References of "Georges, Marc"
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See detailCombined holography and thermography in a single sensor through image-plane holography at thermal infrared wavelengths
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Optics Express (2014), 22(21), 25517-25529

Holographic interferometry in the thermal wavelengths range, combining a CO2 laser and digital hologram recording with a microbolometer array based camera, allows simultaneously capturing temperature and ... [more ▼]

Holographic interferometry in the thermal wavelengths range, combining a CO2 laser and digital hologram recording with a microbolometer array based camera, allows simultaneously capturing temperature and surface shape information about objects. This is due to the fact that the holograms are affected by the thermal background emitted by objects at room temperature. We explain the setup and the processing of data which allows decoupling the two types of information. This natural data fusion can be advantageously used in a variety of nondestructive testing applications. [less ▲]

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See detailImprovement of defect detection in shearography by using Principal Component Analysis
Vandenrijt, Jean-François ULg; Lièvre, Nicolas; Georges, Marc ULg

in Proceedings of Conference on Interferometry XVII: Techniques and Analysis (2014, August)

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See detailVibration analysis by speckle interferometry with CO2 lasers and microbolometers arrays
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Georges, Marc ULg

in OSA Technical Digest (online) (2014, July)

Speckle interferometry in the time-average mode in long wave infrared is shown for observing the mode shapes of vibrating objects. The long wavelength allows observing larger vibration displacements than ... [more ▼]

Speckle interferometry in the time-average mode in long wave infrared is shown for observing the mode shapes of vibrating objects. The long wavelength allows observing larger vibration displacements than what is achieved with visible wavelengths. [less ▲]

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See detailLong-wave infrared digital holographic interferometry with diffuser or point source illuminations for measuring deformations of aspheric mirrors
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Queeckers, Patrick et al

in Optical Engineering : The Journal of the Society of Photo-Optical Instrumentation Engineers (2014), 53(11), 112309

Long-wave infrared digital holographic interferometry with CO2 laser and microbolometer arrays has been developed for testing the large deformations of space reflectors. The setup considered is a ... [more ▼]

Long-wave infrared digital holographic interferometry with CO2 laser and microbolometer arrays has been developed for testing the large deformations of space reflectors. The setup considered is a Mach–Zehnder, associated to the digital holography reconstruction of the wavefront in the inline configuration with phase shifting. Two possibilities exist for illuminating the tested reflector: either with a point source (similarly to classical interferometry) or an extended source (with a diffuser). This paper presents the development of a modular setup which allows comparing both in the case of a parabolic mirror [less ▲]

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See detailInfrared Holography
Georges, Marc ULg

Scientific conference (2014, April 11)

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See detailSimultaneous Temperature and Deformations Measurements Using Long-Wave Infrared Speckle Interferometry: A Novel Hybrid Technique for Industrial Nondestructive Testing
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

in Osten, Wolfgang (Ed.) Fringe 2013 (2014)

The use of long-wave infrared (LWIR) CO2 lasers and microbolometer arrays in digital holographic and speckle interferometry shows interesting features for full-field displacement/deformation metrology and ... [more ▼]

The use of long-wave infrared (LWIR) CO2 lasers and microbolometer arrays in digital holographic and speckle interferometry shows interesting features for full-field displacement/deformation metrology and nondestructive testing. The first one is that the long wavelength yields the measurement of larger displacements together with decreasing the sensitivity to environmental perturbations. Therefore these interferometric methods can be applied more easily in industrial field applications. Another advantage was put forward in the European project FANTOM which is presented in this paper. In addition to specklegrams, the thermal background is captured simultaneously. Therefore in displacement metrology one can correlate uniquely the temperature and displacement information at the same time and in each pixel. We describe the successful achievements of the project. Thorough understanding of optics and speckle interferometry crossed with state-of-art in thermam imaging systems allowed to study this new hybrid technique in deep and tackle some specific constraints for reaching the best performances. As a result, a mobile instrument has been developed and validated on various industrial structural testing facilities and inspection areas. It has been used in thermomechanical measurements as well as in detection of defects in aeronautical composites. In particular we show that the two parts of the signal (the thermal part on one hand and the interferograms showing the deformation on the other hand) yield complementary information. A very interesting result is that it allows increasing the probability of detecting defects, for some of them are better seen in the thermal signal, whereas others appear only through local surface deformation. [less ▲]

