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.
[1]
Clemente Ibarra-Castanedo,et al.
Defect depth retrieval from pulsed phase thermographic data on Plexiglas and aluminum samples
,
2004,
SPIE Defense + Commercial Sensing.
[2]
Clemente Ibarra-Castanedo,et al.
Pulsed phase thermography inversion procedure using normalized parameters to account for defect size variations
,
2005,
SPIE Defense + Commercial Sensing.
[3]
S. Marinetti,et al.
Pulse phase infrared thermography
,
1996
.
[4]
Sergio Marinetti,et al.
Pulse phase thermography for defect detection and visualization
,
1999,
Smart Structures.
[5]
Xavier Maldague,et al.
Time aliasing problem in pulsed-phased thermography
,
2001,
SPIE Defense + Commercial Sensing.
[6]
C. Ibarra-Castanedo,et al.
Discrete signal transforms as a tool for processing and analyzing pulsed thermographic data
,
2006,
SPIE Defense + Commercial Sensing.
[7]
Gerhard Busse,et al.
Phase-sensitive modulation thermography and its applications for NDE
,
1997,
Defense, Security, and Sensing.