Time and frequency behaviour in TSR and PPT evaluation for flash thermography
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In: Quantitative infra red thermography (QIRT Journal), Vol. 14.2017, No. 2, 2017, p. 164-184.
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TY - JOUR
T1 - Time and frequency behaviour in TSR and PPT evaluation for flash thermography
AU - Oswald-Tranta, Beata
PY - 2017
Y1 - 2017
N2 - Subsurface defects can be detected by flash thermography evaluating the temperature response at the surface. Many techniques have been developed in the past to localise defects and also to estimate their depth and size. Two of the most established methods are TSR and PPT, whereby TSR analyses the data in the time domain, and PPT evaluates the signal in the frequency domain. In order to get the data in the frequency domain, Fourier transformation, especially FFT is used to calculate the phase shift for the different frequencies. The usage of FFT assumes a periodic signal or a temporal signal limited in time. As this is not the case for the temperature signal after a short pulse heating, the transformation to the frequency domain generates some errors. Therefore parameters as e.g. sampling frequency or time duration of evaluation have to be selected carefully. Even if many publications have been already dealing with this topic, in this paper a new approach is attempted by comparing the temporal behaviour as it is handled by the TSR technique with the frequency behaviour calculated by PPT. The results are interpreted with the help of simulation and measurements for flat bottom hole samples are also presented.
AB - Subsurface defects can be detected by flash thermography evaluating the temperature response at the surface. Many techniques have been developed in the past to localise defects and also to estimate their depth and size. Two of the most established methods are TSR and PPT, whereby TSR analyses the data in the time domain, and PPT evaluates the signal in the frequency domain. In order to get the data in the frequency domain, Fourier transformation, especially FFT is used to calculate the phase shift for the different frequencies. The usage of FFT assumes a periodic signal or a temporal signal limited in time. As this is not the case for the temperature signal after a short pulse heating, the transformation to the frequency domain generates some errors. Therefore parameters as e.g. sampling frequency or time duration of evaluation have to be selected carefully. Even if many publications have been already dealing with this topic, in this paper a new approach is attempted by comparing the temporal behaviour as it is handled by the TSR technique with the frequency behaviour calculated by PPT. The results are interpreted with the help of simulation and measurements for flat bottom hole samples are also presented.
KW - defect detection
KW - Flash thermography
KW - PPT
KW - thermal wave
KW - TSR
UR - http://www.scopus.com/inward/record.url?scp=85011255382&partnerID=8YFLogxK
U2 - 10.1080/17686733.2017.1283743
DO - 10.1080/17686733.2017.1283743
M3 - Article
AN - SCOPUS:85011255382
VL - 14.2017
SP - 164
EP - 184
JO - Quantitative infra red thermography (QIRT Journal)
JF - Quantitative infra red thermography (QIRT Journal)
SN - 1768-6733
IS - 2
T2 - Thermosense: Thermal Infrared Applications XXXIX 2017
Y2 - 10 April 2017 through 13 April 2017
ER -