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Particular ship sailing their environment , external force is serious , complex internal structure , hull steel plate can easily form various defects , the security threat to the normal operation of the ship . Steel plate defects will seriously affect the operation of the ship 's stability, and reliable. In order to ensure the safety of the ship , you must make regular checks of ship plate , in order to repair or replace the defective component . This paper presents a theoretical model of the magnetic flux leakage calculations, finite element simulation and test three methods of steel plate defect leakage magnetic field analysis . Mechanism of magnetic flux leakage , the magnetic dipole model analysis method for different forms of defects , analyzed and the impact of the law on crack parameters ( crack depth , width , lift-off , etc.) , and analysis of the leakage magnetic field strength and other relevant factors . Through comparative analysis of different magnetization and the object of this paper , the use of local magnetization of the permanent magnet , and optional rubidium iron boron permanent magnet materials , design the the magnetized structure of the initial model , study and magnetization operating point . ANSYS to establish the finite element model , optimize the design of the excitation device , including the permanent magnet thickness , width , magnetization gap , etc. , to design the most reasonable magnetized device ; View the magnetic field lines distribution by ANSYS simulation results , the leakage magnetic field size distribution situation defects near the magnetic flux leakage signal for the detection of magnetic flux leakage signal basis . Signal acquisition, according to the characteristics of steel sheet detection by comparing the selection of the magnetic flux leakage coil sensors array using electromagnetic detector detect the experimental steel , and the detection results of the analyzes : the detection signal occurs when positive and negative transitions , the the sensor array is the location of the defect location . According to the amplitude of the signal transition can judge the depth of defect roughly range hopping signal covers the range of the number of channels can understand , the width of the information of the defect . In this paper, the analysis of the leakage magnetic field is developed to provide a basis for leakage magnetic detection equipment .
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