Enhanced image processing for infrared non-destructive testing

López, Fernando; Maldague, Xavier; Ibarra-Castanedo, Clemente

doi:10.2478/s11772-014-0202-2

Cited by 21 publications

(8 citation statements)

References 8 publications

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“…Phase Fourier Analysis (PFA) (e.g. Pulsed Phase Thermography) is widely used to produce phase images from thermal data [31]. In PFA, each thermal signal is transformed from the time domain to the frequency one using the well-known discrete Fourier transform (DFT) [37]:…”

Section: Phase Fourier Analysis (Pfa)mentioning

confidence: 99%

“…Advanced post-processing techniques are reported for optical IR thermography such as Absolute Thermal Contrast (ATC), Thermographic Signal Reconstruction (TSR), Phase Fourier Analysis (PFA) and Principal Component Analysis (PCA) [26][27][28][29][30]. These data processing methods have shown to provide enhanced detection and quantification of material damage in the presence of thermal image artefacts caused by non-uniform heating of the test surface, anisotropic diffusivities and additive noise such as environmental reflections and emissivity variations [31]. This paper presents a quantitative experimental analysis of LPT for the assessment of material damage in both CFRP and GFRP composite laminates.…”

Section: Introductionmentioning

confidence: 99%

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Image processing based quantitative damage evaluation in composites with long pulse thermography

Wang

Tian

Meo

et al. 2018

NDT & E International

112

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Pulsed thermography is a contactless and rapid non-destructive evaluation (NDE) technique that is widely used for the inspection of fibre reinforced plastic composites. However, pulsed thermography uses expensive and specialist equipment such high-energy flash lamps to generate heat into the sample, so that alternative thermal stimulation sources are needed. Long pulse thermography was recently developed as a cost-effective solution to enhance the defect detectability in composites by generating step-pulse heat into the test sample with inexpensive quartz halogen lamps and measuring the thermal response during the material cooling down. This paper provides a quantitative comparison of long pulse thermography with traditional pulsed thermography and step heating thermography in carbon fibre and glass fibre composites with flat-bottomed holes located at various depths. The three thermographic methods are processed with advanced thermal image algorithms such as absolute thermal contrast, thermographic signal reconstruction, phase Fourier analysis and principal component analysis in order to reduce thermal image artefacts. Experimental tests have shown that principal component analysis applied to long pulse thermography provides accurate imaging results over traditional pulsed thermography and step heating thermography. Hence, this inspection technique can be considered as an efficient and cost-effective thermographic method for low thermal conductivity and low thermal response rate materials.

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Section: Phase Fourier Analysis (Pfa)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Image processing based quantitative damage evaluation in composites with long pulse thermography

Wang

Tian

Meo

et al. 2018

NDT & E International

112

View full text Add to dashboard Cite

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“…These data processing methods reduce thermal image artefacts, which are caused by non-uniform heating or thermal reflections from the environment. In this way, the detectability of defects is increased and a quantification is possible [26]. Sanati et al, for example, performed a comparison of pulse and step-heating thermography on a coated GFRP sample.…”

Section: Introductionmentioning

confidence: 99%

Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure

et al. 2021

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Initial defects, for example, those occurring during the production of a rotor blade, encourage early damages such as rain erosion at the leading edge of wind turbine rotor blades. To investigate the potential that initial defects have for early damage, long-pulse thermography as a non-destructive and contactless measurement technique is applied to a strongly curved and coated test specimen for the first time. This specimen is similar in structural size and design to a rotor blade leading edge and introduced with sub-surface defects whose diameters range between 2mm and 3.5mm at depths between 1.5mm and 2.5mm below the surface. On the curved and coated test specimen, sub-surface defects with a depth-to-diameter ratio of up to 1.04 are successfully detected. In particular, defects are also detectable when being observed from a non-perpendicular viewing angle, where the intensity of the defects decreases with increasing viewing angle due to the strong surface curvature. In conclusion, long-pulse thermography is suitable for the detection of sub-surface defects on coated and curved components and is therefore a promising technique for the on-site application during inspection of rotor blade leading edges.

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“…Infrared imagers can transform the thermal energy into a visible image [4]. Optical pulsed thermography has the advantages of speed and ease, and especially its capability to be employed on different types of materials [5]. However, this method cannot provide a very good signalto-noise ratio (SNR) [6].…”

Section: Introductionmentioning

confidence: 99%

Automatic internal crack detection from a sequence of infrared images with a triple-threshold Canny edge detector

Wang

Tse

Yuan

2018

Meas. Sci. Technol.

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Visual inspection and assessment of the condition of metal structures are essential for safety. Pulse thermography produces visible infrared images, which have been widely applied to detect and characterize defects in structures and materials. When active thermography, a non-destructive testing tool, is applied, the necessity of considerable manual checking can be avoided. However, detecting an internal crack with active thermography remains difficult, since it is usually invisible in the collected sequence of infrared images, which makes the automatic detection of internal cracks even harder. In addition, the detection of an internal crack can be hindered by a complicated inspection environment. With the purpose of putting forward a robust and automatic visual inspection method, a computer vision-based thresholding method is proposed. In this paper, the image signals are a sequence of infrared images collected from the experimental setup with a thermal camera and two flash lamps as stimulus. The contrast of pixels in each frame is enhanced by the Canny operator and then reconstructed by a triple-threshold system. Two features, mean value in the time domain and maximal amplitude in the frequency domain, are extracted from the reconstructed signal to help distinguish the crack pixels from others. Finally, a binary image indicating the location of the internal crack is generated by a K-means clustering method. The proposed procedure has been applied to an iron pipe, which contains two internal cracks and surface abrasion. Some improvements have been made for the computer vision-based automatic crack detection methods. In the future, the proposed method can be applied to realize the automatic detection of internal cracks from many infrared images for the industry.

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Enhanced image processing for infrared non-destructive testing

Cited by 21 publications

References 8 publications

Image processing based quantitative damage evaluation in composites with long pulse thermography

Image processing based quantitative damage evaluation in composites with long pulse thermography

Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure

Automatic internal crack detection from a sequence of infrared images with a triple-threshold Canny edge detector

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