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See detailDamage Diagnosis of Beam-like Structures Based on Sensitivities of Principal Component Analysis Results
Nguyen, Viet Ha ULg; Golinval, Jean-Claude ULg

in IMAC-XXVIII A Conference on Structural Dynamics (2010)

This paper addresses the problem of damage detection and localization in linear-form structures. Principal Component Analysis (PCA) is a popular technique for dynamic system investigation. The aim of the ... [more ▼]

This paper addresses the problem of damage detection and localization in linear-form structures. Principal Component Analysis (PCA) is a popular technique for dynamic system investigation. The aim of the paper is to present a damage diagnosis method based on sensitivities of PCA results in the frequency domain. Starting from Frequency Response Functions (FRFs) measured at different locations on the beam, PCA is performed to determine the main features of the signals. Sensitivities of principal directions obtained from PCA to beam parameters are then computed and inspected according to the location of sensors; their variation from the healthy state to the damaged state indicates damage locations. It is worth noting that damage localization is performed without the need of modal identification. Once the damage has been localized, its evaluation may be quantified if a structural model is available. This evaluation is based on a model updating procedure using previously estimated sensitivities. The efficiency and limitations of the proposed method are illustrated using numerical and experimental examples. [less ▲]

Detailed reference viewed: 70 (26 ULg)
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See detailDamage Localisation Using Principal Component Analysis of Distributed Sensor Array
De Boe, Pascal; Golinval, Jean-Claude ULg

Conference given outside the academic context (2001)

The spatial information given by the distributed sensors (e.g., piezoelectric laminates) can be used to forecast structural damage on localised critical spot. It is well known that a localised structural ... [more ▼]

The spatial information given by the distributed sensors (e.g., piezoelectric laminates) can be used to forecast structural damage on localised critical spot. It is well known that a localised structural damage with relative small amplitude does not affect significantly the modal response of the structure, at least at low frequencies. Nevertheless, a local de-lamination or electrode deterioration at the distributed sensor level will show significant changes on the response of the sensor by modifying its apparent electromechanical coupling. Assuming that the number of sensors is greater than the number of involved structural modes, a local structural damage, with relative small amplitude, will only affect a particular distributed sensor without affecting significantly the response of the others. By applying a principal component analysis (PCA) on the sensor time responses, it is possible to see that any change of one particular sensor electromechanical coupling factor will affect the subspace generated by the complete sensor response set. The subspace generated with the damaged structure can then be compared with the subspace of an initial state in order to diagnose damage or not. [less ▲]

Detailed reference viewed: 33 (0 ULg)
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See detailDamage localization in Linear-Form Structures Based on Sensitivity Investigation for Principal Component Analysis
Nguyen, Viet Ha ULg; Golinval, Jean-Claude ULg

in Journal of Sound & Vibration (2010), 329

This paper addresses the problem of damage detection and localization in linear-form structures. Principal Component Analysis (PCA) is a popular technique for dynamic system investigation. The aim of the ... [more ▼]

This paper addresses the problem of damage detection and localization in linear-form structures. Principal Component Analysis (PCA) is a popular technique for dynamic system investigation. The aim of the paper is to present a damage diagnosis method based on sensitivities of PCA results in the frequency domain. Starting from Frequency Response Functions (FRFs) measured at different locations on the structure; PCA is performed to determine the main features of the signals. Sensitivities of principal directions obtained from PCA to structural parameters are then computed and inspected according to the location of sensors; their variation from the healthy state to the damaged state indicates damage locations. It is worth noting that damage localization is performed without the need of modal identification. Influences of some features as noise, choice of parameter and number of sensors are discussed. The efficiency and limitations of the proposed method are illustrated using numerical and real-world examples. [less ▲]

Detailed reference viewed: 38 (10 ULg)
Peer Reviewed
See detailA damage model for elastoviscoplastic materials at large strains
Habraken, Anne ULg; Zhu, Y. Y.; Charlier, Robert ULg et al

in Proc. of the Int. Conf. on Computational Plasticity, Fundamentals and Applications, COMPLAS (1995, April)

Detailed reference viewed: 13 (2 ULg)
See detailDamage Model Identification Using Inverse Problem Methodology
KLEINERMANN, J. P.; Ponthot, Jean-Philippe ULg; Stainier, Laurent ULg

in proceedings of Plasticity’2000 (2000)

Detailed reference viewed: 18 (1 ULg)
Peer Reviewed
See detailDamage modeling of laminated composites
Nguyen, Ba Nghiep; Fleury, Claude ULg

in Owen, D. R. J.; Onate, E. (Eds.) Computational plasticity: fundamentals and applications: proceedings of the fourth international conference held in Barcelona, Spain, 3rd-6th, April, 1995. Part I (1997)

