Revisiting the Universality Law in Magnetically Detected Residual Stresses in Steels

The dependence of residual stresses on differential permeability, determining the so called Magnetic Stress Calibration (MASC) curve, results in the Universal MASC curve after normalizing the stress and permeability axes with the yield stress and the maximum differential permeability of the steel under test, respectively. The motivation of this paper is to illustrate the ability of obtaining the MASC curve of an unknown steel just by measuring its yield stress and maximum differential permeability. The calculated MASC curve of an unknown type of steel, obtained by multiplying the stress and permeability axes of the Universal MASC curve with the yield stress and maximum differential permeability obtained by the stress-strain curve under simultaneous measurement of the permeability, was compared with the actual MASC curve of the same unknown type of steel determined by the classical method, with an agreement better than ±5%. The conclusion is that the actual MASC curve of an unknown type of steel can be determined just by a stress-strain measurement, with simultaneous determination of the maximum amplitude of the differential permeability.