Magnetic-Charge Element Method for Magnetic Flux Leakage Inspection

Magnetic flux leakage (MFL) inspection is widely used in testing and evaluating of defects in ferromagnetic structures, providing important assurances for their safe operations. The calculation of MFL signals based on defects shape is critical for the accuracy of defect evaluation. The existing methods mainly include magnetic dipole model (MDM) and finite element method (FEM), while MDM is incapable of calculating the MFL fields of complex defects, and FEM is time-consuming for the MFL analysis. It is necessary to develop a method which can calculate MFL fields of arbitrary defects fast. In this paper, we propose the magnetic charge element method (MCEM) based on the microscopic mechanism of magnetization and the theory of MDM, which can quickly calculate the MFL fields of arbitrary defects. The effectiveness of the proposed method is verified by a series of simulations and MFL inspection experiments. The results show that the proposed method has the same accuracy as the existing methods. Compared with the FEM, the computation time is greatly reduced.