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See detailDamage Detection in Civil Engineering Structure Considering Temperature Effect
Nguyen, Viet Ha; Mahowald, Jean; Maas, Stefan et al

in Proceedings of IMAC XXXII Dynamics of Coupled Structures (2014, February)

This paper concerns damage identification of a bridge located in Luxembourg. Vibration responses were captured from measurable and adjustable harmonic swept sine excitation and hammer impact. Different ... [more ▼]

This paper concerns damage identification of a bridge located in Luxembourg. Vibration responses were captured from measurable and adjustable harmonic swept sine excitation and hammer impact. Different analysis methods were applied to the data measured from the structure showing interesting results. However, some difficulties arise, especially due to environmental influences (temperature and soil-behaviour variations) which overlay the structural changes caused by damage. These environmental effects are investigated in detail in this work. First, the modal parameters are identified from the response data. In the next step, they are statistically collected and processed through Principal Component Analysis (PCA) and Kernel PCA. Damage indexes are based on outlier analysis. [less ▲]

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See detailDamage detection in composites by vibrothermography and local resonances
Demy, Philippe ULg; Golinval, Jean-Claude ULg; Simon, Daniel

in Mechanics & Industry (2013), 14(2), 137-143

Vibrothermography is an active thermographic technique able to detect singularities like delamination in composite materials. Carbon fibre laminates are increasingly used, especially in aviation industry ... [more ▼]

Vibrothermography is an active thermographic technique able to detect singularities like delamination in composite materials. Carbon fibre laminates are increasingly used, especially in aviation industry where defect detection is directly related to safety. Physical causes of the internal heating mechanism linked to defect interaction with the elastic waves may be friction, viscoelastic hysteresis or plasticity. The method can efficiently detect flaws on complex geometries and only requires that both internal faces or edges are free to vibrate. The purpose of this work is to determine the relation between the observed heating right above a delamination by an IR camera and the frequency of a sinusoidal excitation between 8 and 27 kHz. The results clearly show specific heating peaks at certain frequencies. The comparison with local resonance frequencies of the delamination computed by simplified FEM shows similarities with the appearance of heating peaks. An experimental study having as goal to exploit the presence of those peaks and thus to increase the sensitivity of the method shows the interest for a high sweep sinusoidal excitation of the chirp type. The final objective of this research is to set up a serviceable short and reliable vibrothermographic test for non-destructive testing of composite materials. [less ▲]

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See detailDamage Detection in Structures Based on Principal Component Analysis of Forced Harmonic Responses
Golinval, Jean-Claude ULg

in Procedia Engineering (2017, September)

An approach based on principal component analysis (PCA) is considered here to tackle the problem of structural damage detection. The key idea of PCA is to reduce a large number of measured data to a much ... [more ▼]

An approach based on principal component analysis (PCA) is considered here to tackle the problem of structural damage detection. The key idea of PCA is to reduce a large number of measured data to a much smaller number of uncorrelated variables while retaining as much as possible of the variation in the original data. PCA is applied here to the problem of damage detection in structures submitted to harmonic excitation. When processing vibration measurements, it can be shown that the basis of eigenvectors (called the proper orthogonal modes) span the same subspace as the mode-shape vectors of the monitored structure. Thus the damage detection problem may be solved using the concept of subspace angle between a reference subspace spanned by the eigenvectors of the initial (undamaged) structure and the subspace spanned by the eigenvectors of the current (possibly damaged) structure. The method is illustrated on the example of a real truss structure for damage detection and is combined to a model updating technique for damage localization. [less ▲]

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See detailDamage Detection of Mechanical Components Using Null Subspace Analysis
Rutten, Christophe ULg; Loffet, Christophe; Golinval, Jean-Claude ULg

Conference given outside the academic context (2009)

This paper presents two original applications of the Null Subspace Analysis (NSA) method for fault diagnosis in mechanical components. The method is first applied to the case-study of electro-mechanical ... [more ▼]

This paper presents two original applications of the Null Subspace Analysis (NSA) method for fault diagnosis in mechanical components. The method is first applied to the case-study of electro-mechanical devices at the end of the assembly line with the aim of assessing their overall quality. The advantages of the proposed method rely in its rapidity of use and its reliability. At first, a set of five good (i.e. healthy) devices and four damaged devices was considered. The components were instrumented with one triaxial accelerometer on the flank and one monoaxial accelerometer on the top. Based on the NSA method, a mapping of the space [ active components, system order ] up to a system order of 100, was realized in order to select the appropriate order and number of active components. Eventually, thanks to this mapping, the method was able to successfully detect all the faulty components using the signal from only one accelerometer in one direction. The second application is related to the quality assessment of welded joints between stripes in a steel processing plan. Six welded joints with nominal welding parameters and twenty-seven welded joints with out-of-range parameters were realized. Again, the NSA method was able to diagnose successfully the welded joints using a single signal from one accelerometer. [less ▲]

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See detailDamage Detection on the Champangshiehl Bridge using Blind Source Separation
Nguyen, Viet Ha; Rutten, Christophe; Golinval, Jean-Claude ULg et al

in Strauss, Alfred; Frangopol, Dan M.; Bergmeister, Konrad (Eds.) Life-Cycle and Sustainability of Civil Infrastructure Systems (2012)

This paper addresses the problem of damage detection in civil engineering structures using characteristic subspaces obtained from principal component analysis (PCA) of output-only measurements. Damage ... [more ▼]

