Statistical properties of magnetization discontinuities in technical steels

On-Line Inspection of Ferromagnetic Materials Using Magnetic NDE Methods

“…In general, their results also showed that the total number of magnetic Barkhausen noise pulses increased with increasing grain size in commercial steel [5]. In subsequent work [6], the total number of the magnetic Barkhausen noises and, in addition, MAE pulses, has been found to increase with increasing grain size in decarburized steel, in agreement with [2][3][4][5]. This indicates that the Barkhausen activity of both 180° domain walls and non-180° domain walls (90° in steel) increases in general with increasing grain size in steels.…”

“…Results in Figs. 4 and 5 indicate, in general, that the magnetic Barkhausen as well as MAE signals in nickel,•are sensitive to the grain size. Noticeable is the double peak structure observed in each case.…”

“…For small grained materials, the nucleation rate of domains should be higher due to a larger density of available nucleation sites, i.e., The lack of magnetic Barkhausen and MAE signals at field H ~ He, in Figs. 4 and 5 respectively, is probably due to the presence of reversible domain wall translation as the dominant process for magnetization change. It has been observed in steel [2] that the size of domains increase with grain size.…”

“…One class of recently developed instruments for the nondestructive measurement of grain size make use of the magnetic Barkhausen effect [2][3][4][5]. However, these are calibrated empirically, since no theoretical interpretation of the dependence of the magnetic Barkhausen effect on grain size has been given.…”