Personne : Zhang, Hai
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Université Laval. Laboratoire de vision et systèmes numériques
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- PublicationRestreintQualitative assessments via infrared vision of sub-surface defects present beneath decorative surface coatings(Springer, 2017-11-24) Lopez Rodriguez, Fernando; Zhang, Hai; Maldague, X.; Ibarra Castanedo, Clemente; Sfarra, Stefano; Fernandes, HenriqueIn this work, the potentialities of the infrared vision to explore sub-superficial defects in polychromatic statues were investigated. In particular, it was possible to understand how the reflector effect of the exterior golden layers could be minimized, applying advanced statistical algorithms to thermal images. Since this noble metal is present as external coating in both artworks, an in-depth discussion concerning its physicochemical properties is also added. In this context, the principal component thermography technique and, the more recent, partial least squares thermography technique were used on three different datasets recorded, providing long thermal stimuli. The main images were compared both to phasegrams and to the thermographic signal reconstruction results in order to have a clear outline of the situation to be debated. The effects of view factors on the radiation transfer linked to the specular reflections from the surface did not falsely highlight certain features inadvertently. Indeed, the raw thermograms were analyzed one by one. Reflectograms were used to pinpoint emissivity variations due to, e.g., possible repainting. The paper concludes that, as it is possible to understand from a physical point of view, the near-infrared reflectography technique is able to examine the state of conservation of the upper layers in cultural heritage objects, while the infrared thermography technique explores them more in-depth. The thesis statement is based on the thermal and nonthermal parts of the infrared region, therefore, indicating what can be detected by heating the surface and what can be visualized by illuminating the surface, bearing in mind the nature of the external coating.
- PublicationRestreintOptimised Dynamic line scan thermographic detection of CFRP inserts using FE updating and POD analysis(Elsevier, 2017-10-20) Peeters, Jeroen; Mokhtari, Mohammed-Yacine; Zhang, Hai; Maldague, X.; Ibarra Castanedo, Clemente; Khodayar, Fariba; Sfarra, Stefano; Dirckx, Joris; Steenackers, GuntherThe detection of delaminations in composite laminates using automated thermographic scanning is a quite challenging task. The set-up parameters are not only dependent on the equipment, but on the inspected component as well. In this work, a methodology is discussed to use Finite Element (FE) model updating to automatically establish the most suitable inspection parameters for a given combination of the structure and the investigated delamination depths. The optimised results are compared using binary Probability of Detection analysis and are benchmarked with parameter sets retrieved by an expert using the regular trial & error approach. The results show an improvement of the accuracy and scanning speed which significantly increases as the POD decreases and the complexity of the samples increases.
- PublicationAccès libreComparative study of microlaser excitation thermography and microultrasonic excitation thermography for submillimeter porosity in carbon fiber reinforced polymer composites(Society of Photo-optical Instrumentation Engineers, 2016-09-30) Zhang, Hai; Maldague, X.; Hassler, Ulf; Ibarra Castanedo, Clemente; Robitaille, François; Genest, Marc; Fernandes, Henrique; Joncas, SimonStitching is used to reduce incomplete infusion of T-joint core (dry-core) and reinforce T-joint structure. However, it may cause new types of flaws, especially submillimeter flaws. Thermographic approaches including microvibrothermography, microlaser line thermography, and microlaser spot thermography on the basis of pulsed and lock-in techniques were proposed. These techniques are used to detect the submillimeter porosities in a stitched T-joint carbon fiber reinforced polymer composite specimen. X-ray microcomputed tomography was used to validate the thermographic results. Finally an experimental comparison of microlaser excitation thermography and microultrasonic excitation thermography was conducted.
