In this research, tensile tests of three different steels were carried out to characterize the variation of the residual magnetic signals. To reduce the impact of initial magnetic field, all of the specimens were demagnetized before loaded. It was observed that the variations of magnetic signals along the surface of these steels demonstrate different characteristics both in the elastic and plastic stages. In the elastic stage, the magnetic field variation of Q235 and 45# steels had a nonlinear relationship with the applied stress and a simple linear relationship between stress and magnetic field appeared in Q345 steel. In the plastic stage, the magnetic field variation of Q235 was very complex and the magnetic field variations of Q345 and 45# steels demonstrated a process of systematic evolution. In addition, there existed a local dent of the magnetic curve in the necking position of the sample. When the sample was finally ruptured, one may evaluate the fracture position according to the features of the magnetic curve. Possible reasons were given for the different characteristics of magnetic field variations in different steels.
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