analysis of flash pulse thermographic inspection parameters for quantitative measurement

Abstract

Flash-pulse thermography is a method for the detection of discontinuities or inhomogeneities in materials at their surface. It is based on excitation of inspected samples by a short pulse and analysis of its thermal response. It is basically an indicative method, however, quantitative procedures for an evaluation of defects detectability, defects depths or a thickness of coatings are also developed. The quantitative evaluation has, in general, higher demands on the accuracy of a measurement procedure. This contribution is focused on the analysis of parameters of recording of thermographic data. The influence of synchronization of a sample thermal response recording with an excitation source is analyzed. Differences between recording using a bolometric thermographic camera and a cooled detector based thermographic camera are demonstrated on flat-bottom hole samples. The results show that a high-level synchronization is crucial for the quantitative evaluation of flash-pulse thermography. It is also shown that the cooled quantum detector based thermographic cameras have better temperature response in the case of cooling process measurement and can produce higher sensitivity and lower noise records. Thus, it should be used for any quantitative flash-pulse thermography measurement, even if a bolometric detector type camera would satisfied framerates requirements.