Magnetomechanical Acoustic Emission of Ferromagnetic Materials at Low Magnetization Levels (Type I Behavior),
CALIFORNIA UNIV LOS ANGELES DEPT OF MATERIALS SCIENCE AND ENGINEERING
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Magnetomechanical Acoustic Emission MAE intensities and waveforms were measured as a function of applied magnetic field for Fe, Ni and a number of Fe-Ni and Fe-Si alloys. MAE behavior has been correlated with various magnetic properties, including magnetic induction, magnetostriction, and rate of magnetic flux change. A direct proportionality was found between the initial saturation level of MAE intensity and magnetostriction. This is consistent with the prediction of a displacement model for MAE. MAE intensity was also found to vary linearly with magnetic induction at weak fields. Experimental results suggest that the motion of 90 deg domain boundaries is a source of MAE signals and that the MAE level is proportional to the volume fraction of magnetized domains separated by 90 deg boundaries. As magnetization proceeds, smaller domains become magnetized along the applied field, leading to a decrease in the volume of each domain wall jump. Thus, MAE intensity at these field levels tended to saturate. It is also shown that MAE and Barkhausen noise have substantially different characteristics even though both arise from discontinuous magnetization of materials. Author.
- Electricity and Magnetism