An Improved MFL Method Fusing Multi-Space Magnetic Field Information for The Surface Defect Inspecting.

Nondestructive testing (NDT) for the ferromagnetic materials is significant to guarantee the safety of the industrial facilities. However, traditional NDT methods all have some limitations in detecting and evaluating the surface omnidirectional defects, especially those shallow flaws. This paper first proposes an improved MFL method utilizing the multi-space magnetic field (MSMF) information to detect the surface defect in the steel slab. By analyzing the characteristics of spatial magnetic field, another zone rich in defect information, besides the middle zone, is found. Then the fusion detection algorithm is proposed combining the horizontal component of the magnetic field in the middle zone and the normal component in the newly chosen position. The simulation testing and experimental results all indicate that the proposed method has good performance in identifying the surface defects in various direction.