References of "Georges, Marc"
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See detailThermography-inspired processing strategy applied on shearography towards nondestructive inspection of composites
Kirkove, Murielle ULiege; Zhao, Yuchen ULiege; Blain, Pascal ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2019, June 21), 11056

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See detailShearography inspection of monolithic CFRP composites: finite element modeling approach for assessing an adequate strategy of artificial defects representing delamination
Vandenrijt, Jean-François ULiege; Xiong, Hu; Lequesne, Cédric et al

in Proceedings of SPIE: The International Society for Optical Engineering (2019, June 21), 11056

Delamination in carbon fiber reinforced polymer (CFRP) laminated composites is an important problem for industry. Nondestructive inspection (NDI) methods aim at locating such defects. Shearography is a ... [more ▼]

Delamination in carbon fiber reinforced polymer (CFRP) laminated composites is an important problem for industry. Nondestructive inspection (NDI) methods aim at locating such defects. Shearography is a full-field NDI method that could be considered to detect them. Reference plates for assessing performances of NDI methods for detecting delamination use artificial defects of several types introduced in reference CFRP matrices. Although they are standardized for usual ultrasound testing, these artifacts are not necessarily adequate for shearography. We have studied this problem by comparing shearography experiment and simulations by finite element analysis. We show the convergence with experiments on the case of flat bottom hole artifacts. Then we discuss the adequateness of other artifacts through simulations. [less ▲]

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See detailAccurate π/2-phase shifting setup for a stabilized interference pattern of light fringes
de Oliveira, Ivan; Borges Bertasso, Flavio; Georges, Marc ULiege et al

in Optik - International Journal for Light and Electron Optics (2019), 178

We report on a technique for accurately π/2-phase shifting a stabilized interference pattern of light fringes used for building up a map of phase for 2D deformation measurement. This technique is based on ... [more ▼]

We report on a technique for accurately π/2-phase shifting a stabilized interference pattern of light fringes used for building up a map of phase for 2D deformation measurement. This technique is based on the use of low amplitude phase modulation on the setup in order to generate first and second harmonics temporal terms in the pattern of light to operate an actively stabilized setup. Particular features of this stabilization setup allow one to use them for accurate π/2-phase shifting with the practical advantage of operating on an already stabilized pattern of fringes. [less ▲]

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See detailDetermination of vibration amplitudes from binary phase patterns obtained by phase-shifting time-averaged speckle shearing interferometry
Kirkove, Murielle ULiege; Guérit, Stéphanie; Jacques, Laurent et al

in Applied Optics (2018), 57(27), 8065-8077

Speckle shearing interferometry (shearography) is a full-field strain measurement technique that can be used in vibration analysis. In our case, we apply a method that combines the time-averaging and ... [more ▼]

Speckle shearing interferometry (shearography) is a full-field strain measurement technique that can be used in vibration analysis. In our case, we apply a method that combines the time-averaging and phase-shifting tech- niques. It produces binary phase patterns, where the phase changes are related to the zeroes of a Bessel J 0 function, typical of time-averaging. However, the contrast and resolution are better compared to traditional time-averaging. In a previous paper, we have shown that this is particularly useful in vibration testing performed under industrial conditions, because fringe patterns are noisier than in quiet laboratory environments. This paper goes a step further in proposing a processing method for estimating the vibration amplitude, for helping non-experts to identify vibration modes. Since shearography measures the spatial derivative of displacement, spatial integration is required. Prior to that, different processes like denoising, binarization, automated nodal line detection, and amplitude assignment are applied. We analyze the performance of the method on synthetic and experimental data, in the function of noise level and fringes density. Results on data acquired in an industrial environment illustrate the good performances of the proposed method. [less ▲]

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See detailMechanical deformations of space mirrors under thermal stress and their effect on wavefront errors: measurements by ESPI and comparison with multiphysics modeling
Languy, Fabian ULiege; Vandenrijt, Jean-François ULiege; Saint-Georges, Philippe et al

in Proceedings of SPIE: The International Society for Optical Engineering (2018, September 07), 10834

Numerical modeling tools are widely used in space science, but are usually limited to the thermomechanical steps. However, many payloads are equipped with high performance optical systems with tight ... [more ▼]

