3D analysis of inspection method of opposite side defect in steel using AC square wave magnetic field with DC bias taking account of minor loop

The alternating magnetic flux leakage testing is one of the electromagnetic non-destructive inspection method for detecting the surface defect on steel plate. By this inspection method, since the alternating magnetic field of high frequency is used, only the surface defect on the steel plate is detected. In this paper, the inspection method for the opposite side defect in the steel plate using the magnetizing current of AC square wave on DC bias by this inspection technique is proposed. The behavior of flux in steel is examined using 3-D nonlinear FEM taking account of minor loops and eddy current. It is shown that the inspection of opposite side defect in the steel plate is possible by using the impressed magnetic field AC square wave on DC bias.