Modeling the effects of torsional stress on hysteretic magnetization

Opposite torques applied axially to a polycrystalline ferromagnetic rod result in tensile and compressive stresses acting perpendicularly at the rod surface at 45° to the rod axis. These stresses affect the magnetization of the rod when a magnetic field is applied parallel to the rod axis. It is shown how one can formulate the magnetomechanical hysteresis model so as to treat this special case of biaxial stress and take into account the effect of opposite torques on the magnetic properties of the rod. Variation of hysteresis parameters such as coercive field, remanent flux density, differential permeability at the coercive field, and hysteresis loss as a function of applied torque are determined from the model. In the model, the torque is applied first and then the field is cycled to give hysteresis loops. It is found that the torque dependence of the magnetic properties is different, depending on what is chosen for H_max, the maximum value of the applied magnetic field H. The best parameter to use for tracking the torque is found to be H_c at saturation or near saturation, since that parameter shows an almost linear decrease with the applied torque