A Novel Pipeline Defect Detection Method Using an Arc-Shaped Eddy Current Probe

Eddy current testing (ECT), as a noncontact and nondestructive testing (NDT) technology, has been widely applied to various industrial fields for pipeline defect detection. In this article, a combined defect parameter estimation method using a novel arc-shaped differential probe with orthogonal receivers is proposed to detect circumferential defects in pipelines. The sensitivity between coils is analyzed to optimize the probe parameters. The scanning signals of defects on the complex plane are characterized by the shell curves (SCs), and a Lissajous curve (LC) model is employed for curve fitting. It is observed that a monotonous relationship holds between fitting parameters and defect dimensions. From the fit scanning curve, the defect depth and length can be estimated by employing the K-nearest neighbors (KNNs) algorithm. Experiments have been conducted to verify the proposed defect parameter estimation method by testing aluminum pipelines with cracks. The experimental results show that the estimation of defect parameters achieves an average accuracy (ACC) of more than 96.78% for various dimensions of cracks.