Effects of isofield uniaxial cyclic stress on the magnetization of2% Mn pipeline steel - behavior on minor hysteresis loops and smallmajor hysteresis loops

The present results show that the sense of the stress-induced irreversible changes in the unstressed magnetization is not always towards the anhysteretic. Examples where the change is away from the anhysteretic are shown, as well as cases where the cyclic uniaxial stress does not cause an irreversible change in the sample's unstressed magnetization when that magnetization does not coincide with a point along the anhysteretic curve. Examination of the magnetization changes with cyclic stress along the upper or lower branches of a minor hysteresis loop suggests that the distance along that branch from the previous turning point is the most important factor in determining the sense of the stress-induced changes in magnetization. Initially the stress-induced changes in the unstressed magnetization occur in the same sense as they would have before the turning point, but the interaction between the domain walls and the pinning sites in the sample as the applied magnetic field changes after the turning point causes this stress-induced change to decrease in value and then reverse in sign. This suggests that the isofield cyclic stress-induced changes in the magnetization should be considered to be towards a local equilibrium condition rather than a global equilibrium condition (the anhysteretic curve)