Bobbin pulsed eddy current array probe for detection and classification of defects in nonferromagnetic tubes

Abstract

The pulsed eddy current technique has received a great deal of attention in recent decades. To improve its performance and applicability, several kinds of probes, such as rectangular and gradient field probes for plate detection and encircling probes for tube detection, have been proposed. However, few bobbin-type pulsed eddy current probes have been proposed. This study proposes a bobbin pulsed eddy current array probe to simultaneously detect, classify and evaluate inner and outer surface defects in nonferromagnetic tubes. The probe contains double exciting coils and 20 sensors. The double exciting coils could generate stronger and more uniform induced eddy current in tube. The 20-sensors array could measure the complete circumferential magnetic signals above tube inner surface. Using the Br curves drawn by peak value and post peak value, inner and outer surface defects can be classified without beforehand training or the usage of complex process. Meanwhile, the maximum value in Br curve can be used to measure the defect depth and residual depth accurately.