Demagnetization Scheme for Avoiding Magnetic Mines Under the Exposure of Earth Magnetic Field

Demagnetization of warship is needed to reduce residual magnetization to avoid the detection of magnetic mines. However, after demagnetized, it could be magnetized again by the earth magnetic field during the operation. In order to accomplish a robust deperming protocol to avoid the influence of earth magnetic field after demagnetization, this paper proposes a demagnetization protocol which utilize the interaction field inside the material to maintain magnetization state of a small coercive particles. By using the Preisach modeling combined with finite-element method, it was confirmed that the proposed protocol reduces the effect of the earth magnetic field and it was verified by the experimental measurements. Coincident results in different coercive materials showed an effectiveness of this protocol.