Magnetic signals of stress concentration detected in different magnetic environment

摘要

Stress concentration will generate a weak field leakage on the surface of ferromagnetic materials in the geomagnetic field because of the magneto-mechanical effect. Therefore, stress concentration can be evaluated by detecting the magnetic field on the surface of metal parts. This method has become an interesting focus to NDT researchers for its high sensitivity of magnetic field and no need of artificial magnetisation. However, this method also depends on the environmental magnetic field during detection. Although the stress status is the same, the testing results can be different because of the magnetic environment. With experiments in which a magnetic abnormality is generated by stress concentration in a nearly zero magnetic field but detected in another level of environmental magnetic field, the relationship between magnetic signals of stress concentration and the magnetic environment is investigated in this paper. The results show that the magnetic distribution depends on both the stress status and the environmental magnetic field. But these two factors often have quite different mechanisms; the distribution of magnetic field depends on the powerful one.