THE EFFECTS OF BIAXIAL STRESS ON BARKHAUSEN NOISE SIGNALS WHEN THE MAGNETIC-FIELD IS NONCOAXIAL WITH THE STRESS AXES

The Barkhausen noise amplitude was measured under conditions of biaxia l stress in steel pipe for the case of a magnetic field noncoaxial wit h the stress axes. The stress axes for stresses sigma(1) and sigma(2) were orthogonal to each other. In particular, sigma(1) was the axial s tress and sigma(2) was the hoop stress. Various angles were used for t he field direction, along with various stress magnitudes, both compres sive and tensile. The stress sigma(2) was always tensile, but sigma(1) was both compressive and tensile. A model for this biaxial stress sit uation, based on the Sablik-Jiles magnetomechanical model, was formula ted. Using a model for the Barkhausen noise deriving from the Alessand ro et al. model, the Barkhausen noise power maximum amplitude was comp uted for various field angles and stresses sigma(1) and sigma(2). The numerical results from this model calculation agreed qualitatively wit h many features of the experimental results. Thus, one found both nume rically and experimentally that with field direction at small angles f rom the sigma(1) axis, the Barkhausen noise amplitude increased as the stress sigma(1) was increased from negative to positive. At large ang les (generally greater than 45 degrees), the reverse was true and the Barkhausen noise amplitude decreased as stress sigma(1) was increased. Also, the curves for the various angles tended to intersect when sigm a(1) was set equal sigma(2). Differences between numerical and experim ental results are discussed, and suggestions are made for further impr ovement of the modeling. (C) 1998 American Institute of Physics. [S002 1-8979(98)09123-3].