Further development of MFL requires efforts to minimize influence of various factors on the MFL signal. Estimation of their dimensions is a non-trivial issue while considering number of factors that influence the magnitude of an MFL signal. Some of these anomalies are indicators of macroscopic defects, such as corrosion pits, dents, cracks etc. Modern MFL tools are suitable for fast detection and classification of magnetic anomalies. Magnetic flux leakage (MFL) is commonly used as a qualitative inspection method. It was stated that eddy currents generated below the poles lead to a change of plate magnetization as well as to a change of magnetic field distribution above the top surface of the plate, what is observed as a shift of the MFL signal baselines. The finite element method was used to study the distribution of velocity-induced eddy currents in the investigated plate. An empirical compensation scheme was formulated, and it was used to minimize distortions of the normal component caused by the velocity effect. It was shown that the baseline value of the normal component is proportional to the velocity. The normal component was found to be the most sensitive to the velocity effect. In addition to them, the gradient of the normal component in x direction was measured with the use of two adjacent sensors. the tangential to the motion direction ( x) and the normal to the investigated surface ( z). Two components of the leakage were measured, i.e. The velocity was not constant during each measurement to imitate real operational conditions of the MFL tool. Experiments were performed for velocity of the MFL tool within the range of 0–2 m/s. The velocity effect on the magnetic flux leakage (MFL) signal was investigated in this paper.
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