Multidirectional Scanning-Based Eddy Current Testing for Cavity and Crack Discrimination

Motivated by the significant disparity in the aspect ratio of cavity and crack defects, this paper proposes a multi-directional scanning-based eddy current (EC) testing strategy for distinguishing between these two types by analyzing the characteristics of the perturbed EC and the corresponding magnetic flux density fields. To enable efficient simulation and verification of the strategy, the distributed current source method is enhanced by incorporating solution domain rotation, allowing accurate modeling of defects at arbitrary orientations. A symmetrical relationship among scanning images is also discussed to reduce the number of required simulations. The validity of the improved numerical model is demonstrated through comparing with finite element analysis results. Simulated scanning images for various defect orientations are then used to identify a key parameter that enables reliable classification. Finally, the proposed strategy is experimentally validated using a testbed mounted on a servo-positioning platform, confirming its effectiveness even when applied to workpiece materials different from those used in the simulations.