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Personne :
Zhang, Hai

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Zhang

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Hai

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Université Laval. Laboratoire de vision et systèmes numériques

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ncf11735155

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Résultats de recherche

Voici les éléments 1 - 10 sur 15
  • PublicationAccès libre
    Thermographic non-destructive evaluation for natural fiber-reinforced composite laminates
    (Basel : MDPI, 2018-02-05) Avdelidis, Nicolas P.; Zhang, Hai; Sarasini, Fabrizio; Maldague, Xavier; Santulli, Carlo; Ibarra Castanedo, Clemente; Sfarra, Stefano; Fernandes, Henrique
    Natural fibers, including mineral and plant fibers, are increasingly used for polymer composite materials due to their low environmental impact. In this paper, thermographic non-destructive inspection techniques were used to evaluate and characterize basalt, jute/hemp and bagasse fibers composite panels. Different defects were analyzed in terms of impact damage, delaminations and resin abnormalities. Of particular interest, homogeneous particleboards of sugarcane bagasse, a new plant fiber material, were studied. Pulsed phase thermography and principal component thermography were used as the post-processing methods. In addition, ultrasonic C-scan and continuous wave terahertz imaging were also carried out on the mineral fiber laminates for comparative purposes. Finally, an analytical comparison of different methods was given.
  • PublicationAccès libre
    Non-destructive investigation of paintings on canvas by continuous wave terahertz imaging and flash thermography
    (Springer, 2017-04-05) Avdelidis, Nicolas P.; Fleuret, Julien; Saluja, Karan; Zhang, Hai; Peeters, Jeroen; Maldague, Xavier; Ibarra Castanedo, Clemente; Duan, Yuxia; Sfarra, Stefano; Fernandes, Henrique
    Terahertz (THz) imaging is increasingly used in the cultural heritage field. In particular, continuous wave (CW) and low frequency THz is attracting more attention. The first application of the THz technique inherent to the cultural heritage field dates back 10 years ago. Since 2006, tangible improvements have been conducted in the refinement of the technique, with the aim to produce clear maps useful for any art restorer. In this paper, a CW THz (0.1 THz) imaging system was used to inspect paintings on canvas both in reflection and in transmission modes. In particular, two paintings were analyzed: in the first one, similar materials and painting execution of the original artwork were used, while in the second one, the canvas layer is slightly different. Flash thermography was used herein together with the THz method in order to observe the differences in results for the textile support materials. A possible application of this method for the detection of artwork forgery requires some parameterization and analysis of various materials or thickness influence which will be addressed in a future study. In this work, advanced image processing techniques including principal component thermography (PCT) and partial least squares thermography (PLST) were used to process the infrared data. Finally, a comparison of CW THz and thermographic results was conducted.
  • PublicationAccès libre
    Enhanced infrared image processing for impacted carbon/glass fiber-reinforced composite evaluation
    (Molecular Diversity Preservation International (MDPI), 2017-12-26) Avdelidis, Nicolas P.; Zhang, Hai; Osman, Ahmad; Maldague, Xavier; Ibarra Castanedo, Clemente; Sfarra, Stefano; Fernandes, Henrique; Matikas, Theodore E.
    In this paper, an infrared pre-processing modality is presented. Different from a signal smoothing modality which only uses a polynomial fitting as the pre-processing method, the presented modality instead takes into account the low-order derivatives to pre-process the raw thermal data prior to applying the advanced post-processing techniques such as principal component thermography and pulsed phase thermography. Different cases were studied involving several defects in CFRPs and GFRPs for pulsed thermography and vibrothermography. Ultrasonic testing and signal-to-noise ratio analysis are used for the validation of the thermographic results. Finally, a verification that the presented modality can enhance the thermal image performance effectively is provided.
  • PublicationAccès 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, Xavier; 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.
  • PublicationAccès libre
    Thermographic non-destructive evaluation of carbon fiber-reinforced polymer plates after tensile testing
    (Plenum Press, 2015-09-17) Zhang, Hai; Maldague, Xavier; 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.
  • PublicationAccès libre
    An active infrared thermography method for fiber orientation assessment of fiber-reinforced composite materials
    (Pergamon, 2015-08-28) Zhang, Hai; Maldague, Xavier; 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.
  • PublicationAccès libre
    Fiber orientation assessment on randomly-oriented strands composites by means of infrared thermography
    (Elsevier Applied Science Publishers, 2015-11-02) Zhang, Hai; Maldague, Xavier; 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.
  • PublicationAccès 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, Xavier; 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.
  • PublicationAccès libre
    The axial crack testing model for long distance oil-gas pipeline based on magnetic flux leakage internal inspection method
    (Elsevier, 2017-02-28) Liu, Bin; Zhang, Hai; He, Lu-Yao; Fernandes, Henrique; Cao, Yang
    Traditional pipeline magnetic flux leakage (MFL) internal technology mainly uses axial excitation method, which could not recognize the narrow crack defects in the axial direction of the pipe. In this paper, by using a linear magnetic dipole model to study the circumferential excitation method, the detection model of axial crack in pipeline is established, and the relationship between MFL signals and the geometry characteristics of axial cracks is calculated. Finally, the detection accuracy and identification method of axial cracks is analyzed. Research results show that: non-uniform magnetic field generated by circumferential excitation can effectively detect the narrow cracks in the axial direction of the pipeline and distinguish the depth and the width characteristics of cracks. However, the background magnetic fields near the magnetic poles have great influence on the detection accuracy, and the smooth interpolation method of the cubic-spline interpolation can be used to reduce the influence effectively.
  • PublicationRestreint
    Study on characteristics of magnetic memory testing signal based on the stress concentration field
    (Institution of Engineering and Technology, 2017-01-01) Liu, Bin; Zhang, Hai; He, Yao Y.; Maldague, Xavier; Fernandes, Henrique; Fu, Ying
    Metal magnetic memory testing technology has been effectively used in stress concentration areas and micro-cracks detection of ferromagnetic metal components. However, due to the lack of profound theoretical basis and effective experimental research, the magnetic memory signal characteristics and magnetism quantitative relationship has not yet been determined. In this study, the full electronic potential magneto-mechanical model is established which is using the norm conserving pseudo-potential algorithm based on the first-principle. The quantitative relationship is then calculated between the stress concentration and the magnetic memory signal. The calculation results show that the changes of the wave function, which result from the stress concentration in the solid band, are the fundamental cause of the magnetic memory phenomenon, and atomic magnetic moment, lattice constant and the magnetic flux leakage signal strength linearly changes as a function of stress trend. As the stress concentration reached the critical stress point, the lattice structure was damaged, and the magnetic memory signal had undergone mutation. In this study, the experimental results are consistent with the theoretical calculation results.