Personne :
Zhang, Hai

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Université Laval. Laboratoire de vision et systèmes numériques
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Voici les éléments 1 - 8 sur 8
  • Publication
    Optimised 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, Gunther
    The 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.
  • Publication
    Accès libre
    An experimental and analytical study of micro-laser line thermography on micro-sized flaws in stitched carbon fiber reinforced polymer composites
    (Elsevier, 2016-04-01) Sheng, Yunlong; Yu, Ling Yao; Hassler, Ulf; Zhang, Hai; Maldague, X.; Robitaille, François; Genest, Marc; Joncas, Simon; Fernandes, Henrique; Holub, Wolfgang
    Stitching is used to reduce incomplete infusion of T-joint core (dry-core) and reinforce T-joint structure. However, it might cause new types of flaws, especially micro-sized flaws. In this paper, a new micro-laser line thermography (micro-LLT) is presented. X-ray micro-computed tomography (micro-CT) was used to validate the infrared results. The micro-LLT and micro-CT inspection are compared. Then, a finite element analysis (FEA) is performed. The geometrical model needed for finite element discretization was developed from micro-CT measurements. The model is validated for the experimental results. Finally a comparison of the experiments and simulation is conducted. The infrared experimental phenomenon and results are explained based on the FEA results
  • Publication
    Accès libre
    Comparative 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, Simon
    Stitching 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.
  • Publication
    Accès libre
    Experimental evaluation of pulsed thermography, lock-in thermography and vibrothermography on foreign object defect (FOD) in CFRP
    (Molecular Diversity Preservation International (MDPI), 2016-05-21) Liu, Bin; Zhang, Hai; Maldague, X.; Fernandes, Henrique
    In this article, optical excitation thermographic techniques, including pulsed thermography and lock-in thermography, were used to detect foreign object defect (FOD) and delamination in CFRP. Then, vibrothermography as an ultrasonic excitation technique was used to detect these defects for the comparative purposes. Different image processing methods, including cold image subtraction (CIS), principal component thermography (PCT), thermographic signal reconstruction (TSR) and Fourier transform (FT), were performed. Finally, a comparison of optical excitation thermography and vibrothermography was conducted, and a thermographic probability of detection was given.
  • Publication
    Accès libre
    Carbon 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, Gilmar
    Composite 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.
  • Publication
    Accès libre
    Fiber 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, Henrique
    In 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.
  • Publication
    Accès libre
    An active infrared thermography method for fiber orientation assessment of fiber-reinforced composite materials
    (Pergamon, 2015-08-28) Zhang, Hai; Maldague, X.; Fernandes, Henrique
    Fiber orientation in composite materials is an important feature since the arrangement or orientation of the fibers relative to one another has a significant influence on the strength and other properties of fiber reinforced composites. In this paper we present a method to assess the fiber orientation on the surface of carbon fiber reinforced polymer (CFRP) laminates. More specifically, a diode-laser beam is used to locally heat a small spot on the surface of the sample. Observation of the heat pattern in the infrared spectrum enables the assessment of the fiber orientation. Different samples and different regions on the surface of the samples are tested in order to estimate the precision of the method.
  • Publication
    Accès libre
    Thermographic 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, Henrique
    Infrared 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.