INVESTIGATION OF THE STRESS-DEPENDENT MAGNETIC EASY-AXIS IN STEEL USING MAGNETIC BARKHAUSEN NOISE

Angular-dependent magnetic Barkhausen noise (MEN) measurements were pe rformed on a pipeline steel sample for various values of applied uniax ial stress at three angles with respect to the sample's zero stress ma gnetic easy axis direction. It was observed that the response of the M BN signal to stress was dependent upon the direction of the stress wit h respect to the zero stress easy axis. The stress response of the MBN signal was greatest for (i) tensile stresses oriented perpendicular t o the zero stress easy axis direction and (ii) compressive stresses ap plied parallel to the easy axis direction. The modification of the MBN signal under an applied stress was attributed primarily to a change i n the 180 degrees domain wall population in the material investigated. Results were described by a model that considered regions of locally correlated domain behavior, termed ''interaction regions,'' that were typically the size of grains within the steel material. A basic result of the model was the stress required to modify the number of 180 degr ees domain walls within an interaction region. Theoretical calculation s of these threshold stresses for a typical grain size were found to b e in agreement with the range of applied stresses that was observed to modify the angular-dependent MBN signal obtained from the sample. (C) 1996 American Institute of Physics.