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See detailDigital Holographic Interferometry in the Long-Wave Infrared for the Testing of Large Aspheric Space Reflectors
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Stockman, Yvan ULg et al

in Osten, Wolfgang (Ed.) Fringe 2013 (2014)

Digital holographic (DH) interferometry has been developed in the long-wave infrared spectral range with CO2 lasers and microbolometer arrays. This application has been driven by the European Space ... [more ▼]

Digital holographic (DH) interferometry has been developed in the long-wave infrared spectral range with CO2 lasers and microbolometer arrays. This application has been driven by the European Space Agency’s constant need of techniques for monitoring large displacements of large structures. Here the study focuses on the case of aspheric mirrors, like parabola and ellipses. Usually they are tested through interferometric wavefront error measurements which require expensive null-lenses matching each of the reflectors considered. In the case of monitoring deformation a holographic technique can be considered where the wavefront is compared with itself at different instant. Therefore the optical can be quite simple and easily reconfigurable from one reflector to another. The advantage of using long wavelength is that large deformations can be measured at once, in addition to being more immune against environmental perturbations. Another advantage of DH at such wavelengths is that the ratio between the wavelength and the pixel size allows reconstructing objects 5 to 10 times larger than with DH in the visible. In this project we considered first the case of a 1.1 meter diameter parabola for submillimeter range observations. Such specimen shows strong specular reflectivity. We have developed several set-ups with different ways to illuminate the object and to collect rays to form the object beam: either through point source or through and extended diffuser working by reflection of the laser beam. Both possibilities have been compared in terms of fringe quality as well as measurement range. We selected the diffuser illumination for applying the set-up into a large vacuum facility for measuring the deformation of the parabola between 224 and 107 K. Results of this measurement campaign are presented. A further application has been shown by observation of off-axis ellipse. In this case interferometric testing is difficult to achieve and LWIR DHI with diffuser illumination is found quite simple to implement and gives straightforward results. [less ▲]

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See detailAutomated Defect Detection Algorithm Applied to Shearography in Composites
Vandenrijt, Jean-François ULg; Georges, Marc ULg

in Osten, Wolfgang (Ed.) Fringe 2013 (2014)

The aeronautic industry is progressively introducing composite material in its products. Nowadays the fabrication begins to be mature, but huge efforts remains to be done on the experimental validation of ... [more ▼]

The aeronautic industry is progressively introducing composite material in its products. Nowadays the fabrication begins to be mature, but huge efforts remains to be done on the experimental validation of these materials. More specifically, these composite materials introduce new type of defects (such as delamination, glue defects…) which need to be detected during the fabrication and maintenance to prevent failures. Moreover, the widespread use of these materials impose to the future detection instruments to be cheap, robust and easy to manipulate by non-specialists. Currently shearography is widely used for the detection of defects in the composite material. It is cheap, and relatively robust and flexible, but requires special qualification to interpret the shearograms and identify the defects. Therefore, efforts need to be carried to ease the interpretation of stereographic results for non-specialist of the technique. For this, we propose to automate the identification of defects in shearograms by the development of specific algorithms. In this paper, we present an innovative algorithm which realizes this operation. The process inspects the wrapped phase map obtained to identify high local fringe density. These potential detects are then analyzed and selected based on a set of parameter criteria such as dimensions, shape, and detection threshold. Successful results obtained on thermally solicited composite sample observed in industrial conditions are shown. We also discuss the limitations and perspective of this approach. [less ▲]

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See detailPerformances of Volume Phase Holographic grating for space applications: study of the radiation effect
Loicq, Jerôme ULg; Georges, Marc ULg; Stockman, Yvan ULg et al

in Applied Optics (2013), 52(34),

The special properties of volume phase holographic gratings make them promising candidates for spectrometry applications where high spectral resolution, low levels of straylight, and low polarization ... [more ▼]

