Determining Residual Stress Depth Profiles Using the Magnetic Barkhausen Effect

A new method for determining depth dependence of residual stress from measured magnetic Barkhausen signals is proposed. This method improves on the previously accepted practice, which rather loosely used Barkhausen measurements at different frequencies for nondestructively determining the depth dependence of properties. This paper develops a complete set of equations for describing the detected Barkhausen signals in terms of the actual emissions that are generated inside the material and how these appear when they propagate to the surface. The underlying equations consider the Barkhausen emission signal amplitude and its decay with distance and frequency. The variation of Barkhausen emission amplitude with stress is also described. A case study of depth profiling in a specimen that consists of multiple layers with different, but uniform, physical properties is presented.