Barkhausen effect in steels and its dependence on surface condition

Abstract

Micromagnetic Barkhausen signals from magnetic materials originate from the discontinuous changes in magnetization under the action of a changing applied magnetic field.Barkhausen emissions that are detected by a sense coil come predominantly from a surface layer. In iron based materials this layer is about 500 μm thick. The Barkhausen signal is affected by changes in material microstructure and the presence of residual stress, since these affect the dynamics of domain wall motion. The selective attenuation of high frequency components of the Barkhausen signal due to eddy currents in electrically conducting materials is used to evaluate changes in material condition at different depths inside the material.Barkhausen measurements on specimens subjected to different thermal treatment during surface conditioning procedures are presented. Also presented for comparison are analysis of the material condition using x-ray diffraction for assessment of residual stress, and microhardness measurements which evaluate the surface microstructure condition. The results show that Barkhausen emissions can be utilized to evaluate changes in the surface condition of materials. Keywords Barkhausen effects, Materials modification, Materials analysis, Surface dynamics, Surface treatments Disciplines Electromagnetics and Photonics | Engineering Physics CommentsThe following article appeared in Journal of Applied Physics 81 (1997): 5085 and may be found at http://dx.doi.org/10.1063/1.364516. RightsCopyright 1997 Micromagnetic Barkhausen signals from magnetic materials originate from the discontinuous changes in magnetization under the action of a changing applied magnetic field. Barkhausen emissions that are detected by a sense coil come predominantly from a surface layer. In iron based materials this layer is about 500 m thick. The Barkhausen signal is affected by changes in material microstructure and the presence of residual stress, since these affect the dynamics of domain wall motion. The selective attenuation of high frequency components of the Barkhausen signal due to eddy currents in electrically conducting materials is used to evaluate changes in material condition at different depths inside the material. Barkhausen measurements on specimens subjected to different thermal treatment during surface conditioning procedures are presented. Also presented for comparison are analysis of the material condition using x-ray diffraction for assessment of residual stress, and microhardness measurements which evaluate the surface microstructure condition. The results show that Barkhausen emissions can be utilized to evaluate changes in the surface condition of materials.

Early corrosion detection in structural carbon steels using electromagnetic sensors

“…In the case of the Stress Proof Steel the deviation from the reduced area curve for the samples corroded for less than 10 minutes is slightly higher making the result less reliable. The positive deviation for corrosion times higher than 10 minutes can be attributed to the level of residual stresses near the surface and the variation in surface roughness [20][21][22]. Machining introduces a level of stresses on the surface of the sample which affects the dynamics of domain wall motion.…”

A model for the influence of microstructural defects on magnetic Barkhausen noise in plain steels

“…In MBN experiments, the signals obtained by the MBN sensor are filtered to eliminate the harmonics of the applied magnetic field presented in these signals [1][2][3][4][5][6][7][8][9][10][11][12][13]. In this process a band pass filter was used, as is described in Section 2.…”

“…This effect has been used as a nondestructive method to test the microstructure of magnetic materials [1][2][3][4].…”