References of "Kerschen, Gaëtan"
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See detailEfficiency of TET in coupled oscillators associated with 1: resonance: Part 1
Quinn, D. Dane; Gendelman, Oleg; Kerschen, Gaëtan ULg et al

in Journal of Sound & Vibration (2008), 311

We study targeted energy transfers and nonlinear transitions in the damped dynamics of a two degree-of-freedom system of coupled oscillators (a linear oscillator with a lightweight, essentially nonlinear ... [more ▼]

We study targeted energy transfers and nonlinear transitions in the damped dynamics of a two degree-of-freedom system of coupled oscillators (a linear oscillator with a lightweight, essentially nonlinear, ungrounded attachment), caused by 1:1 resonance captures of the dynamics. Part I of this work deals with the underlying structure of the Hamiltonian dynamics of the system, and demonstrates that, for sufficiently small values of viscous damping, the damped transitions are strongly influenced by the underlying topological structure of periodic and quasiperiodic orbits of the corresponding Hamiltonian system. Focusing exclusively on 1:1 resonance captures in the system, it is shown that the topology of these damped transitions affect drastically the efficiency of passive energy transfer from the linear system to the nonlinear attachment. Then, a detailed computational study of the different types of nonlinear transitions that occur in the weakly damped system is presented, together with an analytical treatment of the nonlinear stability of certain families of periodic solutions of the underlying Hamiltonian system that strongly influence the said transitions. As a result of these studies, conditions on the system and forcing parameters that lead to effective or even optimal energy transfer from the linear system to the nonlinear attachment are determined. In Part II of this work, direct analytical treatment of the governing strongly nonlinear damped equations of motion is performed, in order to analytically model the dynamics in the region of optimal energy transfer, and to determine the characteristic time scales of the dynamics that influence the capacity of the nonlinear attachment to passively absorb and locally dissipate broadband energy from the linear oscillator. r 2007 Elsevier Ltd. All rights reserved [less ▲]

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See detailNonlinear Normal Modes, Part I: An Attempt To Demystify Them
Kerschen, Gaëtan ULg; Peeters, Maxime ULg; Golinval, Jean-Claude ULg 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 companions, Parts II and III. Because there is virtually no application of the NNMs to large-scale engineering ... [more ▼]

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companions, Parts II and III. Because there is virtually no application of the NNMs to large-scale engineering structures, these papers are an attempt to highlight several aspects that might drive their development in the future. Specifically, we support that (i) numerical methods for the continuation of periodic solutions pave the way for an effective and practical computation of NNMs, and (ii) time-frequency analysis is particularly suitable for the analysis of the resulting dynamics. Another objective of the present paper is to describe, in simple terms, and to illustrate the fundamental properties of NNMs. This is achieved to convince the structural dynamicist not necessarily acquainted with them that they are a useful framework for the analysis of nonlinear vibrating structures. [less ▲]

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See detailEfficient targeted energy transfers in coupled nonlinear oscillators through 1:1 transcient resonance captures:
Sapsis, Themistoklis; Quinn, D. Dane; Gendelman, Oleg et al

in Sixth EUROMECH Nonlinear Dynamics Conference, Saint Petersbourg, 2008 (2008)

We study targeted energy transfer (TET) in a two degree-of-freedom damped system caused by 1:1 transient resonance capture (TRC). The system consists of a linear oscillator strongly coupled to an ... [more ▼]

We study targeted energy transfer (TET) in a two degree-of-freedom damped system caused by 1:1 transient resonance capture (TRC). The system consists of a linear oscillator strongly coupled to an essentially nonlinear attachment. First, we study the underlying structure of the Hamiltonian dynamics of the system, and then show that, for sufficiently small values of viscous damping, the nonlinear damped transitions are strongly influenced by the underlying topological structure of periodic and quasiperiodic orbits of the hamiltonian system. Then, a detailed computational study of the different types of nonlinear transitions that occur in the weakly damped system is presented. As a result of these studies, conditions that lead to effective or even optimal TET from the linear system to the nonlinear attachment are determined. Finally, direct analytical treatment of the governing strongly nonlinear damped equations of motion is performed through slow/fast partition of the transient responses, in order to analytically model the dynamics the region of optimal TET, and to determine the characteristic time scales of the dynamics that influence the capacity of the nonlinear attachment to passively absorb and locally dissipate broadband energy from the linear oscillator. [less ▲]

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See detailTheoretical Understanding of Targeted Energy Transfers for Suppressing Aeroelastic Instabilities in a Nonlinear Aeroelastic Test Apparatus
Lee, Young S.; McFarland, D. Michael; Kerschen, Gaëtan ULg et al

in 45th Technical Meeting of the Society of Engineering Science, Urbana Champaign, 2008 (2008)

