Proposal of electromagnetic inspection of opposite side defect in steel using 3-D nonlinear FEM taking account of minor loop and residual magnetization

The inspection of the opposite side defect in the steel wall in the petrochemical plant is necessary for safe maintenance. Generally, the alternating magnetic flux leakage testing (AMT) is used for detecting only the surface defect of the steel plate. In this paper, electromagnetic inspection method for the detecting of the opposite side defect in steel plate using this AMT method by applying the residual magnetization is investigated. The synthetic magnetic field of both residual magnetization and alternating magnetic field is estimated by 3D nonlinear FEM taking account of the hysteresis and minor loop characteristics of the steel plate.