References of "Kerschen, Gaëtan"
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See detailPropellantless rendez-vous of QB50 nanosatellites
Dell'Elce, Lamberto ULg; Kerschen, Gaëtan ULg

in Proceedings of the 63rd IAC (2012)

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See detailTowards a “concurrent design facility (CDF)” for nanosatellites: a back-of-the-envelope calculation of the overall energy budget of OUFTI-1
Denis, Amandine ULg; Crosset, Nicolas ULg; Pisane, Jonathan ULg et al

Conference (2012)

We give a very compact account of the overall energy budget of the OUFTI-1 nanosatellite, thereby providing a useful guide for future designs, as well as an explanation of why a nanosatellite can ... [more ▼]

We give a very compact account of the overall energy budget of the OUFTI-1 nanosatellite, thereby providing a useful guide for future designs, as well as an explanation of why a nanosatellite can, energetically, survive and do useful tasks in space. [less ▲]

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See detailOrbital rendez-vous using differential drag in the QB50 constellation
Dell'Elce, Lamberto ULg; Kerschen, Gaëtan ULg

in Proceedings of the AIAA/AAS Astrodynamics Specialist Conference (2012)

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See detailDesign of an uncertain prestressed space structure: an info-gap approach
Hot, A.; Cogan, S.; Foltete, E. et al

in Proceedings of the 30th International Modal Analysis Conference (2012)

Uncertainty quantification is an integral part of the model validation process and is important to take into account during the design of mechanical systems. Sources of uncertainty are diverse but ... [more ▼]

Uncertainty quantification is an integral part of the model validation process and is important to take into account during the design of mechanical systems. Sources of uncertainty are diverse but generally fall into two categories: aleatory uncertainties due to random processes and epistemic uncertainty resulting from a lack of knowledge or erroneous assumptions. This work focuses on the impact of uncertain levels of prestress on the behavior of solar arrays in their stowed configuration. In this context, snubbers are inserted between two adjacent panels to maintain contact and absorb vibrations during launch. However, under high excitation loads, a loss of contact between the two panels may occur. This results in impacts that can cause extensive damages to fragile elements. In practice, the specific load configuration for which the separation of the two panels occurs is difficult to determine precisely since the exact level of prestress applied to the structure is unknown. An info-gap robustness analysis is applied to study the impact of this lack of knowledge on the prestress safety factor required to avoid loss of contact. The proposed methodology is illustrated using a simplified model of a solar array. [less ▲]

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See detailThe nonlinear tuned vibration absorber
Viguié, R.; Kerschen, Gaëtan ULg

in Proceedings of the International Conference on Structural Nonlinear Dynamics and Diagnosis (2012)

The objective of this paper is to introduce a new nonlinear dynamical absorber, the nonlinear tuned vibration absorber, through a rigorous nonlinear extension of the tuning rule for the linear tuned ... [more ▼]

The objective of this paper is to introduce a new nonlinear dynamical absorber, the nonlinear tuned vibration absorber, through a rigorous nonlinear extension of the tuning rule for the linear tuned vibration absorber. This nonlinear tuning methodology combined with the increased suppression bandwidth brought by the intentional use of nonlinearity leads to the development of an absorber that is effective in wide ranges of frequencies and motion amplitudes. The results are illustrated using a one-degree-of-freedom primary system. [less ▲]

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See detailNonlinear Structural Dynamics: Theory, Simulation and Testing, KEYNOTE LECTURE
Kerschen, Gaëtan ULg

in Proceedings of the 18th Symposium on Vibrations, Shocks and Noise (2012)

Nonlinearity is a frequent occurrence in engineering structures. It is at the origin of rich and complex dynamical phenomena that cannot be observed in linear structures. The analysis of the dynamics of ... [more ▼]

Nonlinearity is a frequent occurrence in engineering structures. It is at the origin of rich and complex dynamical phenomena that cannot be observed in linear structures. The analysis of the dynamics of nonlinear systems therefore warrants the development of rigorous and effective methods and is the focus of this presentation. Several theoretical, computational and experimental methods will be presented and applied to a real-life, full-scale nonlinear structure, the EADS- Astrium SmallSat spacecraft. [less ▲]

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See detailNon-linear structures
Newerla, A.; Kerschen, Gaëtan ULg

in Calvi, A.; Roy, N. (Eds.) Spacecraft Loads Analysis (2012)

Non-linearity is a frequent occurrence in engineering structures including spacecraft structures. It can take different forms, and it is at the origin of various dynamical phenomena with no linear ... [more ▼]

Non-linearity is a frequent occurrence in engineering structures including spacecraft structures. It can take different forms, and it is at the origin of various dynamical phenomena with no linear counterpart. These phenomena include jumps, harmonics, bifurcation and non-unicity of the solutions. Even when they are local, non-linearities can affect the global dynamical behaviour of a structure and have a substantial impact on spacecraft loads. What makes non-linear dynamics challenging to analyse and model is the well-known result that the principle of linear superposition does not (generally) apply to non-linear systems. Even if linearisation may suffice in some cases, the rigorous analysis of non-linear structures requires adequate and dedicated numerical and experimental methodologies. The main objective of this chapter is to describe how to handle non-linearities for an accurate estimation of loads in spacecraft structures. Specifically, guidelines for both modeling and testing are provided. [less ▲]

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See detailTopics in Nonlinear Dynamics
Adams, D.A.; Kerschen, Gaëtan ULg; Carrella, A.

