Effect of Stress and Grain Structures on Dynamic Properties of Magnetic Domains

Recently, emerging magneto-optical imaging technique, especially the visualization of the dynamic properties of magnetic domains, provides a new magnetic detection method for assessing the stress state in ferromagnetic materials. In order to investigate the influence of stress and grain structure/grain boundaries on the dynamic properties of the magnetic domains, a magneto-optical imaging system is used to observe the variations of magnetic domain structure of grain-oriented silicon steel sheets under different stresses and applied magnetic fields. The experimental results show that the number of additional domains decreases, which also changes from point-like lancet domains to sab-like domains under the stress. And with strengthened stress, the magnetic domain is refined, and its average width decreases. With external magnetic field, the magnetic domains are rotated to the direction of the magnetic field, alongside enlarged area of the domains parallel to the applied magnetic field. Moreover, the grain structure, internal magnetic anisotropy as well as pinning effect at grain boundaries can affect the magnetic domain structure and domain wall motion. The results help to clarify the magnetoelastic coupling effect of ferromagnetic components, and the microphysical mechanism of magnetic detection technology, thus providing an important scientific basis for improving the sensitivity and reliability of stress assessment.