Linearization of the lift-off effect for magnetic flux leakage based on Fourier transform

• Published in: Measurement science & technology 2021-06, Vol.32 (6), p.65012
• Main Authors: Wang, Jie, Li, Erlong, Wu, Jianbo, Xu, Xianyou
• Format: Article
• Language: English
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/1361-6501/abe89e

In magnetic flux leakage testing, the lift-off effect shows that testing signal voltages vary with lift-off values. This has many adverse effects on detection and evaluation. This paper proposes a novel method for linearization of the lift-off effect in the spatial domain. The spatial analytical expression is obtained through magnetic dipole theory and the Fourier transform method. An analytical method to linearizethe lift-off effect is proposed. Further, the finite-element method and discrete Fourier transform method are applied to linearize the lift-off effect. Experimental studies are also conducted to verify the analytical results. The linear fitting function of the lift-off effect takes the form of Y = AX + B . When the spatial frequency ω is 35 mm −1 , the linear fitting results of the simulation and experiment are Y = −0.23596 X −2.0268 and Y = −0.23511 X + 4.8152. The goodness of fit R 2 is 0.9997 and 0.9975. The results show that the lift-off effect can be linearized in the spatial domain. The coefficient A is slightly affected by the defect size. The coefficient B is strongly related to the defect size. We consider these results to be quite significant.