The effect of loading speed on the residual magnetic field of ferromagnetic steels subjected to tensile stress

Measuring the residual magnetic field provides a promising tool for evaluating stress in ferromagnetic materials. Under the excitation of the geomagnetic field, stress can induce spontaneous magnetic signals in ferromagnetic materials, which can be used potentially to evaluate the stress concentration. However, different tensile loading speeds have an obvious impact on the spontaneous magnetic signals and an ignorance will result in inaccurately or incorrectly estimating the degree of damage of ferromagnetic components. In this paper, tensile tests were performed on 45# and Q235 steel specimens. Magnetic signals under different tensile loading speeds were measured to investigate the effect of loading speeds on the residual magnetic signals. The results indicate that the variations of the residual magnetic field due to different loading speeds change systematically as the applied load increases. There exists a correlation between the variation of the residual magnetic field, tensile loading speed and stress level.