Detailed reference viewed: 5 (0 ULg)
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See detailDamage modelling in geotechnics: micromechanical approaches
Levasseur, Séverine ULg; Collin, Frédéric ULg; Charlier, Robert ULg et al

in Zhao, Jian; Labiouse, Vincent; Dudt, Jean-Paul (Eds.) et al EUROCK2010: Rock Mechanics in Civil and Environmental Engineering (2010)

The mechanical behaviours of geomaterials are significantly affected by the presence of voids or cracks-like defects. The modelling of such behaviour is classically performed by considering purely ... [more ▼]

The mechanical behaviours of geomaterials are significantly affected by the presence of voids or cracks-like defects. The modelling of such behaviour is classically performed by considering purely macroscopic or micromechanically-based damage models. In the perspective of applications in civil engineering or in geomechanics, we propose in this paper to evaluate a homogenization approach, based on Mori-Tanaka scheme, applied to microcracked materials. In order to provide an appropriate interpretation of the nonlinear behaviour at macro-scale, the crack-induced damage is coupled to friction phenomena on closed cracks lips. The predictions of the coupled model are first analysed on laboratory tests performed on Callovo-Oxfordian Clay. Then, they are extended to a numerical analysis of excavation damaged zones around tunnels. [less ▲]

Detailed reference viewed: 51 (1 ULg)
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See detailDamage prediction in incremental forming
Guzmán Inostroza, Carlos Felipe ULg

Diverse speeche and writing (2013)

Detailed reference viewed: 7 (5 ULg)
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See detailA damage/repair model for alveolar bone remodeling
Mengoni, Marlène ULg; Ponthot, Jean-Philippe ULg

in Middleton; Evans; Holt (Eds.) et al 8th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering : CMBBE2008, Porto, Porugal (2008)

Detailed reference viewed: 63 (19 ULg)
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See detailDie Dämonie von Verlassenheit und Fremde in den Erzählungen Stefan Zweigs
Küpper, Achim ULg

Scientific conference (2006, October 20)

Detailed reference viewed: 13 (0 ULg)
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See detailDie Dämonie von Verlassenheit und Fremde in den Erzählungen Stefan Zweigs. Abstract
Küpper, Achim ULg

in Stefan Zweig und das Dämonische: Abstracts (2006)

Detailed reference viewed: 2 (0 ULg)
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See detailDamped LYalpha Absorbers and Gravitational Lensing
Smette, Alain; Claeskens, Jean-François ULg; Surdej, Jean ULg

in Structure and Evolution of the Intergalactic Medium from QSO Absorption Line System, Proceedings of the 13th IAP Astrophysics Colloquium (1997)

Not Available

Detailed reference viewed: 5 (3 ULg)
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See detailDamping control by fusion of reinforcement learning and control Lyapunov functions
Glavic, Mevludin; Wehenkel, Louis ULg; Ernst, Damien ULg

in Proceedings of the 38th North American Power Symposium (NAPS 2006) (2006)

The main idea behind the concept, proposed in the paper, is the opportunity to make control systems with increased capabilities by synergetic fusion of the domain-specific knowledge and the methodologies ... [more ▼]

The main idea behind the concept, proposed in the paper, is the opportunity to make control systems with increased capabilities by synergetic fusion of the domain-specific knowledge and the methodologies from control theory and artificial intelligence. The particular approach considered combines Control Lyapunov Functions (CLF), a constructive control technique, an Reinforcement Learning (RL) in attempt to optimize a mix of system stability and performance. Two control schemes are proposed and the capabilities of the resulting controllers are illustrated on a control problem involving a Thyristor Controlled Series Capacitor (TCSC) for damping oscillations in a four-machine power system. [less ▲]

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See detailDamping identification in a non-linear aeroelastic structure
Vio, Gareth A.; Prandina, Marco; Dimitriadis, Grigorios ULg

in Proceedings of ISMA2010 (2010, September 20)

An energy-based method is proposed to identify damping parameters from time histories of responses to sets of single-frequency harmonic excitation. The method is intended to be practically applicable to ... [more ▼]

An energy-based method is proposed to identify damping parameters from time histories of responses to sets of single-frequency harmonic excitation. The method is intended to be practically applicable to real structures and is able to identify the value of viscous damping, Coulomb friction and eventually other forms of non-linear damping models in aeroelastic systems. The inputs required are simply the accelerometer signals and the forces applied. It will be shown that if the system is undergoing Limit Cycle Oscillations, no external force is required for the identification process. [less ▲]

