Non-destructive evaluation of thick glass fiber-reinforced composites by means of optically excited lock-in thermography

Montanini, Roberto; Freni, F.

doi:10.1016/j.compositesa.2012.06.004

Cited by 71 publications

(27 citation statements)

References 22 publications

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“…The phase and amplitude information calculated by processing of recorded thermal images for each of the pixels are stored in the form of 2D matrices and subsequently converted to images known as phase image and amplitude image. [26][27][28][29] The amplitude image displays total temperature increase on the system during power cycling and phase image represents the time delay between powering a device and subsequent heating on the surface. Amplitude images are quantitatively analyzed to acquire the defect shape & size and phase image for defect's depth.…”

Section: Introductionmentioning

confidence: 99%

Investigation of lock-in infrared thermography for evaluation of subsurface defects size and depth

Shrestha

Kang

Kim

2015

Int. J. Precis. Eng. Manuf.

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In this study, the investigation on lock-in infrared thermography was done for the detection and estimation of artificial subsurface defects size and depth in stainless steel sample. The experimental and the finite element analysis were performed at several excitation frequencies to interrogate the sample ranging from 0.182 down to 0.021 Hz. A finite element model using 'ANSYS 14.0' was used to completely simulate the lock-in thermography. The four point method was used in post processing of every pixel of thermal images using the MATLAB programming language. A signal to noise ratio analysis was performed on both phase and amplitude images in each excitation frequency to determine the optimum frequency. The relationship of the phase value with respect to excitation frequency and defect depths was examined. Amplitude image was quantitatively analyzed using Vision Assistant, a special tool in LABVIEW program to acquire the defects size. The phase image was used to calculate the defects depth considering the thermal diffusivity of the material and the excitation frequency for which the defects become visible. A finite element analysis result was found to have good correlation with experimental result and thus demonstrated potentiality in quantification of subsurface defects.

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Section: Introductionmentioning

confidence: 99%

Investigation of lock-in infrared thermography for evaluation of subsurface defects size and depth

Shrestha

Kang

Kim

2015

Int. J. Precis. Eng. Manuf.

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“…Thus, similar effects must be expected when other methods than FFT are exploited to evaluate phase differences in temperature transients of LT. This is of particular interest, if obtained values of phase differences are needed for the determination of material properties [7] or the depth of a defect [11].…”

Section: Simulated Temperature Transientsmentioning

confidence: 99%

“…However, most of publications dealing with LT contain no statements at all as to whether and how the DC components were corrected e.g. [10][11][12][13]. This is particularly critical when calibrations are related to phase angles [14] or the absolute value of a phase difference is required for further calculations [11].…”

Section: Introductionmentioning

confidence: 99%

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Systematic errors in the evaluation of uncorrected data from thermographic lock-in measurements

Krankenhagen¹,

Ziegler²,

Maierhofer³

2018

Proceedings of the 2018 International Conference on Quantitative InfraRed Thermography

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Lock-in thermography (LT) is based on the correct evaluation of phase differences between the temperature oscillations at different surface regions of the object under test during periodic heating. Since the usual heating procedures contain a DC component, the actual heating pattern achieved is not harmonic. This causes systematic deviations when phase differences are determined by means of harmonic analysis, e.g. with FFT analysis. The resulting errors depend clearly on the ratio between DC and AC amplitude, which is demonstrated at simulated and experimentally recorded temperature transients. Further experimental LT data obtained by different oscillating energy inputs showed a variety of possible shapes of transients with different DC components..

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“…Active IR thermography is a powerful non-destructive technique that has been extensively used for detecting defects in materials [18,19]. However, it has never been applied to identify deteriorated alphanumeric marks.…”

Section: Introductionmentioning

confidence: 99%

Restoration of abraded and covered marks engraved in steel using active infrared thermography

Quattrocchi¹,

Piccolo²,

Montanini³

2016

Proceedings of the 2016 International Conference on Quantitative InfraRed Thermography

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Alphanumeric marking is a common technique employed in industrial applications for identification of products. However, the realised mark can undergo deterioration, either by extensive use or voluntary deletion (e.g. removal of identification numbers of weapons or vehicles). For recovery of the lost data many destructive or non-destructive techniques have been endeavoured so far, which however present several restrictions. In this paper, active infrared thermography has been exploited for the first time in order to assess its effectiveness in restoring paint covered and abraded labels made by means of different manufacturing processes (laser, dot peen, impact, press and scribe). Optical excitation of the target surface has been achieved using pulse, lock-in and step heating. Raw infrared images were analysed with a dedicated image processing software originally developed in Matlab, exploiting several methods, which include thermographic signal reconstruction, guided filtering and logarithmic transformation.

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Non-destructive evaluation of thick glass fiber-reinforced composites by means of optically excited lock-in thermography

Cited by 71 publications

References 22 publications

Investigation of lock-in infrared thermography for evaluation of subsurface defects size and depth

Investigation of lock-in infrared thermography for evaluation of subsurface defects size and depth

Systematic errors in the evaluation of uncorrected data from thermographic lock-in measurements

Restoration of abraded and covered marks engraved in steel using active infrared thermography

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