Variation of stress-induced magnetic signals during tensile testing of ferromagnetic steels

Stress alone applied to ferromagnetic materials can induce the generation of weak magnetic signals on their surfaces, which can be potentially used to estimate the degree of damage of ferromagnetic components. In this paper, the normal component of stress-induced magnetic field, Hp(y), was measured during tensile tests on the surfaces of sheet specimens of three ferromagnetic materials. It has been concluded that Hp(y) depends on the applied stress and will present different characteristics on the elastic and plastic deformation stages, respectively. The phenomenon of sharp changes in magnetic signals occurring at the instant of fracture was also discussed from the view of the interaction energy in a ferromagnet.