Barkhausen noise measurement and its applications

One of the non-destructive methods for evaluation of stresses in steel is based on the dependence of magnetic Barkhausen noise (MBN) parameters upon the stress. Barkhausen noise is induced in a coil near the surface of the ferromagnetic object under investigation. A variable magnetic field of appropriate strength must be created in the object. This is achieved by: means of electromagnetic yoke manually pressed to the steel at the point of measurement. This paper discusses the problems of excitation stabilisation when calibration and measurement must be carried out with the different volumes or geometric dimensions of the material. MBN envelope magnitude and power were used as parameters for building calibration curves. Their suitability for this type of task was compared. Sensitivity of envelope shape in respect to the chemical structure and treatment of steel was also illustrated. As a result of investigations, a portable magnetic characteristics rester has been developed to help in the field inspections of binding force of cathode ray tubes (CRT). In CRT production technology steel tapes are wound around the TV glass panel. It is important to ensure a particular binding force, since its deflections might influence security parameters of a CRT. A non-destructive and rapid measurement method is highly desirable in this task.