Book published by Springer (2012)

Topics in Nonlinear Dynamics, Volume 3, Proceedings of the 30th IMAC, A Conference and Exposition on Structural Dynamics, 2012, the third volume of six from the Conference, brings together 26 ... [more ▼]

Topics in Nonlinear Dynamics, Volume 3, Proceedings of the 30th IMAC, A Conference and Exposition on Structural Dynamics, 2012, the third volume of six from the Conference, brings together 26 contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Structural Dynamics. [less ▲]

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See detailThe Sun-earth Imbalance radiometer for a direct measurement of the net heating of the Earth
Dewitte, S; Chevalier, A; Meftah, M et al

Conference (2012)

Although it is generally accepted that the climate on earth is changing due to a radiative energy imbalance at the top of the atmosphere, up to now this radiation imbalance has not been measured directly ... [more ▼]

Although it is generally accepted that the climate on earth is changing due to a radiative energy imbalance at the top of the atmosphere, up to now this radiation imbalance has not been measured directly. The measurement is challenging both in terms of space-time sampling of the radiative energy that is leaving the earth and in terms of accuracy. The incoming solar radiation and the outgoing terrestrial radiation are of nearly equal magnitude – of the order of 340 W/m² – resulting in a much smaller difference or imbalance of the order of 1 W/m². The only way to measure the imbalance with sufficient accuracy is to measure both the incoming solar and the outgoing terrestrial radiation with the same instrument. By reanalyzing data from the NASA LARC Earth Radiation Budget Experiment, we have been able to demonstrate that the sampling problem can be overcome, even with the low resolution Wide Field of View radiometer. We have combined the measurements of the precessing ERBS satellite for midlatitude and equatorial regions with measurements of the sun synchronuous NOAA9 satellite for the polar regions. For the accuracy requirement an improved instrument design is needed. We propose a new instrument, which we call the Sun-earth IMBAlance (SIMBA) radiometer. It is an improved wide field of view cavity radiometer based on our long experience with the DIARAD type of instrument for the measurement of Total Solar Irradiance. Currently we have two DIARAD instruments in space, on SOHO and on the ISS, and a third one will be launched this year on the Picard microsatellite. In this paper, we will present the ERBE sampling study and the SIMBA instrument and nanosatellite design [less ▲]

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See detailNonlinear modal analysis of the SmallSat spacecraft
Renson, Ludovic ULg; Kerschen, Gaëtan ULg; Newerla, Alfred

in Proceedings of the SEM IMAC XXX Conference (2012)

Non-linear elements are present in practically all spacecraft structures. The assumption of a (quasi-)linear structure is nevertheless adequate for structural analyses and design verification purposes in ... [more ▼]

Non-linear elements are present in practically all spacecraft structures. The assumption of a (quasi-)linear structure is nevertheless adequate for structural analyses and design verification purposes in those cases where these structural non-linearities are relatively weak or not substantially activated by the mechanical environments encountered during the launch or during ground testing. However, when significant non-linear effects in spacecraft structures are no longer negligible then linear modal analysis will not be able to handle non-linear dynamical phenomena in an adequate manner: the development of a non-linear analogue of linear modal analysis becomes an urgent and important issue. The objective of this paper is to show that nonlinear normal modes (NNMs) represent a useful and practical tool in this context. A full-scale spacecraft structure is considered and is modeled using the finite element method. Its NNMs are computed using advanced numerical algorithms, and the resulting dynamics is then carefully analyzed. Nonlinear phenomena with no linear counterpart including nonlinear modal interactions are also highlighted. [less ▲]

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See detailContract 21539/08/NL/SFe - Advancement of mechanical verification methods for non-linear spacecraft: Exploitation of test data
Noël, Jean-Philippe ULg; Kerschen, Gaëtan ULg

Report (2011)

The objective of this technical note is to apply the nonlinear system identification techniques described in the technical note "Nonlinearity identification methods: predictive analyses" to the ... [more ▼]

The objective of this technical note is to apply the nonlinear system identification techniques described in the technical note "Nonlinearity identification methods: predictive analyses" to the experimental data gathered on the SmallSat spacecraft structure. Guidelines for nonlinear spacecraft testing and identification are also be provided. [less ▲]

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See detailNonlinear modal analysis of aerospace structures
Peeters, Maxime ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg et al

in Proceedings of the 3rd International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (2011)

The dynamic systems theory is well-established for linear systems and can rely on mature tools such as the theories of linear operators and linear integral transforms. This is why theoretical and ... [more ▼]