- PublicationAccès librePulsed micro-laser line thermography on submillimeter porosity in carbon fiber reinforced polymer composites : experimental and numerical analyses for the capability of detection(Optical Society of America, 2016-08-08) Fleuret, Julien; Zhang, Hai; Maldague, X.; Hassler, Ulf; Ibarra Castanedo, Clemente; Robitaille, François; Djupkep Dizeu, Frank Billy; Genest, Marc; Fernandes, Henrique; Joncas, SimonIn this article, pulsed micro-laser line thermography (pulsed micro-LLT) was used to detect the submillimeter porosities in a 3D preformed carbon fiber reinforced polymer composite specimen. X-ray microcomputed tomography was used to verify the thermographic results. Then, finite element analysis was performed on the corresponding models on the basis of the experimental results. The same infrared image processing techniques were used for the experimental and simulation results for comparative purposes. Finally, a comparison of experimental and simulation postprocessing results was conducted. In addition, an analysis of probability of detection was performed to evaluate the detection capability of pulsed micro-LLT on submillimeter porosity.
- PublicationAccès libreComparative study on submillimeter flaws in stitched T-joint carbon fiber reinforced polymer by infrared thermography, microcomputed tomography, ultrasonic c-scan and microscopic inspection(Society of Photo-optical Instrumentation Engineers., 2015-10-15) Zhang, Hai; Hassler, Ulf; Maldague, X.; Ibarra Castanedo, Clemente; Robitaille, François; Genest, Marc; Fernandes, Henrique; Joncas, SimonStitching is used to reduce dry-core (incomplete infusion of T-joint core) and reinforce T-joint structure. However, it may cause new types of flaws, especially submillimeter flaws. Microscopic inspection, ultrasonic c-scan, pulsed thermography, vibrothermography, and laser spot thermography are used to investigate the internal flaws in a stitched T-joint carbon fiber-reinforced polymer (CFRP) matrix composites. Then, a new microlaser line thermography is proposed. Microcomputed tomography (microCT) is used to validate the infrared results. A comparison between microlaser line thermography and microCT is performed. It was concluded that microlaser line thermography can detect the internal submillimeter defects. However, the depth and size of the defects can affect the detection results. The microporosities with a diameter of less than 54 μm are not detected in the microlaser line thermography results. Microlaser line thermography can detect the microporosity (a diameter of 0.162 mm) from a depth of 90 μm. However, it cannot detect the internal microporosity (a diameter of 0.216 mm) from a depth of 0.18 mm. The potential causes are given. Finally, a comparative study is conducted.
- PublicationAccès libreCarbon fiber composites inspection and defect characterization using active infrared thermography : numerical simulation and experimental results(Optical Society of America, 2016-09-23) Zhang, Hai; Maldague, X.; Figueiredo, Alisson; Ibarra Castanedo, Clemente; Fernandes, Henrique; Guimarares, GilmarComposite materials are widely used in the aeronautic industry. One of the reasons is because they have strength and stiffness comparable to metals, with the added advantage of significant weight reduction. Infrared thermography (IT) is a safe nondestructive testing technique that has a fast inspection rate. In active IT, an external heat source is used to stimulate the material being inspected in order to generate a thermal contrast between the feature of interest and the background. In this paper, carbon-fiber-reinforced polymers are inspected using IT. More specifically, carbon/PEEK (polyether ether ketone) laminates with square Kapton inserts of different sizes and at different depths are tested with three different IT techniques: pulsed thermography, vibrothermography, and line scan thermography. The finite element method is used to simulate the pulsed thermography experiment. Numerical results displayed a very good agreement with experimental results.
- PublicationAccès libreFiber orientation assessment on randomly-oriented strands composites by means of infrared thermography(Elsevier Applied Science Publishers, 2015-11-02) Zhang, Hai; Maldague, X.; Ibarra Castanedo, Clemente; Fernandes, HenriqueIn this paper, an infrared thermography technique is used to assess the fiber orientation on the surface of carbon fiber reinforced polymer (CFRP) moulded with randomly-oriented strands (ROS). Due to the randomness of the material, a point by point inspection would be very time consuming. In this paper it is proposed to use a flying laser spot technique to heat a line-region on the surface of the sample instead of a spot. During our experiments, a flying laser spot inspection was performed in 30 s while a point by point inspection of the same area would require about 25 min. An artificial neural network (ANN) was then used to estimate the fiber orientation over the heated line. The classification rate obtained with the network was 91.2% for the training stage and 71.6% for the testing stage.
