Effect of sample size on the residual magnetic field of ferromagnetic steel subjected to tensile stress

Abstract

This research investigates the effect of sample size on the variation of the residual magnetic field (RMF) induced by tensile stress under the earth's magnetic field. Four sets of Q345 steel samples with different widths and thicknesses were tested in the laboratory. The correlation between the applied stress and the normal component of the residual magnetic signals, Hp(y), and its slope coefficient, K, were studied. The results show that there obviously exists a single-valued relationship between the applied tensile stress and the slope coefficient. The magnitude of K decreases with an increase in sample width or thickness under the same stress. The sample size affects the magnitude of the RMF instead of changing the magnetic curve's profile. The experimental results are explained by the theory of the interaction between dislocation and domain wall, as well as the theory of the demagnetising field. In addition, the sample size is proposed as one of the influencing variables in the classical Jiles-Atherton-Sablik (J-A-S) model theory of the magnetomechanical effect.