The dynamic systems theory is well-established for linear systems and can rely on mature tools such as the theories of linear operators and linear integral transforms. This is why theoretical and experimental modal analysis, i.e., the computation of vibration modes from a mathematical model and from experimental data, respectively, is really quite sophisticated and advanced. Even though linear modal analysis served, and is still serving, the structural dynamics community for applications ranging from bridges to satellites, it is commonly accepted that nonlinearity is a frequent occurrence in engineering structures. Because linear modal analysis fails in the presence of nonlinear dynamical phenomena, the development of a practical nonlinear analog of modal analysis would be an extremely timely contribution; it is clearly missing in the structural dynamics literature. A new framework for nonlinear modal analysis of real-world structures, which includes the computation of nonlinear modes from finite element models, is introduced in this paper. This framework will permit a rigorous, yet understandable by the practicing engineer, analysis of nonlinear dynamical phenomena. It will also provide solid theoretical foundations for extending finite element model validation to nonlinear aerospace structures. [less ▲]

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See detailNonlinear normal modes of real-world structures: application to a full-scale aircraft
Peeters, Maxime ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg et al

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

The objective of this paper is to demonstrate that the numerical computation of the nonlinear normal modes (NNMs) of complex real-world structures is now within reach. The application considered in this ... [more ▼]

The objective of this paper is to demonstrate that the numerical computation of the nonlinear normal modes (NNMs) of complex real-world structures is now within reach. The application considered in this study is the airframe of the Morane-Saulnier Paris aircraft, whose ground vibration tests have exhibited some nonlinear structural behaviors. The finite element model of this aircraft, elaborated from drawings, has more than 80000 degrees of freedom, and softening nonlinearities exist in the connection between the external fuel tanks and the wing tips. From this model, a reduced-order model, which is accurate in the [0-100Hz] range, is constructed using the Craig- Bampton technique. The NNMs of the reduced model are then computed using a numerical algorithm combining shooting and pseudo-arclength continuation. The results show that the NNMs of this full-scale structure can be computed accurately even in strongly nonlinear regimes and with a reasonable computational burden. Nonlinear modal interactions are also highlighted by the algorithm and are discussed. [less ▲]

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See detailNonlinear normal modes and band zones in granular chains with no precompression
Jayaprakash, K.R.; Starosvetsky, Y.; Vakakis, A.F. et al

in Nonlinear Dynamics (2011), 63

We study standing waves (nonlinear normal modes—NNMs) and band zones in finite granular chains composed of spherical granular beads in Hertzian contact, with fixed boundary conditions. Although these are ... [more ▼]

We study standing waves (nonlinear normal modes—NNMs) and band zones in finite granular chains composed of spherical granular beads in Hertzian contact, with fixed boundary conditions. Although these are homogeneous dynamical systems in the notation of Rosenberg, we show that the discontinuous nature of the dynamics leads to interesting effects such as separation between beads, NNMs that appear as traveling waves (these are characterized as pseudo-waves), and localization phenomena. In the limit of infinite extent, we study band zones, i.e., pass and stop bands in the frequency–energy plane of these dynamical systems, and classify the essentially nonlinear responses that occur in these bands. Moreover, we show how the topologies of these bands significantly affect the forced dynamics of these granular media subject to narrowband excitations. This work provides a classification of the coherent (regular) intrinsic dynamics of one-dimensional homogeneous granular chains with no pre-compression, and provides a rigorous theoretical foundation for further systematic study of the dynamics of granular systems, e.g., the effects of disorders or clearances, discrete breathers, nonlinear localized modes, and high-frequency scattering by local disorders. Moreover, it contributes toward the design of granular media as shock protectors, and in the passive mitigation of transmission of unwanted disturbances. [less ▲]

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See detailComputation of nonlinear normal modes of large structures: application to a full-scale aircraft
Peeters, Maxime ULg; Renson, Ludovic ULg; Kerschen, Gaëtan ULg et al

in Proceedings of the 7th European Nonlinear Dynamics Conference (ENOC 2011) (2011)

The objective of this paper is to demonstrate that the numerical computation of the nonlinear normal modes (NNMs) of complex real-world structures is now within reach. The application considered in this ... [more ▼]

The objective of this paper is to demonstrate that the numerical computation of the nonlinear normal modes (NNMs) of complex real-world structures is now within reach. The application considered in this study is the airframe of the Morane-Saulnier Paris aircraft, whose ground vibration tests exhibited some nonlinear structural behaviors. The NNMs are computed using a numerical algorithm combining shooting and pseudo-arclength continuation. [less ▲]

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See detailNonlinear Normal Modes: A Finite Element Approach
Renson, Ludovic ULg; Kerschen, Gaëtan ULg

Conference (2011)

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See detailPhase resonance testing of nonlinear vibrating structures
Peeters, Maxime ULg; Kerschen, Gaëtan ULg; Golinval, Jean-Claude ULg

in 28th International Modal Analysis Conference, Jacksonville, 2010 (2011)

Detailed reference viewed: 33 (13 ULg)
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 ▲]

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