Magnetic memory signals variation induced by applied magnetic field and static tensile stress in ferromagnetic steel

Abstract Stress can induce a spontaneous magnetic field in ferromagnetic steel under the excitation of geomagnetic field. In order to investigate the impact of applied magnetic field and tensile stress on variation of the residual magnetic signals on the surface of ferromagnetic materials, static tensile tests of Q235 structural steel were carried out, with the normal component of the residual magnetic signals, H p ( y ), induced by applied magnetic fields with different intensities measured through the tensile tests. The H p ( y ), its slope coefficient K S and maximum gradient K max changing with the applied magnetic field H and tensile stress were observed. Results show that the magnitude of H p ( y ) and its slope coefficient K S increase linearly with the increase of stress in the elastic deformation stage. Under yield stress, H p ( y ) and K S reach its maximum, and then decrease slightly with further increase of stress. Applied magnetic field affects the magnitude of H p ( y ) instead of changing the signal curve′s profile; and the magnitude of H p ( y ), K S , K max and the change rate of K S increase with the increase of applied magnetic field. The phenomenon is also discussed from the viewpoint of magnetic charge in ferromagnetic materials.