Enhancement method of magnetic flux leakage signals for rail track surface defect detection

Abstract

Magnetic flux leakage (MFL) detection is widely used for non‐destructive testing of rails, pipelines and storage tanks. The leakage magnetic field (LMF) of a defect, especially a small defect, is usually weak. To find small defects on the rail surface, here a ferrite is added in an LMF sensor to reduce the reluctance to increase the magnetic intensity above the defects. The effects of the cross‐sectional shape and size of a ferrite are studied by simulation and experiments, and the suitable dimensions for signal enhancement are found. To suppress the interference caused by the variation of the lift‐off distance, two Hall sensors are introduced and a differential circuit is designed for signal post‐processing. From the finite element simulation and experiments, it is shown that the MFL signals with a ferrite are significantly increased.