抄録
Ferromagnetic materials are widely used for cars, trains, and ships. Because of their mechanical properties, iron and steel are popularly used for the frame materials. Nondestructive testing of iron and steel is an extremely important way of maintaining their mechanical reliability. It is well known fact that Barkhausen signals are only emitted from ferromagnetic materials having magnetic domain structures. Also these signals change their properties depending on their past mechanical as well as radioactive stress histories.
We applied a method of analyzing frequency fluctuations to the Barkhausen signals to detect the mechanical stresses. We unexpectedly succeeded in finding that applying frequency fluctuation analysis to the Barkhausen signal made it possible to detect the mechanical stress. This was fact confirmed by applying our method to the 30 test ferromagnetic materials. Further, the environmental noise problem essentially accompanying measurement of the Barkhausen signals were taken into account by applying this frequency fluctuation analysis method to environmental noise.