This paper addresses the problem of damage detection in civil engineering structures using characteristic subspaces obtained from principal component analysis (PCA) of output-only measurements. Damage detection is performed by comparing subspace features between a reference (healthy) state and a current (possibly damaged) state. The damage indicator used in this study is the angular coherence between sub-spaces. The considered damage detection procedure is illustrated on the Champangshiehl Bridge which is a two span concrete box girder bridge located in Luxembourg. Before its destruction, multiple damage levels were inten-tionally created by cutting a growing number of prestressed tendons. Vibration data were acquired by the University of Luxembourg for each damaged state at many locations on the bridge. As previous studies dem-onstrated the large importance of environmental factors on modal identification, special care was taken to evaluate this influence during the test campaign. [less ▲]

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See detailDamage Detection Using Blind Source Separation Techniques
Nguyen, Viet Ha ULg; Golinval, Jean-Claude ULg

in IMAC-XXIX: Conference & Exposition on Structural Dynamics - Advanced Aerospace Applications (2011)

Blind source separation (BSS) techniques are applied in many domains since they allow separating a set of signals from their observed mixture without the knowledge (or with very little knowledge) of the ... [more ▼]

Blind source separation (BSS) techniques are applied in many domains since they allow separating a set of signals from their observed mixture without the knowledge (or with very little knowledge) of the source signals or the mixing process. Two particular BSS techniques called Second-Order Blind Identification (SOBI) and Blind Modal Identification (BMID) are considered in this paper for the purpose of structural damage detection or fault diagnosis in mechanical systems. As shown on experimental examples, the BMID method reveals significant advantages. In addition, it is demonstrated that damage detection results may be improved significantly with the help of the block Hankel matrix. The main advantage in this case is that damage detection still remains possible when the number of available sensors is small or even reduced to one. Damage detection is achieved by comparing the subspaces between the reference (healthy) state and a current state through the concept of subspace angle. The efficiency of the methods is illustrated using experimental data. [less ▲]

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See detailDamage Detection Using Model Updating and Identification Techniques
Pascual, Rodrigo; Trendafilova, Irina; Golinval, Jean-Claude ULg et al

Conference given outside the academic context (1999)

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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 ▲]

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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 ▲]

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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 ▲]

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See detailDamage mechanics model for the initiation life of stress corrosion cracking
Wu, Ling ULg; Chen, ZhaoTao; Sun, Qin

in Journal of Mechanical Strength = Ji Xie Qiang Du (2004), 26(Suppl.), 58-59

The problem of stress corrosion cracking initiation has been studied on the base of continuum damage mechanics. The attack of load together with environment will weaken the materials, and the degree of ... [more ▼]

The problem of stress corrosion cracking initiation has been studied on the base of continuum damage mechanics. The attack of load together with environment will weaken the materials, and the degree of the weakening can be described well by the damage variable used in damage mechanics.Just as the use of the damage mechanics in predicting the initiation life for creep and fatigue cracks, a stress-corrosion damage evolvement model , which has considered the roles of the threshold stress , effective stress and the existed damage, is established. And the effects of the environment corrosion are presented with the parameters in the evolvement model. Then a stress-corrosion crack initiation life model is deduced from the damage evolvement model with the concept of the damage accumulation. The initiation lives of the stress corrosion cracking have been predicted for two kinds of materials at different stress levels .The predicted results show a good agreement with the testing results. [less ▲]

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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: 15 (2 ULg)
See detailDamage Model Identification Using Inverse Problem Methodology
Kleinermann, Jean-Pascal; Ponthot, Jean-Philippe ULg; Stainier, Laurent ULg

in proceedings of Plasticity’2000 (2000)

Detailed reference viewed: 40 (2 ULg)
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See detailDamage modeling of composites and reliability analysis
Zein, Samih; Bruyneel, Michaël ULg

in Proceeding of the ESTEC European Conference on Spacecraft Structures, Materials and Environmental Testing 2014 (2014, April)

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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)

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See detailDamage modeling of laminated composites : validation of the intra-laminar damage law of SAMCEF at the coupon level for UD plies
Bruyneel, Michaël ULg; Delsemme, Jean-Pierre; Goupil, Anne-Charlotte et al

in proceedings of the European Conference on Composite Material, ECCM16 (2014, June)

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See detailDamage modeling of laminated composites: validation of the inter-laminar damage law of SAMCEF at the coupon level for UD plies
Bruyneel, Michaël ULg; Delsemme, Jean-Pierre; Goupil, Anne-Charlotte et al

in E. Oñate, J. Oliver and A. Huerta (Ed.) Proceedings of the 11th World Congress on Computational Mechanics (WCCM XI) (2014, July)

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See detailDamage modeling of woven-fabric laminates with SAMCEF: validation at the coupon level
Bruyneel, Michaël ULg; Delsemme, Jean-Pierre; Goupil, Anne-Charlotte et al

in Proceedings of the International Conference on Advanced Computational Methods in Engineering – ACOMEN 2014 (2014, June)

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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 ▲]

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See detailDamage modelling of composites: validation of inter-laminar damage model at the element level
Bruyneel, Michaël ULg; Deslemme, Jean-Pierre; Jetteur, Philippe et al

Article for general public (2014)

Detailed reference viewed: 24 (0 ULg)