Magnetic flux leakage (MFL) testing is commonly used as an inspection technique in ferromagnetic metal material. In this paper, measurement of the three-dimensional (3D) pulsed magnetic leakage flux field (PMFL) is proposed to overcome the shortcomings of traditional MFL measurement, which only uses the x-axis component of the magnetic field. The finite element method (FEM) has been used to simulate and analyse the characteristics of a surface axial and circumferential defect magnetic field in three independent x-, y- and z-axes. The experimental and FEM results show that data from x-, y- and z-axis components can give comprehensive positional information about defects, particularly their shape and orientation, especially when the defect is parallel to the applied field. The experimental results show good correlation with the simulation. The work concludes that 3D pulsed magnetic leakage field sensing could be used to improve the defect characterisation capabilities, and FEM can help to improve the design of the PMFL systems.
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Tang et al. (2011) studied this question.