this study proposes a tuning procedure which is computationally tractable and can treat strongly nonlinear regimes of motion. The proposed methodology relies on a frequency-energy based approach followed by bifurcation analysis. The results are illustrated using a one-degree-of-freedom primary system, which can, for instance, represent the vibrations of a specific mode of a multi-degree-of-freedom structure. [less ▲]

Detailed reference viewed: 14 (0 ULg)
Full Text
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 ▲]

Detailed reference viewed: 14 (0 ULg)
Full Text
Peer Reviewed
See detailProper Orthogonal Decomposition for Nonlinear Radiative Heat Transfer Problems
Hickey, D.; Masset, Luc ULg; Kerschen, Gaëtan ULg et al

in Proceedings of the ASME International Design Engineering Technical Conferences (2011)

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 is then extended by adding nonlinear radiative heat exchanges between the beam and an enclosing box. The radiative view factors, present in the equations governing the heat fluxes between beam and box elements, are obtained with a raytracing method. A reduction procedure is proposed for this fully coupled nonlinear, multiphysical, thermomechanical system. Two alternative approaches to the reduction are investigated, a monolithic approach incorporating a scaling factor to the equations, and a partitioned approach that treats the individual physical modes separately. The paper builds on previous work presented previously by the authors. The results are given for the RMS error between either approach and the original, full solution. [less ▲]

Detailed reference viewed: 19 (7 ULg)
See detailDesign of the on-board computer of OUFTI-1 CubeSat
De Dijcker, S.; Crosset, N.; Verly, Jacques ULg et al

Conference (2011)

Detailed reference viewed: 19 (1 ULg)
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)
Full Text
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 ▲]

Detailed reference viewed: 35 (6 ULg)
Full Text
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)

Detailed reference viewed: 43 (7 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 9 (0 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 37 (5 ULg)
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: 36 (5 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 ▲]

Detailed reference viewed: 23 (6 ULg)
Full Text
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 ▲]

Detailed reference viewed: 92 (21 ULg)
Full Text
See detailToward robust parameterized reduced-order models of non-linear structures using POD
Hoffait, Sébastien ULg; Kerschen, Gaëtan ULg; Bruls, Olivier ULg

in IV European Conference on Computational Mechanics, Paris, 2010 (2010)

Detailed reference viewed: 37 (11 ULg)
See detailFinite element analysis of strongly nonlinear phenomena in deployable flexible systems
Bruls, Olivier ULg; Hoffait, Sébastien ULg; Cugnon, Frederic et al

in 1st ESA Multibody Dynamics Workshop on Multibody Dynamics for Space Applications, Noordwijk, 2010 (2010)

Detailed reference viewed: 28 (4 ULg)
Full Text
Peer Reviewed
See detailDynamic analysis of the self-locking phenomenon in tape spring hinges
Hoffait, Sébastien ULg; Bruls, Olivier ULg; Granville, Didier et al

in Acta Astronautica (2010), 66(7-8), 1125-1132

This paper investigates the dynamic behaviour of tape-spring hinges that are commonly used in space deployable structures. During the deployment of an appendice (e.g. a solar panel or a beam), a tape ... [more ▼]

This paper investigates the dynamic behaviour of tape-spring hinges that are commonly used in space deployable structures. During the deployment of an appendice (e.g. a solar panel or a beam), a tape-spring hinge allows the simultaneous achievement of the actuating, guiding and self-locking functions without friction elements. The proposed finite element model is able to capture buckling and hysteresis phenomena, which have a strong influence on the 3D motion of the system. A detailed analysis of those effects is developed, leading to a physical explanation of the crucial self-locking phenomenon. [less ▲]

Detailed reference viewed: 93 (16 ULg)