Discussion of modified Jiles-Atherton model including dislocations and plastic strain

In metal magnetic memory (MMM) detection, the Jiles-Atherton model describes material magnetization caused by the geomagnetic field and cyclic stress. However, characterization of the effects of fatigue damage on magnetization remains an issue. In this paper, an expression for magnetization intensity M0 related to dislocation and plastic strain amplitude ep was incorporated into a modified Jiles-Atherton model. To validate the M0 expression, standard tensile fatigue tests were performed. Results indicate that the domain wall pinning parameter k1 in M0 is linear in both dislocation density ρ and average dislocations slippage distance ¯ λ, as is also the shear plastic strain amplitude in the stress control fatigue. The stress amplitude in strain control fatigue however is linear with respect to ρ 1/2 . Therefore, M0 can be expressed as a function of stress and ep (orand stress amplitude). Experiments showed that calculated M0 variations in fatigue development processes can reflect a variation law in the MMM signal, with certain differences. There is a numerical difference between Hpx and M0 because the surface magnetic field is much weaker than that within the ferromagnetic material. Hpx increases after macro crack initiation caused by an additional material demagnetization field and a leakage field near the crack during cracking.

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