Detecting of defects in heat-resistant alloy coating structure plates using pulsed infrared thermography

Aiming at developing a method for defects detection in heat-resistant alloy coating structure by pulsed infrared thermography, test was applied to heat-resistant alloy coating structure plates with blind-bottom holes, combining finite element simulation and experimental study. In order to provide a theoretical basis for the determination of sampling frequency and time in tests, finite element method was adopted to analyze the transfer process of heat pulse excited to the specimen. Flash lamps were used as active heat source into the sample, and the thermal-wave image sequences were collected with FLIR SC7000 infrared camera. Fitting-correlation algorithm(FCA), pulsed phase thermography(PPT) and principal component analysis(PCA) method were used to process the image sequences. Experimental results show that the SNR of processed images by PPT and PCA increases significantly under given test parameters, and can be used to detect the defects in heat-resistant alloy coating structure plates.