- PublicationAccès libreThermographic non-destructive evaluation of carbon fiber-reinforced polymer plates after tensile testing(Plenum Press, 2015-09-17) Zhang, Hai; Maldague, X.; Ibarra Castanedo, Clemente; Fernandes, HenriqueInfrared thermography (IT) is a safe non-destructive evaluation technique that has a fast inspection rate and is generally contactless. It is used for diagnostics and monitoring in several fields including composite materials. In this paper carbon fiber-reinforced polymer plates submitted to tensile testing are inspected using IT. More specifically, carbon/polyether ether ketone panels made of random-oriented strands by compression moulding are submitted to tensile testing and then inspected using three different IT active approaches. The first two approaches use optical sources however with different scanning modes. The first active approach tested is a static surface scanning inspection in reflection mode. The second one is a dynamic line scanning technique where the energy source and camera are in movement with regards to the test sample. The last active IT approach tested uses a mechanical source (ultrasound excitation) to transfer heat to the sample being tested. This last approach is commonly called vibrothermography. Results obtained were then compared to results obtained by micro computed tomography inspection and microscopy. Results revealed voids associated with resin-rich regions as well as cracks.
- PublicationRestreintAutonomous high resolution inspection of kiss-bonds skins of carbon nanotube reinforced nanocomposites using novel dynamic line-scan thermography approach(Elsevier Applied Science Publishers, 2020-03-06) Zhang, Hai; Verberne, Pieter; Maldague, X.; Meguid, Shaker A.; Ibarra Castanedo, ClementeIn addition to being a serious threat to aircraft safety, kiss-bonding is also difficult to detect using conventional non-destructive testing techniques. It is the objective of this study to develop an autonomous high resolution technique to detect kiss-bonds and disbonds between carbon nanotube (CNT) skins and the host substrate of large-scale nanocomposite structures. The newly developed automated dynamic line-scan thermography (LST) approach is capable of speedy detection (up to 50 mm/s) of contact kiss-bonds as well as disbonds in laminated CNT-reinforced nanocomposite.
- PublicationRestreintImpact modelling and a posteriori non-destructive evaluation of homogeneous particleboards of sugarcane bagasse(Springer, 2018-01-12) Mokhtari, Mohammed-Yacine; Avdelidis, Nicolas P.; Sarasini, Fabrizio; Zhang, Hai; Fiorelli, Juliano; Maldague, X.; Peeters, Jeroen; Ibarra Castanedo, Clemente; Sfarra, Stefano; Lucca Sartori, Diogo de; Perilli, Stefano; Tirillò, JacopoWith a view to gaining an in-depth assessment of the response of particleboards (PBs) to different in-service loading conditions, samples of high-density homogeneous PBs of sugarcane bagasse and castor oil polyurethane resin were manufactured and subjected to low velocity impacts using an instrumented drop weight impact tower and four different energy levels, namely 5, 10, 20 and 30 J. The prediction of the damage modes was assessed using Comsol Multiphysics ®. In particular, the random distribution of the fibres and their lengths were reproduced through a robust model. The experimentally obtained dent depths due to the impactor were compared with the ones numerically simulated showing good agreement. The post-impact damage was evaluated by a simultaneous system of image acquisitions coming from two different sensors. In particular, thermograms were recorded during the heating up and cooling down phases, while the specklegrams were gathered one at room temperature (as reference) and the remaining during the cooling down phase. On one hand, the specklegrams were processed via a new software package named Ncorr v.1.2, which is an open-source subset-based 2D digital image correlation (DIC) package that combines modern DIC algorithms proposed in the literature with additional enhancements. On the other hand, the thermographic results linked to a square pulse were compared with those coming from the laser line thermography technique that heats a line-region on the surface of the sample instead of a spot. Surprisingly, both the vibrothermography and the line scanning thermography methods coupled with a robotized system show substantial advantages in the defect detection around the impacted zone.