Plastic deformation effects on magnetic Barkhausen noise

Plastically deformed steel specimens were analyzed using surface magnetic Barkhausen noise (MBN). Three types of samples were investigated: mild steel specimens uniaxially deformed up to 40% strain, mild steel specimens deformed in bending to 0.2% longitudinal strain, cold-rolled nuclear reactor pressure vessel steel specimens from 0% to 60% reduction ratio. The angular dependence of an 'MBNenergy' term was used to examine magnetic anisotropy changes with increasing deformation, with linear MBN scans used to monitor changes in magnetic properties along the specimen axis. Average MBNenergy values were observe to vary significantly with stress within the elastic region, yet only slightly in the plastic range of deformation. Changes in the shape of the pulse height distribution curves were evidence of plastic deformation effects on domain wall pinning sites. We conclude that a complex interplay between stress and strain mechanisms, residual stresses and crystallographic texture generates variations in MBN signal