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See detailEnhancing robustness of aerolastic instability suppression using MDOF energy sinks
Lee, Young S.; Vakakis, Alexander F.; Bergman, Lawrence A. et al

in AIAA Journal (2008), 46(6), 1371-1394

In this last of a three paper sequence, we use simultaneous multimodal broadband targeted energy transfers to multi-degree-of-freedom nonlinear energy sinks to improve the robustness of aeroelastic ... [more ▼]

In this last of a three paper sequence, we use simultaneous multimodal broadband targeted energy transfers to multi-degree-of-freedom nonlinear energy sinks to improve the robustness of aeroelastic instability suppression of a rigid wing with structural nonlinearities. A numerical bifurcation analysis of limit cycle oscillations of the wing with the multi-degree-of-freedom nonlinear energy sinks attached shows that controlling the lower parameter value for limit point cycle bifurcation to occur above Hopf bifurcation is crucial to enhancing the robustness of limit cycle oscillation suppression. We demonstrate that multi-degree-of-freedom nonlinear energy sinks can greatly enhance the robustness of limit cycle oscillation suppression, compared with single-degree-of-freedom nonlinear energy sinks (which were studied in our previous papers), with a much smaller total mass.We also investigate the nonlinear modal interactions that occur between the aeroelastic modes and the multi-degree-of-freedom nonlinear energy sinks, in an effort to gain a physical understanding of the mechanisms governing instability suppression. We demonstrate that a properly designed multi-degree-of-freedom nonlinear energy sink provides robustness of aeroelastic instability suppression by efficiently, passively, and rapidly transferring a significant portion of unwanted vibration energy to the furthest mass of the nonlinear energy sink. Consideration of other types of multi-degree-of-freedom nonlinear energy sinks suggests that the robustness enhancement is achieved by the concentrated mass effect of the attached nonlinear energy sinks. [less ▲]

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See detailIdentification of the Slow-Flow Dynamics of Transonic Aeroelastic Response from Time-Series Data
Lee, Y. S.; Vakakis, Alexander F.; McFarland, D. M. et al

in 45th Technical Meeting of the Society of Engineering Science, Urbana Champaign, 2008 (2008)

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See detailComputation of nonlinear normal modes, part II: numerical continuation in Auto
Serandour, Guillaume; Peeters, Maxime ULg; Kerschen, Gaëtan ULg et al

in Sixth EUROMECH Nonlinear Dynamics Conference, Saint Petersbourg, 2008 (2008)

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companion, Part I. Because there is virtually no application of the NNMs to large-scale engineering structures, these ... [more ▼]

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companion, Part I. Because there is virtually no application of the NNMs to large-scale engineering structures, these papers are an attempt to highlight one aspect that might drive their development in the future. Specifically, we support that numerical methods for the continuation of periodic solutions pave the way for an effective and practical computation of NNMs. In this context, we show that the NNMs computation is possible using an existing continuation software, namely AUTO07. This is demonstrated using a 2DOF nonlinear system. The results are compared with those obtained with the Matlab algorithm described in Part I. [less ▲]

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See detailCOMPUTATION OF NONLINEAR NORMAL MODES, PART I: NUMERICAL CONTINUATION IN MATLAB
Peeters, Maxime ULg; Viguié, Régis ULg; Serandour, Guillaume et al

in Sixth EUROMECH Nonlinear Dynamics Conference, Saint Petersbourg, 2008 (2008)

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companion, Part II. Because there is virtually no application of the NNMs to large-scale engineering structures ... [more ▼]

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companion, Part II. Because there is virtually no application of the NNMs to large-scale engineering structures, these papers are an attempt to highlight one aspect that might drive their development in the future. Specifically, we support that numerical methods for the continuation of periodic solutions pave the way for an effective and practical computation of NNMs. In this context, we show that the NNM computation is possible with limited implementation effort. The proposed algorithm, implemented in MATLAB, relies on two main techniques, namely a shooting procedure and a method for the continuation of NNM motions. The algorithm is demonstrated using a 2DOF nonlinear system. A comparison with the results given by the AUTO software is achieved in Part II. [less ▲]

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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 detailEmpirical Mode Decomposition in the Reduced-Order Modeling of Aeroelastic Systems
Lee, Young S; McFarland, D. Michael; Vakakis, Alexander F. et al

in 49th AIAA Structural Dynamics and Materials Conference, Shaumberg, 2008 (2008)

A relationship between IntrinsicMode Functions (IMFs), derived from the Empirical Mode Decomposition (EMD), and the slow-flow model of a nonlinear dynamical system has been exploited in the development of ... [more ▼]