The special properties of volume phase holographic gratings make them promising candidates for spectrometry applications where high spectral resolution, low levels of straylight, and low polarization sensitivity are required. Therefore it is of interest to assess the maturity and suitability of volume phase holographic gratings as enabling technologies for future space missions, with demanding requirements for spectrometry. One of the main areas of research is related to grating ageing under space radiation. In the present paper, two volume grating technologies are analyzed and compared under gamma irradiation. The performances of both technologies, the photo–thermo–refractive glass and the Dichromated Gelatin, are tested on samples and assessed in the and near-infrared bands. The diffraction efficiency degradation under gamma irradiation is assessed. [less ▲]

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See detailComparaison de techniques CND émergentes sur des pièces aéronautiques en matériaux composites
Georges, Marc ULg; Thizy, Cédric ULg; Lewandowski, Jacques et al

Conference (2013, November)

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See detailReview of thermal imaging systems in composite defect detection
Jorge, Iagoba; Venegas, Pablo; Vega, Laura et al

in Infrared Physics & Technology (2013), 61

Thermal imaging technologies are widely used at present in many industrial areas, while being nowadays more and more employed in R&D&i activities. This article focuses on the comparison of the results ... [more ▼]

Thermal imaging technologies are widely used at present in many industrial areas, while being nowadays more and more employed in R&D&i activities. This article focuses on the comparison of the results obtained with commercially available non-experimental infrared (IR) cameras in the field of non-destructive defect detection. One of the cameras belongs to the FLIR SC5000 series, which is a medium wavelength infrared (MWIR) camera, and the other two cameras are from the high-end ImageIR series manufactured by InfraTec GmbH: The ImageIR 8300 also belongs to the class of MWIR cameras and the ImageIR 8800 is a long wavelength infrared (LWIR) camera. The comparative study is carried out by means of inspecting three different calibrated and induced defect samples with these three cameras using similar excitation sources, so that the configuration and lay out of the tests are comparable with each other. Additionally, after every inspection, a mathematical post-processing is applied to the resulting raw thermal images in order to enhance the detection of defects present in the samples. [less ▲]

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See detailComparison of 3 emerging optical NDI techniques on complex shaped composite structures based on carbon fiber
Georges, Marc ULg

Conference (2013, October 01)

Thermography, shearography and laser ultrasonics are 3 contactless emerging techniques which allow nondestructive inspection of composite structures. Thermography and shearography are full-field ... [more ▼]

Thermography, shearography and laser ultrasonics are 3 contactless emerging techniques which allow nondestructive inspection of composite structures. Thermography and shearography are full-field techniques yielding measurement of respectively local temperature variations or deformations of a structure undergoing a stress (thermal, pressure, vibration). Laser ultrasonics allows remote ultrasound generation in the composite by thermoelastic effect followed by remote measurement of the surface displacements under the effect of the ultrasound echoes without coupling. This point-like technique requires scanning. The three techniques have been selected in our project since they allow inspection of complex shaped parts. We present compared results obtained on a variety of aeronautical industrial composite parts. [less ▲]

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See detailMobile speckle interferometer in the long-wave infrared for aeronautical nondestructive testing in field conditions
Vandenrijt, Jean-François ULg; Thizy, Cédric ULg; Alexeenko, Igor et al

in Optical Engineering : The Journal of the Society of Photo-Optical Instrumentation Engineers (2013), 52(10),

Abstract We present the development of a speckle interferometer based on CO2 laser and using a thermal infrared camera based on uncooled microbolometer array. It is intended to be used for monitoring ... [more ▼]

Abstract We present the development of a speckle interferometer based on CO2 laser and using a thermal infrared camera based on uncooled microbolometer array. It is intended to be used for monitoring deformations as well as flaw detection in aeronautical composites, with a smaller sensitivity to displacement compared to equivalent system using visible lasers. Moreover the long wavelength allows working with such interferometer under out-of-laboratory conditions. A mobile system has been developed on the basis of previous laboratory developments. Then it is validated in a variety of industrial nondestructive testing applications under field working conditions. [less ▲]

