Magnetomechanical effects under applied stress and unloaded conditions measured by a probe with indirect pickup coil

A magnetic probe containing a yoke and indirect pickup coil was developed. The magnetic minor hysteresis loops of a low carbon steel sample were measured by using this probe during the loaded, reloaded and unloaded states of a tensile test. It was found that in the elastic region, the coercivity H_C decreases with increasing external stress due to domain reorientation, while in the plastic stage, it increases almost proportionally with external stress as the result of dislocation pinning effects. This result agrees well with that measured by Hall sensor and direct pickup coil. Under the reloaded condition after the cold working, H_C deceases more quickly at low stress because of the formation of texture substructure. The difference in H_C between the loaded and unloaded conditions, attributes to the effects of the applied stress and residual stress on domain wall motion.