A new SNR enhancement method in MFL detection for microcracks on rough surface based on the ferromagnetic lift-off layer

Abstract

ABSTRACT In conventional magnetic flux leakage (MFL) detection research, the surface of the workpiece is usually assumed to be smooth. However, the actual roughness will have an impact on the detection. To solve the problem of crack detection on rough surfaces, a method using ferromagnetic lift-off media instead of air lift-off was proposed. Firstly, the smooth surface and the rough surface model were established, and the difference of the leakage magnetic field signal was compared through the simulations. Secondly, the air lift-off media was replaced with ferromagnetic lift-off media, and the enhancement effect of the ferromagnetic lift-off media on the SNR(signal-to-noise ratio,SNR) of the magnetic flux leakage signal of microcrack was analyzed. Then, by changing the ferromagnetic media layer thickness and permeability, the improvement of the these parameters on SNR of the magnetic leakage signal of microcracks was analyzed. Finally, it was verified by experiments that the method can improve SNR of magnetic flux leakage signal of microcrack on the rough workpiece surface to a certain extent. The SNR enhancement method provides a certain application reference for the practice of magnetic flux leakage detection of rough surface workpieces.