4 August 2009 Pulsed phase thermography for defect detection of honeycomb structure
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Pulse Phase Thermography (PPT) has been reported as a powerful technique of the thermal NDE. In this paper, the authors show that the original phase-images of two kinds of honeycomb structure defects by PPT based on Fast Fourier Transform (FFT) for the signal of temperature-time of each pixel. One is the artificial defects in honeycomb structure core under surface skin, and the defects can be identified easily. The other is disbonding defect between surface skin and core, and the difference is apparent compared with bonding and no-bonding between surface skin and core. To improve the signal to noise ratio for defect inspection of honeycomb structure, the temperature decay curve of each pixel is smoothed by moving average filter and then fitted by exponential function. After FFT on the fitted data of temperature, the fitted phase-images of two kinds of honeycomb structure defects are given. Compared with the original thermal-images of PT and original phase-images, the calculated phase-images are much more improved. Another advantage is the data could be represented by coefficients of fitting functions, and the storage of data could be greatly reduced. At last, the calculation process of temperature decay curve and analysis of the influence caused by increasing sampling time and frequency are given.
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Yan Zhang, Yan Zhang, Lichun Feng, Lichun Feng, Yanhong Li, Yanhong Li, Cunlin Zhang, Cunlin Zhang, } "Pulsed phase thermography for defect detection of honeycomb structure", Proc. SPIE 7383, International Symposium on Photoelectronic Detection and Imaging 2009: Advances in Infrared Imaging and Applications, 73830G (4 August 2009); doi: 10.1117/12.835962; https://doi.org/10.1117/12.835962

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