Characterization of Crack Geometry Parameters Based on Three-dimensional Transient Magnetic Field of Rectangular Pulsed Eddy Current

Eddy current testing plays an important role in assessing the surface quality of metal structures. Based on pulsed eddy current (PEC) testing, a new magnetic field characterization technique for surface cracks is proposed in this paper. The three-dimensional transient magnetic field is studied, revealing its distribution characteristics and transient response in the presence of cracks. The results show that the transient magnetic field contains valuable information. Specifically, the distributions of the magnetic field components Bx and Bz at the initial time are effective in evaluating crack length and depth. The time response of Bx provides characteristic information about defect length, emphasizing the importance of selecting the appropriate detection location. Additionally, the peak position and response amplitude of Bz can characterize crack depth. The effects of the pulse rising time and coil liftoff on the transient magnetic field are also studied. The study shows that the pulse rising time should be as short as possible, and the characteristics of rectangular PEC help mitigate the effects of liftoff. The rich features extracted from the transient magnetic field provide a new means to evaluate crack geometry, improving testing capabilities and detection accuracy.