Numerical modeling tools are widely used in space science, but are usually limited to the thermomechanical steps. However, many payloads are equipped with high performance optical systems with tight tolerances. Therefore, experimental testing of space optics in very realistic conditions is a mandatory process. This experimental step is both time consuming and expensive. A multiphysics modeling tool that also takes into account the optical performances would therefore be an elegant solution to avoid these drawbacks. In this paper we compare some experimental results with numerical results obtained from a multiphysics suite. The local displacements of two space mirrors have been measured by use of electronic speckle pattern interferometry (ESPI) and the deformation itself has been calculated by subtracting the rigid body motion. After validation of the thermo-mechanical model, experimental and numerical wavefront errors are compared. [less ▲]

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See detailProcessing of binary fringe patterns obtained by phase-shifting time-averaged shearography on vibrating objects
Kirkove, Murielle ULiege; Guérit, Stéphanie; Jacques, Laurent et al

in Jaroszewicz, L. R. (Ed.) Proceedings of SPIE volume 10834, 7th International Conference on Speckle Metrology, Speckle 2018 (2018, September 07)

Shearography can be used for full-field strain measurements in the field of vibration analysis. It provides the spatial derivative of the optical phase difference of the vibration modes amplitude along ... [more ▼]

Shearography can be used for full-field strain measurements in the field of vibration analysis. It provides the spatial derivative of the optical phase difference of the vibration modes amplitude along the so-called shear direction. The shearographic setup considered here is based on the phase-shifting time-averaged technique. It can easily be applied experimentally, but its drawback is that binary phase patterns are obtained. These phase changes are related to the zeroes of a Bessel function. Retrieving the corresponding displacement maps is not straightforward. Moreover, integration of shearographic results need to be performed, and this step is sensitive to noise in the patterns. In this paper, different processing stages are described, from fringe denoising to integration of the displacement maps. The application on data acquired in industrial environment illustrates the good performances of the proposed method. [less ▲]

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See detailSpace mirror deformation: from thermo- mechanical measurements by speckle interferometry to optical comparison with multiphysics simulation
Languy, Fabian ULiege; Vandenrijt, Jean-François ULiege; Saint-Georges, Philippe et al

in Applied Optics (2018), 57(24), 6982

Experimental testing of space optics is a mandatory process for investigating the optical performances in conditions close to reality. With the optical requirement level increasing over years, these ... [more ▼]

Experimental testing of space optics is a mandatory process for investigating the optical performances in conditions close to reality. With the optical requirement level increasing over years, these experimental tests are increasingly expensive and time-consuming. A modeling tool would therefore be an elegant solution to avoid these drawbacks. For this purpose, a multiphysics approach has been used to predict how optics behave under thermal loads. In this paper, experimental surface deformations of a space mirror perturbed by thermal gradients are compared to multiphysics simulation results. The local displacements of the mirror surface have been measured by use of electronic speckle pattern interferometry, and the deformation itself has been calculated by subtracting the rigid body motion. After validation of the thermo-mechanical solution, experimental and numerical wavefront errors are compared. [less ▲]

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See detailDigital Holographic Interferometry in the Long-Wave Infrared Range for Measuring Large Deformations of Space Components under Thermal-Vacuum Testing
Vandenrijt, Jean-François ULiege; Thizy, Cédric ULiege; Languy, Fabian ULiege et al

in Proceedings (2018, July 09), 2018(2), 534

Holographic interferometry at around 10 µm wavelengths has many advantages. It offers the possibility of large deformation measurement, while being much less sensitive to external perturbations. We ... [more ▼]

Holographic interferometry at around 10 µm wavelengths has many advantages. It offers the possibility of large deformation measurement, while being much less sensitive to external perturbations. We present the state-of-the art of this technique applied to several industrial cases of the space industry. In particular, we demonstrate that the technique is well adapted to measurement of full-field deformation maps of space structures undergoing large temperature variations typical to what they experience in space conditions. [less ▲]

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See detailLaser ultrasound flexible system for non-contact inspection of medium size and complex shaped composite structures made of carbon fiber reinforced polymer
Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege; Thizy, Cédric ULiege et al

in Proceedings (2018, June 22), 2018(2), 455

We present the development of a contactless laser ultrasound system for nondestructive inspection of CFRP complex structures. Ultrasound are generated by a thermoelastic effect resulting from a green ... [more ▼]

We present the development of a contactless laser ultrasound system for nondestructive inspection of CFRP complex structures. Ultrasound are generated by a thermoelastic effect resulting from a green pulsed laser insulating a point of the inspected part. The resulting displacement of the surface point is probed by a two-wave mixing based interferometer working in the near infrared. The system is flexible and completely fiber-coupled. It is able to provide C-scans on complex shaped CFRP aeronautical structures. [less ▲]