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See detailDamping identification of lightly damped linear dynamic systems using Common-base Proper Orthogonal Decomposition
Andrianne, Thomas ULg; Dimitriadis, Grigorios ULg

in Mechanical Systems & Signal Processing (2012), 28

This paper presents a new technique to identify the damping of linear systems. It is developed from the Proper Orthogonal Decomposition (POD) of the free response of the system and extended to the ... [more ▼]

This paper presents a new technique to identify the damping of linear systems. It is developed from the Proper Orthogonal Decomposition (POD) of the free response of the system and extended to the recently proposed Common-base POD (CPOD). The present application of CPOD considers simultaneously several free responses of the system to different initial conditions. The eigen-decomposition of the co-variance matrix leads to a unique vector basis which is likely to contain more information about the dynamics of the system than a vector basis obtained by the classic POD technique. The ability of the technique to estimate the mode shapes and the modal damping is demonstrated on a simulated mass-spring-damper system. Two different distributions of masses are considered in order to confront the CPOD analysis to the intrinsic limitation of POD, i.e. that the mode shapes are identified exactly only if the mass matrix is proportional to the identity matrix. It is shown that the identification of the damping is still possible when the modes are not orthonormal. The robustness of the technique is demonstrated in the presence of noise in the responses of the system and through an experimental application with comparison with other identifications techniques. [less ▲]

Detailed reference viewed: 76 (14 ULg)
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See detailDamping identification of linear dynamic systems using Common-base Proper Orthogonal Decomposition
Andrianne, Thomas ULg; Dimitriadis, Grigorios ULg

in Proceedings of ISMA2012 (2012, September 19)

This paper presents a novel identification technique of the modal damping of linear systems. It is based on the Proper Orthogonal Decomposition (POD) of the free response of the system and extended to the ... [more ▼]

This paper presents a novel identification technique of the modal damping of linear systems. It is based on the Proper Orthogonal Decomposition (POD) of the free response of the system and extended to the Common-base POD (CPOD) approach. Different initial conditions are applied to the system and the corresponding free responses are considered simultaneously. The CPOD technique leads to a unique vector basis which is likely to contain more information about the dynamics of the system than a vector basis obtained by the classic POD technique, based on one set of initial conditions only. The ability of the technique to estimate the modal damping is demonstrated on a simulated mass-spring-damper system and an experimental system. Good agreement is shown between the damping estimates of the CPOD technique and the ones of the LSCF technique. The advantage and limitations of the present technique are discussed. [less ▲]

Detailed reference viewed: 44 (3 ULg)
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See detailDamping material characterization and modeling: an industrial case-study
Poncelet, Fabien ULg; Bernay, Bruno; Kerschen, Gaëtan ULg et al

in International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE 2009), San Diego, 2009 (2009, August)

Turbojet engines contain potential nonlinearity sources such as geometric nonlinearities due to the slenderness and the length of modern blades, contacts between the blades and the shrouds, friction in ... [more ▼]

Turbojet engines contain potential nonlinearity sources such as geometric nonlinearities due to the slenderness and the length of modern blades, contacts between the blades and the shrouds, friction in the connections, and material nonlinearities. This paper focuses on the damping material which can be found in some stator stages of low-pressure compression parts. This material makes the shroud and all the blades of the stage interdependent, providing damping and fluid vein airtightness. The objective is to propose a characterization and a numerical modeling methodology that could easily be integrated within an industrial process. Nonlinearity characterization tests, based on the Restoring Force Surface method, are presented as well as viscoelastic characterization. Finally the proposed viscoelastic modeling, based on the Modal Strain Energy method, is validated against experimental data. [less ▲]

Detailed reference viewed: 34 (6 ULg)
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See detailDamping rates of hard momentum particles in a cold ultrarelativistic plasma
Vanderheyden, Benoît ULg; Ollitrault, J. Y.

in Physical Review. D : Particles and Fields (1997), 56(8), 5108-5122

We compute the damping rates of one-particle excitations in a cold ultrarelativistic plasma to leading order in the coupling constant e for three types of interaction: Yukawa coupling to a massless scalar ... [more ▼]

We compute the damping rates of one-particle excitations in a cold ultrarelativistic plasma to leading order in the coupling constant e for three types of interaction: Yukawa coupling to a massless scalar boson, QED, and QCD. Damping rates of charged particles in QED and QCD are of order e(3) mu, while the damping rates of other particles are of order e(4) mu or e(4) mu log(1/e). We find that the damping rate of an electron or of a quark is constant far from the Fermi surface, and decreases linearly with the excitation energy close to the Fermi surface. This unusual behavior is attributed to the long-range magnetic interactions. [less ▲]

Detailed reference viewed: 21 (5 ULg)