Defect edge identification with rectangular pulsed eddy current sensor based on transient response signals

The Pulsed Eddy Current (PEC) testing is an increasingly emerging nondestructive testing & evaluation (NDT&E) technique. The main purpose of this study is to improve the performance of defect edge identification of C-scan imaging technique utilizing the rectangular PEC sensor. When sensor scans along the defect, peak waves of response signals always present a crest and a trough in direction of magnetic induction flux, while present different shapes in direction of exciting current. The maximum and minimum values of peak waves in direction of magnetic induction flux are corresponding to the moment of sensor entering and leaving the length edge of defect, which provides us a way to evaluate the length edge of defect. To evaluate the width edge of defect, we obtain and analyze the C-scan imaging results in direction of magnetic induction flux. For improving the identification of width edge of defect, we proposed news features from response signals and differential response signals. Experiment results have shown that the width edge of defects on surface can be identified effectively by selecting and normalizing the appropriate features in time domain. Therefore, both length edge and width edge of defect can be evaluated effectively in direction of magnetic induction flux. The rectangular PEC sensor is helpful for C-scan imaging inspection technique and has a good prospect in field of nondestructive testing & evaluation. Crown Copyright & 2010 Published by Elsevier Ltd. All rights reserved.