Tracking the propagation of Lüders bands in Q235 steel using high-resolution MBN imaging

Lüders bands are localised plastic deformation features that develop during the yielding stage of low-carbon steels and can markedly influence forming stability and structural performance. In this work, Lüders band propagation in Q235 hot-rolled steel under uniaxial tensile loading was investigated using digital image correlation (DIC) and high-resolution magnetic Barkhausen noise (MBN) imaging. A magnetic-head-based MBN sensor with sub-millimetre spatial resolution was employed to scan the specimen surface, enabling spatially resolved characterisation of magnetic features associated with Lüders band evolution. The spatial distribution of the MBN peak-position parameter showed good agreement with the strain field measured by DIC, allowing clear identification of both the initiation and propagation of Lüders bands. These results demonstrate that high-resolution MBN imaging provides a magnetic characterisation approach for detecting the propagation behaviour of Lüders bands.