Review of Progress in Quantitative Nondestructive Evaluation
This paper reports on a recent study aimed at developing the stress-induced magnetic anisotropy (SMA) technique for characterizing residual stresses in case hardened steel components. The results of SMA measurements performed on flat induction hardened steel discs with different case depths confirm the feasibility of detecting principal stress axes by measuring the angular variation of magnetic permeability. The permeability signals along the principal axes were found to vary monotonically with the residual stresses measured by XRD, but the signals are in general smaller for samples with a larger case depth. The magnetomechanical properties of the martensitic case and ferritic/pearlitic core of the induction hardened sample were studied by measuring magnetostriction curves from strip samples that were cut from the case and core regions, respectively. The case strip shows a significantly lower magnetostriction than the core strip, indicating a weaker stress dependence of magnetic properties for the martensitic case than for the ferritic/pearlitic bulk of the case hardened samples.
American Institute of Physics
Lo, Chester C.H., "Nondestructive evaluation of residual stresses in case hardened steels by magnetic anisotropy measurements" (2011). Center for Nondestructive Evaluation Conference Papers, Posters and Presentations. 21.