Effect of applied stress on the reversible and irreversible differential permeabilities in 2% Mn pipeline steel

The contributions of reversible differential permeability (RDP) and irreversible differential permeability (IDP) to the total measured permeability have been derived from initial magnetization curves for a 2% Mn pipeline steel. In general, the effects of uniaxial stress on the IDP were significantly greater than on the RDP, and all the observed changes tended to be smaller at high magnetizations. At lower magnetization RDP tended to increase initially with tensile stress, while IDP was almost unaffected. On the other hand, compressive stress gave generally larger decreases both in RDP and IDP. The observed variations of RDP and IDP were, however, found to be complex functions of the magnetization.