A relationship between IntrinsicMode Functions (IMFs), derived from the Empirical Mode Decomposition (EMD), and the slow-flow model of a nonlinear dynamical system has been exploited in the development of the Slow Flow Model Identification (SFMI) method for strongly nonlinear systems, in which the physical parameters of such systems are identified from experimental data. Both the slow flows and IMFs provide the means to expand a general multicomponent signal in terms of a series of simpler, dominant, monocomponent signals. The slow flows are obtained analytically, for example through application of the method of complexification and averaging (CxA), which transforms the equations of motion into a set of approximate equations in amplitude and phase for each modeled frequency component. In contrast, the EMD characterizes a signal through the envelope and phase of its elemental components, the IMFs. Thus, between nonlinear transitions, the equations derived using the CxA method govern the amplitude and phase of the modeled IMFs. Application of SFMI has, until now, been limited to low-dimensional systems subjected to impulsive excitation. Herein, the method is extended to identification of a planar rigid airfoil [less ▲]

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See detailTargeted Energy Transfers for Suppressing Aeroelastic Instability due to Unsteady Lift
Vakakis, Alexander F.; Bergman, Lawrence A.; McFarland, D. M. et al

in AVT-152 Symposium on Limit Cycle Oscillations, Norway, 2008 (2008)

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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 detailEfficiency of Targeted Energy Transfers in Coupled Nonlinear Oscillators Associated with 1:1 Resonance Captures
Sapsis, T.; Vakakis, Alexander F.; Gendelman, O. V. et al

in 45th Technical Meeting of the Society of Engineering Science, Urbana Champaign, 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 detailToward an Optimal Design Procedure of a Nonlinear Vibration Absorber Coupled to a Duffing Oscillator
Viguié, Régis ULg; Kerschen, Gaëtan ULg

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

In the present study, the focus is set on the development of a design methodology for nonlinear vibration absorbers, termed nonlinear energy sink (NES), to optimize the vibrating level reduction on a ... [more ▼]

In the present study, the focus is set on the development of a design methodology for nonlinear vibration absorbers, termed nonlinear energy sink (NES), to optimize the vibrating level reduction on a Duffing oscillator. The idea lies in the assessment of a duality property between, on the one hand, the tuning procedure of the tuned mass damper (TMD) coupled to a linear oscillator and, on the other hand, the assumed design scheme of NES coupled to a purely nonlinear Duffing oscillator. To this end, the basics on the TMD tuning methodology are recalled and extended to the concept of frequency-energy plot (FEP) [1]. Then, based upon this concept, the development of a NES design procedure is undertaken and the related dynamics analyzed. Finally, it is shown how to design a vibration absorber to deal with a general Duffing oscillator. [less ▲]

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See detailOUFTI-1: The CubeSat developed at the University of Liège, Belgium
Galli, S.; Pisane, Jonathan ULg; Ledent, P. et al

Conference (2008)

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See detailExploration of nonlinear shunting strategies as effective vibration absorbers
Viguié, Régis ULg; Peeters, Maxime ULg; Kerschen, Gaëtan ULg et al

in 45th Technical Meeting of the Society of Engineering Science, Urbana Champaign, 2008 (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 detailTargeted energy transfers in vibro-impact oscillators for seismic mitigation
Nucera, F.; Vakakis, Alexander F.; McFarland, D. M. et al

in Nonlinear Dynamics (2007), 50(3), 651-677

In the field of seismic protection of structures, it is crucial to be able to diminish 'as much as possible' and dissipate 'as fast as possible' the load induced by seismic (vibration-shock) energy ... [more ▼]

In the field of seismic protection of structures, it is crucial to be able to diminish 'as much as possible' and dissipate 'as fast as possible' the load induced by seismic (vibration-shock) energy imparted to a structure by an earthquake. In this context, the concept of passive nonlinear energy pumping appears to be natural for application to seismic mitigation. Hence, the overall problem discussed in this paper can be formulated as follows: Design a set of nonlinear energy sinks (NESs) that are locally attached to a main structure, with the purpose of passively absorbing a significant part of the applied seismic energy, locally confining it and then dissipating it in the smallest possible time. Alternatively, the overall goal will be to demonstrate that it is feasible to passively divert the applied seismic energy from the main structure (to be protected) to a set of preferential nonlinear substructures (the set of NESs), where this energy is locally dissipated at a time scale fast enough to be of practical use for seismic mitigation. It is the aim of this work to show that the concept of nonlinear energy pumping is feasible for seismic mitigation. We consider a two degree-of-freedom (DOF) primary linear system (the structure to be protected) and study seismic-induced vibration control through the use of Vibro-Impact NESs (VI NESs). Also, we account for the possibility of attaching to the primary structure additional alternative NES configurations possessing essential but smooth nonlinearities (e.g., with no discontinuities). We study the performance of the NESs through a set of evaluation criteria. The damped nonlinear transitions that occur during the operation of the VI NESs are then studied by superimposing wavelet spectra of the nonlinear responses to appropriately defined frequency - energy plots (FEPs) of branches of periodic orbits of underlying Conservative systems. [less ▲]

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