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 -