Influence of Lüders bands on magnetic Barkhausen noise and magnetic flux leakage signals

Abstract

Luders bands, which occur during the onset of tensile plastic strain in most steels, are localized regions of high plastic strain within a specimen, bounded by regions that have undergone mainly elastic deformation. This study was conducted to understand the dependence of magnetic Barkhausen noise (MBN) and magnetic flux leakage (MFL) signals on Luders banding in mild steel. MBN and MFL measurements were made on tensile samples of hot-rolled mild steel, in which Luders bands were deliberately nucleated by applying tensile stress. The results indicate that the MBN activity increases in the region of Luders bands. A strong magnetic anisotropy was also observed on these bands with the generation of dual magnetic easy axis. The MFL results indicate that magnetic flux leaks out into the air from regions with Luders bands due to decreasing permeability in these regions owing to localized plastic deformation.