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See detailThermography and Shearography Inspection of Composite Hybrid Sandwich Structure Made of CFRP and GFRP Core and Titanium Skins
Georges, Marc ULiege; Srajbr, Christian; Menner, Philipp et al

in Proceedings (2018, June 22), 2018(2), 484

We have investigated several full-field contactless techniques, such as thermography and shearography, with several excitation methods for inspecting hybrid composite-metal sandwich structures. The latter ... [more ▼]

We have investigated several full-field contactless techniques, such as thermography and shearography, with several excitation methods for inspecting hybrid composite-metal sandwich structures. The latter are made of a core with epoxy reinforced by carbon and glass fibers and skins of titanium. Several calibrated defects are incorporated at different places in depth and are made of air gaps and inserts. [less ▲]

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See detailFocal plane detection via holographic autofocusing criterion applied on Terahertz TDS system
Zhao, Yuchen ULiege; Nguyen, D. T.; Hermandez, Y. et al

in Imaging and Applied Optics 2018 (3D, AO, AIO, COSI, DH, IS, LACSEA, LS&C, MATH, pcAOP) (2018, June)

Holographic autofocusing technique is applied on a terahertz time-domain spectroscopy system to improve focus accuracy. We experimentally perform the focus plane detection with TDS measurement. Amplitude ... [more ▼]

Holographic autofocusing technique is applied on a terahertz time-domain spectroscopy system to improve focus accuracy. We experimentally perform the focus plane detection with TDS measurement. Amplitude and phase information at different wavelengths are extracted. [less ▲]

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See detailImagerie Terahertz pour l’inspection des composites
Georges, Marc ULiege; Zhao, Yuchen ULiege

Conference given outside the academic context (2018)

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See detailDigital holographic interferometry application on objects with heterogeneous reflecting properties
Vandenrijt, Jean-François ULiege; Zhao, Yuchen ULiege; Languy, Fabian ULiege et al

in Optics InfoBase Conference Papers (2018), Part F100-DH 2018

Some objects of industrial interest show zones which can be either scattering or specular. We present experimental digital holographic interferometry results obtained in a setup dealing with both at the ... [more ▼]

Some objects of industrial interest show zones which can be either scattering or specular. We present experimental digital holographic interferometry results obtained in a setup dealing with both at the same time. [less ▲]

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See detailThermal infrared and terahertz digital holography and their applications
Georges, Marc ULiege

Scientific conference (2017, October 03)

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See detailPractical simulation of delamination in composites for thermography NDT
Théroux, Louis-Daniel; Lewandowski, Jacques; Masson, Benoit et al

Conference (2017, September)

This paper tackles the issue of simulating delaminations in reference standards made of CFRP (carbon fiber reinforced polymer) used for non-destructive testing by thermography. Thermography results of a ... [more ▼]

This paper tackles the issue of simulating delaminations in reference standards made of CFRP (carbon fiber reinforced polymer) used for non-destructive testing by thermography. Thermography results of a real delamination are compared with flat bottom holes with similar size and depth. Results show a notable difference of the thermal contrast between the real delaminations and the FBH. To replicate the thermal behavior of a real delamination, a solution is proposed by plugging the flat-bottom hole. Thermography tests were conducted with plugs using various materials with thermal properties similar to CFRP. [less ▲]

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See detailDeformation measurements by ESPI of the surface of a heated mirror and comparison with numerical model
Languy, Fabian ULiege; Vandenrijt, Jean-François ULiege; Saint-Georges, Philippe et al

in Proceedings of SPIE: The International Society for Optical Engineering (2017, June 26), 103291M

The manufacture of mirrors for space application is expensive and the requirements on the optical performance increase over years. To achieve higher performance, larger mirrors are manufactured but the ... [more ▼]

The manufacture of mirrors for space application is expensive and the requirements on the optical performance increase over years. To achieve higher performance, larger mirrors are manufactured but the larger the mirror the higher the sensitivity to temperature variation and therefore the higher the degradation of optical performances. To avoid the use of an expensive thermal regulation, we need to develop tools able to predict how optics behaves with thermal constraints. This paper presents the comparison between experimental surface mirror deformation and theoretical results from a multiphysics model. The local displacements of the mirror surface have been measured with the use of electronic speckle pattern interferometry (ESPI) and the deformation itself has been calculated by subtracting the rigid body motion. After validation of the mechanical model, experimental and numerical wave front errors are compared. [less ▲]

