A novel system for non-destructive evaluation of surface stress in pipelines using rotational continuous magnetic Barkhausen noise

In the present work a new system for nondestructive evaluation of applied stress on the pipeline steels surface is proposed. This system is based on applying a magnetic field on the pipe surface, whose direction changes due to rotatory permanent magnets. The variation of magnetic field direction produces the Barkhausen signal, which is measured by a pick-up coil. The angular dependence of the magnetic Barkhausen noise signal energy is influenced by the pipe surface curvature due to the changing head-probe liftoff. Also, the said angular dependence changes with the applied tensile stress due to the magneto-elastic effect. The result of Barkhausen noise measurements in the pipeline surface submitted to applied tensile stress reveals that, since the effect of curvature on the angular dependence remains constant, the effect of applied stress could be determined by analyzing the angular dependence variation of the Barkhausen signal with the applied stress.