Estimation Of Subsurface Residual Stress Depth Profiles Via Wideband
Magnetic Barkhausen Noise Analysis And Correlative Stress Modeling
James Thomas, et al.
American Stress Technologies, Inc., USA
Abstract
Surface residual stresses in ferromagnetic materials can be evaluated non-destructively with Magnetic
Barkhausen noise (MBN). Residual stresses directly affect the magnetostrictive energy of a sample, thus
altering the way that magnetic domain walls move; this results in a quantifiable change in the MBN emitted by
the sample in the presence of an externally applied alternating magnetic field.
The effective depth of emission of MBN for traditionally used frequency bands is very near the surface,
hence the correlation between MBN properties and surface residual stresses. By analyzing a wider range of
frequencies the effective maximum depth of emission of a MBN signal can be estimated. As a result, an
approximate MBN-Depth relationship can be drawn.
Approximate MBN-Depth relationships are calculated and compared to residual stress depth profiles in this
study. Residual stress depth profiles are measured using X-Ray diffraction and electrochemical layer removal.
This report introduces a correlation-based model for estimation of residual stress profiles. This method is tested
for efficacy with several sample sets, including ground bearing rings, which yield accurate results within a
limited range of depths. Stress modeling via MBN is demonstrated to be an effective method for non-destructive
approximation of subsurface residual stresses.
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