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See detailNondestructive inspection of aerospace composites by a fiber-coupled laser ultrasonics system
Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege; Thizy, Cédric ULiege et al

in Proceedings of SPIE: The International Society for Optical Engineering (2017, June)

Laser ultrasonics is a technique currently studied for nondestructive inspection of aerospace composite structures based on carbon fibers. It combines a pulsed laser impacting the surface generates an ... [more ▼]

Laser ultrasonics is a technique currently studied for nondestructive inspection of aerospace composite structures based on carbon fibers. It combines a pulsed laser impacting the surface generates an ultrasound inside the material, through the nondestructive thermoelastic effect. Second a detection interferometer probes the impacted point in order to measure the displacement of the surface resulting from the emitted ultrasound wave and the echo coming back from the different interfaces of the structure. Laser ultrasonics is of interest for inspecting complex shaped composites. We have studied the possibility of using frequency doubled YAG laser for the generation and which is fiber-coupled, together with a fiber-coupled interferometric probe using a YAG laser in the NIR. Our final system is a lightweight probe attached to a robot arm and which is able to scan complex shapes. The performances of the system are compared for different wavelengths of generations. Also we have studied some experimental parameters of interest such as tolerance to angle and focus distance, and different geometries of generation beams. We show some examples of inspection of reference parts with known defects. In particular C-scans of curved composites structures are presented. [less ▲]

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See detailAccuracy improvement in digital holographic-based speckle correlation for three-dimensional (3D) displacement measurement
Zhao, Yuchen ULiege; Zemmamouche, Redouane; Vandenrijt, Jean-François ULiege et al

in Digital Holography and Three-Dimensional Imaging (2017, June)

Combination of digital holography and speckle correlation for three-dimensional displacement measurement suffers from inaccuracy. Speckle size adjustment and phase error correction during the digital ... [more ▼]

Combination of digital holography and speckle correlation for three-dimensional displacement measurement suffers from inaccuracy. Speckle size adjustment and phase error correction during the digital holography process can improve the accuracy of in-plane displacement measurement. [less ▲]

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See detailArtificial defects in CFRP composite structure for Thermography and Shearography nondestructive inspection
Blain, Pascal ULiege; Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege et al

in Proceedings of SPIE 10449, Fifth International Conference on Optical and Photonics Engineering (2017, April)

Locating defects in CFRP composite materials is a hot topic in nondestructive inspection (NDI). Beside classical NDI technique, such as ultrasound testing (UT), contactless techniques are actively studied ... [more ▼]

Locating defects in CFRP composite materials is a hot topic in nondestructive inspection (NDI). Beside classical NDI technique, such as ultrasound testing (UT), contactless techniques are actively studied. Generally manufacturers of CFRP structure incorporate artificial defects in the bulk, with different extents and depths, in order to study the performance of a specific NDI technique to detect the defect. One of the most common defects in CFRP is delamination between two layers. This is simulated by inserting teflon sheets which, like air, acts as ultrasound blocker in UT. When such reference part is used to assess NDI performance of thermography or shearography, we only observe respectively the thermal or mechanical response of teflon with respect to external loading used with these techniques. In this work, we assess other possibilities for artificial defects in CFRP matrix. For that a CFRP structure was developed and which incorporates teflon, flat-bottom holes and delamination obtained by the pull-out method. We experimentally studied the signals and we discuss the difference between the various artificial defects methods. [less ▲]

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See detailContrôle non destructif champ complet. Techniques et applications
Georges, Marc ULiege

Learning material (2017)

Ce cours a été donné lors de la journée de formation préliminaire au Colloque Francophone CMOI-FLUVISU de la Société Française d'Optique (SFO). Il s'adresse aux étudiants et chercheurs souhaitant une mise ... [more ▼]

Ce cours a été donné lors de la journée de formation préliminaire au Colloque Francophone CMOI-FLUVISU de la Société Française d'Optique (SFO). Il s'adresse aux étudiants et chercheurs souhaitant une mise à niveau avant d'assister au colloque. Le cours traite du controle non destructif par techniques optiques sans contact et champ complet, en vue de la mesure de déformation, la détection de défauts, la caractérisation non destructive des matériaux. [less ▲]

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