Experiment Study On Stress-Magnetization Effect Of Metal Magnetic Memory Method Testing Technique

Metal Magnetic Memory testing (MMMT) method is based on stress-magnetic effect of ferromagnetic material (the magnetic properties of ferromagnetic material change, they are cased by stress). MMMT is a new nondestructive method to judge the damaging zone with concentrated stress in ferromagnetic items. Consequently, so far it is deemed to be a new nondestructive technique to diagnose the early damage in ferromagnetic items effectively. At the present time, MMMT is fasten on loading test, scene application and theoretical analysis,but MMMT technique microcosmic mechanism is still at junior step. So, in this paper, we based on the theory of magneto-physics, ferromagnetic, used theoretical analysis and experimental research methods to explore the mechanism of magnetic memory testing technology.Firstly, based on ferromagnetic science, magnetic physics theory and magnetic material system of energy, combined micro-damage Mechanics research on the ferromagnetic mechanical components, according to energy-minimization theory and one-dimensional landau-lifshitz equation,then to export relevant equations of magnetic domain and magnetic domain walls under different stress and also get numerical simulation. The results showed that the magnetic domain walls are mobile with a very small rate, without external stress or external magnetic fields of environment.20# steel, 45# steel and silicon steel sheet were conducted in the study, through the ANSYS finite element simulation of the stress test to determine the surface magnetic field measurement line. Specimens with a center hole defect were loaded under static tensile load. The magnetic flux leakage (MFL) of the surface specimens were measured under the magnetic measurement system. The influences of stress on magnetic flux league of ferromagnetic materials were studied. The results showed that, In case of slight deformation, it is because of the low accumulation of stress energy, that the MFL changes weakly around the hole of specimens. When there is a plastic deformation, high stress energy is accumulated and according to the Minimum Energy Principle, high stress concentration leads to the MFL distribution markedly. As the load increases, the magnetic inductionΔB increase, and the gradient curves K, the magnetic flux league of the defective parts, show significant fluctuations.Configured micro-magnetic colloid with excellent performance is very important, in order to observe magnetic domain structures of the loaded specimens with Bitter pattern method. Through the stress concentration of ferromagnetic components, where induced magnetic domain regions of directional and irreversible reorientation. Discussed that the magnetic domain of ferromagnetic component rearranged under the action of stress, the magnetic domain node is bound to appear in the stress concentration zone, and the correspondence between the stress and the magnetic domains. This work will provided a strong evidence to explain the magnetic memory effect of the micro-physical nature.