Numerical Simulation And Experimental Research Of Stress Magnetism And Magnetization Reversal Effect On Ferromagnetic

Metal magnetic memory technology is a new magnetic non-destructive testing with great application potential, which can predict in advance the extent of damage of the ferromagnetic materials. Based on the basic principles and basic physical knowledge of the metal magnetic memory technology, it explores the mechanism and the variation law of stress magnetism and magnetization reversal effect of the metal magnetic memory technology via numerical simulation and experiments.Based on stress-magnetic coupling model of stress permeability, it conducts finite element simulation analysis on V-notch, semicircle notch and V-semicircle dual defects of 20# steel specimen by using the finite element analysis software ANSYS. The simulation results show that the stress concentration region of specimen, tangential component has a maximum value of leakage magnetic field, while normal component changes symbol and exceeds a zero. Also, the stress concentration degree on specimen with different gaps is not the same. The magnetic memory signal distribution is characterized by different peak, peak-peak width. Stress distribution contours of specimens show that stress concentration of axis areas of specimen with dual defects is much stronger than that of V-shaped notch and semicircle-notch specimen. The gradient value K(z) of evaluation features on magnetic memory signal will not apply on stress concentration area caused by the correlation function of double defects specimen.The simulation results also show that the relationship between the leakage magnetic field and stress is in the form of polygonal on the measurement point of each specimen. The leakage magnetic field flux decreases with stress and then increases. On the different measurement points of each specimen, the location of magnetization reversal point and the maximum variation of the magnetic field value ΔBmax have different changing laws. The ΔBmax is characterized by the stress sensitivity on measurement points of each specimen. Finally, the simulation analyses the influence law of stress-magnetic effect on ferromagnetic component by the measured path, the probe lift-off value.Carrying out a tensile test on 20# steel specimen with different V-notched angles, the results showed that with ferromagnetic component of different notch angles in different deformation stages, the distribution curve of the normal component Hp(y) of the magnetic memory signal exhibits different size of amplitude and nonlinearity, and with the increasing of the component notch angle, Hp(y) amplitude increases as well. Analytic result of the test shows that through characteristics of the distribution curve of magnetic memory can roughly judge the deformation stage of the specimen under the static tensile loads.By carrying out a tensile test on round-bar specimens of 40 Cr steel and 20# steel, it is found that relations between two kinds of ferromagnetic material component leakage magnetic field strength and the tensile stress are showing magnetization reversal phenomenon. Different ferromagnetic materials, the change curve shape of the leakage magnetic field and stress is different. The specific performance is the location of magnetization reversal point and the maximum variation of the magnetic field value ΔBmax have different changing laws. Secondly, the influence of magnetization reversal effect on ferromagnetic component with magnetization history effect is studied. The results showed that magnetization history effect does not affect the location of magnetization reversal point, but the maximum variation of the magnetic field value ΔBmax. Among them, the direction of magnetization influences the change direction of ΔBmax, no influence the rate of change.Finally, the stress equivalent magnetic field model and the stress magnetic permeability model of magnetization reversal effect are established. There are all very good reflect the phenomenon and basic characteristics of stress magnetization reversal effect, which is consistent with the experimental results.The above conclusions not only enrich the foundation theory of metal magnetic memory technology, but also promote heavily the quantitative evaluation system of metal magnetic memory testing.