Peculiarities of Internal Stress Measurement in Ferromagnetic Materials Using Barkhausen Effect and Other Magnetic Techniques

The transition from non-destructive evaluation of stress to NDT measurement of internal stress tensor components is challenging step considering and compensation of influencing factors during both calibration and measurement steps. The main influencing factors in ferromagnetic steels are material microstructure, self-interaction of principle stress tensor components and surface layers condition. This study shows experimentally the nature of those uncertainties. Some main features of surface treating influence on the stress measurements are considered, and the invariance of the magnetic Barkhausen effect method relatively to any changes of spherical strain/stress tensor component. The Barkhausen noise intensity depends only on the shear stress tensor component and the spherical stress tensor is influenced only by the material microstructure. The disregard of this regularity leads to available uncertainty in stress evaluation via the Barkhausen effect method.
Keywords: internal stress, deformation, surface structure, stress-strain state, Barkhausen noise, calibration curve, 3D-chart