Quantitative representation of magnetic memory signal

The modified J-A model that describes the magnetization intensity inside the material was used in the metal magnetic memory (MMM) phenomenon analysis. However, the MMM signal reflected the magnetic field outside the material. The relationship between the magnetization intensity and the MMM signal outside the material was established. First, the tensile fatigue test was conducted to study the distribution and variation characters of the MMM signal outside the damage area. Then, according to the experimental results, a magnetic dipole model was constructed to describe the scattering magnetic field. After that, the scattering magnetic field was related to the magnetization parameter M₀ in the modified J-A model, and the MMM signal was described quantitatively. The research results show that the bar-type damage concentration area becomes the interior magnetic source and scatter magnetic field outside; that the scattering magnetic field at a certain point outside the specimen is decided by the magnetic charge density and size of damage concentration area, the magnetic charge density of crack, the size and location of crack, and the location of this point; and that the scattering magnetic field varies with the magnetic charge density of damage concentration area, the magnetic charge density of crack, and the size of crack. The magnetic charge density of damage concentration area has a linear increase relation with M₀, and the magnetic charge density of crack has a linear relation with M₀ and relates with crack size. The distribution and distribution variation characters of magnetic field described by the magnetic dipole model are in accordance with the experimental results. And the quantitatively relational expression among the MMM signal, stress, material damage situation and crack impact factor is obtained based on the magnetic dipole model and the modified J-A model.