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See detailDam-break flow numerical modeling considering structural impacts on buildings
Erpicum, Sébastien ULg; Archambeau, Pierre ULg; Dewals, Benjamin ULg et al

in Proc. 33rd IAHR Congress: Water Engineering for a Sustainable Environment (2009)

Detailed reference viewed: 13 (2 ULg)
See detailDamage and fracture of ductile materials submitted to high strain rates. An implicit thermomechanically coupled approach with element erosion
Jeunechamps, Pierre-Paul ULg; Ponthot, Jean-Philippe ULg

in Proceedings of “PACAM XI, 11th Pan-American Congress of Applied Mechanics (2009)

Detailed reference viewed: 22 (0 ULg)
See detailDamage and fracture of materials submitted to high strain rates. A thermomechanically coupled approach with element erosion
Jeunechamps, Pierre-Paul ULg; Ponthot, Jean-Philippe ULg

in Proceedings of “Dynamic behaviour of materials”, Workshop in memory of Prof. J.R. Klepaczko (2009)

Detailed reference viewed: 11 (1 ULg)
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See detailDamage and Fracture of Materials Submitted to High Strain Rates. A Thermomechanically Implicit Coupled Approach with Element Erosion
Jeunechamps, Pierre-Paul; Boman, Romain ULg; Papeleux, Luc ULg et al

in Proceedings of the 3rd International Conference on Impact Loading of Lightweight Structures (2011, June 28)

Detailed reference viewed: 18 (8 ULg)
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See detailDamage and functional recovery of the Atlantic cod (Gadus morhua) inner ear hair cells following local injection of gentamicin
Faucher, Karine ULg; Aas-Hansen, Øyvind; Damsgård, Borge et al

in International Journal of Audiology (2009), 48(7), 456-464

This study addresses the ultrastructural and functional damage and subsequent recovery of the inner ear in the Atlantic cod following intrasaccular gentamicin injection. Inner ear damage was assessed ... [more ▼]

This study addresses the ultrastructural and functional damage and subsequent recovery of the inner ear in the Atlantic cod following intrasaccular gentamicin injection. Inner ear damage was assessed using SEM and measurements of AEP following 250-Hz pure-tone stimuli. Data from gentamicin-treated fish were compared with control (no injection) and sham (injection of saline) fish. Control fish had normal response thresholds associated with welldeveloped hair cell bundles in their macula sacculi. Sham fish had higher response thresholds compared with control fish during the first week post-intervention, but response thresholds were subsequently normal. Treated fish displayed significant inner ear damage associated with an increased average AEP threshold on the third day following treatment. Thereafter, inner ear tissue displayed signs of progressive regeneration until it was comparable to controls from the 14th day. Response thresholds were similar to those of control fish from the 17th day following treatment. These observations suggest that the macula sacculi of Atlantic cod can regenerate towards a near-complete functional and ultrastructural recovery within 17-21 days following ototoxic gentamicin treatment. [less ▲]

Detailed reference viewed: 31 (2 ULg)
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See detailDamage around tunnels in indurated clay: hydro-mechanical modelling aspects
Levasseur, Séverine ULg; Charlier, Robert ULg; Frieg, Bernd et al

in Li, Xiangling; Jing, Lanru; Blaser, Petra (Eds.) Impact of Thermo-Hydro-Mechanical-Chemical (THMC) processes on the safety of underground radioactive waste repositories (2009, September)

Detailed reference viewed: 23 (8 ULg)
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See detailA damage constitutive law for steel elevated temperature. Identification of the parameters
Castagne, Sylvie; Talamona, D.; Habraken, Anne ULg

in International Journal of Material Processing (2007), (1), 23-43

This paper presents a methodology of damage analysis at elevated temperature using the finite element method. Both the model and the methodology to identify parameters are summarized. The mechanical ... [more ▼]

This paper presents a methodology of damage analysis at elevated temperature using the finite element method. Both the model and the methodology to identify parameters are summarized. The mechanical properties are established using compression tests at elevated temperature. An elasto-visco-plastic model depending on temperature is identified. A metallographic analysis is used to determine the original size and morphology of the austenitic grains. The experimental damage analyses consist in acoustic tests in order to determine the apparition of the first crack during compression. Finite element simulations of these experiments allow the determination of the damage parameters using a reverse method. [less ▲]

Detailed reference viewed: 56 (8 ULg)
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See detailDamage detection and local resonances model in CFRP composite material by vibrothermography
Demy, Philippe ULg; Golinval, Jean-Claude ULg; Simon, Daniel

Scientific conference (2012, September)

Vibrothermography (VT) is an active non destructive technique able to detect singularities like delamination, even if the defect internal faces are in contact. Under sonic or ultrasonic mechanical ... [more ▼]

Vibrothermography (VT) is an active non destructive technique able to detect singularities like delamination, even if the defect internal faces are in contact. Under sonic or ultrasonic mechanical vibrations, a delamination may behave like a heat source principally due to friction between the rubbing faces and/or stress concentration in the area. The present article focuses on the understanding of the underlying phenomenon so-called "local resonances" and its correlation with the presence of temperature peaks observed at certain frequencies. For this purpose, a simplified finite element modal analysis of the delamination model is compared with the heating rate vs. frequency data's acquired by an infrared camera. Then, some conclusive results of sine sweep and chirp testing will be presented and discussed in regards to this theory. [less ▲]

Detailed reference viewed: 46 (12 ULg)
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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 ▲]

Detailed reference viewed: 22 (1 ULg)
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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 ▲]

Detailed reference viewed: 41 (6 ULg)
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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 ▲]

Detailed reference viewed: 83 (9 ULg)
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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 ▲]

Detailed reference viewed: 49 (8 ULg)
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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 ▲]

Detailed reference viewed: 135 (4 ULg)
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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)

Detailed reference viewed: 9 (0 ULg)
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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: 68 (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: 32 (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)
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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: 13 (2 ULg)