Defect characterisation based on pulsed eddy current imaging technique

The pulsed eddy current (PEC) technique is an emerging electromagnetic method, which is widely applied to detect defects in the field of nondestructive testing and evaluation (NDT&E). This paper studied the PEC imaging technique to identify and evaluate the corrosion type of defects. Based on PEC probe consisting of a rectangular exciting coil and an induction pick-up coil, the C-scan imaging technique is researched and analyzed in two directions (magnetic induction flux and exciting current). The averaging method and wavelet transform are used to de-noise the response PEC signals. Experiment results have shown that the corrosion type of defect can be identified effectively by particular character based on rectangular exciting coil in both directions, and that the results in direction of magnetic induction flux are more effective than those in direction of exciting current. Defect characterisation is carried out based on the C-scan image. The defects are discriminated to surface defect by selecting the rising time as the feature and the sizing of defects are preliminarily obtained based on the imaging results. To sum up, the PEC imaging technique is an effective means to evaluate the corrosion type of defects, which can be extended to the characterisation of complex defects.