Analytical Method for Pulsed Eddy Current Field of Flat-Bottomed Hole Defect Based on Defect Equivalent Source Model

Pulsed eddy current testing (PECT) is an electromagnetic nondestructive inspection technology capable of detecting pipe corrosion in-service without the need to remove the insulation coating. However, current PECT inspection methods based on intact conductor models lack sufficient accuracy in quantitative evaluation of localized corrosion defects, restricting their wider application. Based on the analytical model of the intact metal plate, this paper develops a defect equivalent source model to analytically solve the eddy current field of conductors containing flat-bottomed hole defects, thereby improving computational accuracy and efficiency. First, artificial current excitation sources are introduced in the defect region to establish a defect equivalent source model, and the boundary-value problem for this model is solved. Then an iterative algorithm is employed to determine the defect equivalent source magnitudes based on the condition that the total current density within the defect region is zero. Subsequently, the time-domain analytical solution for the induced voltage in the PECT of the metal plate with defects is derived using the superposition principle. Finally, experiments on an aluminum alloy plate containing cylindrical flat-bottom hole defects validate the accuracy of the proposed defect equivalent source model and demonstrate its feasibility and advantages in analytically solving the eddy current field involving defects. The findings significantly enrich the analytical methods for defect-containing eddy current field and lay a theoretical foundation for innovation in PECT technology for localized corrosion defects.