Velocity effect analysis of dynamic magnetization in high speed magnetic flux leakage inspection

•Dynamic magnetization and magnetic hysteresis in high-speed MFL were investigated.•Short magnetizing duration leads to the decrease of permeability of specimen.•Velocity effect will alter the leakage magnetic field and influence MFL signals.•MFL technique can achieve effective inspection with the speed of about 200 km/h.

The investigation described in this paper focuses on the velocity effect of dynamic magnetization and magnetic hysteresis due to rapid relative motion between magnetizer and measured specimens in high-speed magnetic flux leakage (MFL) inspection. Magnetization intensity and permeability of ferromagnetic materials along with the duration of dynamic magnetization process were analyzed. Alteration of the intensity and distribution of magnetic field leakage caused by permeability of specimen were investigated via theoretical analysis and finite-element method (FEM) combined with the actual high-speed MFL test. Following this, a specially designed experimental platform, in which motion velocity is within the range of 5 m/s–55 m/s, was employed to verify the velocity effect and probability of a high-speed MFL test. Preliminary results indicate that the MFL technique can achieve effective defect inspection at high speeds with the maximum inspection speed of about 200 km/h being verified under laboratory conditions.