Study on Characteristics of Magnetic Memory Signal of Q345R Steel during the Tensile Process

摘要

A systematic experiment research is carried out on the study of magnetic memory, aiming at the problem of quantitative relationship between the strain varying process and the magnetic memory signals. The Q345R steel was used as the object material. A large plate specimen was used to perform the magnetic memory test at typical deformation stages of the stretching process. In this paper, a mean local derivative (dH/dx) method is put forward in the mathematical characterization of magnetic signal, which can eliminate the interference of accidental factors effectively, and provide the variation pattern of the magnetic signal in different deformation stages. Results indicate that the magnetic memory signal has special sensitivity to the initial yielding stage of the material. The characteristic of this stage is that dH/dx experiences large fluctuation, whereas it does not necessarily get the maximum value. The mechanism of this phenomenon is that the non-uniform plastic strain changes the spontaneous magnetic field H_p inside the metal. In the elastic stage, H_p is linearly increasing with x, where dH/dx is almost constant. In the strengthening stage with uniform large deformation, H_p gradually becomes stable and tends to zero.