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See detailComparison of three NDT techniques for the inspection of aeronautic composite structures
Dubé, Robin; Scheed, Laurent; Lewandoswki, Jacques et al

Conference (2013, July 28)

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See detailDigital Holographic Interferometry with CO2 Lasers Applied to Aspheric Space Reflectors Testing
Georges, Marc ULg; Vandenrijt, Jean-François ULg; Thizy, Cédric ULg et al

Conference (2013, May)

Digital holographic interferometry at long infrared wavelengths allows monitoring large deformations of space reflectors during vacuum-thermal testing. We present different optical schemes and an ... [more ▼]

Digital holographic interferometry at long infrared wavelengths allows monitoring large deformations of space reflectors during vacuum-thermal testing. We present different optical schemes and an application to the complex case of elliptic reflector. [less ▲]

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See detailHolographic interferometry based on photorefractive crystal to measure 3D thermo-elastic distortion of composite structures and comparison with finite element models
Thizy, Cédric ULg; Eliot, F.; Olympio, K.R. et al

in Lehmann, Peter (Ed.) Proc. SPIE Vol 8788 on Optical Measurement Systems for Industrial Inspection VIII (2013, May)

Thermo-elastic distortions of composite structures have been measured by a holographic camera using a BSO photorefractive crystal as the recording medium. The first test campaign (Phase 1) was performed ... [more ▼]

Thermo-elastic distortions of composite structures have been measured by a holographic camera using a BSO photorefractive crystal as the recording medium. The first test campaign (Phase 1) was performed on CFRP struts with titanium end-fittings glued to the tips of the strut. The samples were placed in a vacuum chamber. The holographic camera was located outside the chamber and configured with two illuminations to measure the relative out-of-plane and in-plane (in one direction) displacements. The second test campaign (Phase 2) was performed on a structure composed of a large Silicon Carbide base plate supported by 3 GFRP struts with glued Titanium end-fittings. Thermo-elastic distortions have been measured with the same holographic camera used in phase 1, but four illuminations, instead of two, have been used to provide the three components of displacement. This technique was specially developed and validated during the phase 2 in CSL laboratory. The system has been designed to measure an object size of typically 250x250 mm²; the measurement range is such that the sum of the largest relative displacements in the three measurement directions is maximum 20 μm. The validation of the four-illuminations technique led to measurement uncertainties of 120 nm for the relative in-plane and out-of-plane displacements, 230 nm for the absolute in-plane displacement and 400 nm for the absolute out-of-plane displacement. For both campaigns, the test results have been compared to the predictions obtained by finite element analyses and the correlation of these results was good [less ▲]

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See detailEvaluation de technologies émergentes pour le contrôle non destructif de composites aéronautiques
Georges, Marc ULg; Lewandowski, Jacques

Scientific conference (2013, March 13)

La proportion des pièces en composite utilisées dans les structures des aéronefs ne cesse de croître, posant de nouveaux défis techniques et économiques aux méthodes de contrôle non destructif (CND ... [more ▼]

La proportion des pièces en composite utilisées dans les structures des aéronefs ne cesse de croître, posant de nouveaux défis techniques et économiques aux méthodes de contrôle non destructif (CND) classiquement utilisées: géométries complexes, larges surfaces à inspecter, impossibilité d’immerger certains composants. La thermographie infrarouge, la shearographie et le laser-ultrasons sont des techniques émergentes encore assez peu répandues dans l’industrie, mais qui présentent un fort potentiel vis-à-vis de ces nouvelles problématiques. Cet atelier présentera ces trois techniques en s’appuyant sur des résultats d’inspection sur des pièces aéronautiques variées: bord d’attaque, raidisseur en Omega, secteur de virole, plancher complexe avec raidisseurs. Ces résultats sont le fruit d’une collaboration entre le Centre spatial de Liège (Belgique), le Centro de Tecnologias Aeronauticas (Espagne) et le Centre technologique en aérospatiale (Canada). [less ▲]

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See detailTests non-destructifs (NDT) pour structures en matériaux composites
Georges, Marc ULg

Scientific conference (2013, February 28)

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