Characterization of image sequences of a defect using pulsed eddy current signals

Abstract Pulsed eddy current testing (PECT) has the advantages of rich information, efficiency and noncontact among defect nondestructive testing. Pulsed eddy current imaging technology also has a wide range of applications. However, the imaging method based on single feature is mostly adopted at this stage. In order to make better use of pulsed eddy current signals, signal slice based method was proposed for pulsed eddy current sequence imaging. Through the difference analysis of air-subtracted signal (ASS) and non-defect-subtracted signal (NDSS), sequence imaging in different ways is carried out. The influence of defects was explained by visualizing the diffusion of eddy currents in different specimens using a finite element model. ASS and NDSS image sequences were evaluated through image quality evaluation and quantitative identification. The result shows that there are some image frames in the image sequence that are better than the images generated by a single feature value in the image quality evaluation and quantitative analysis. It proves that the image sequence contains more defect information, which also illustrates the information richness of pulse eddy current detection.