Research On Metal Magnetic Memory Testing Technique And Its Applications

Due to the magnetic mechanical effect, the magnetic properties of ferromagnetic materials can change under the applied stress or residual strain. In this paper, the magnetomechanical effect model of ferromagnetic materials, which is under the unidirectional stress and in the elastic and plastic stage, are deduced referring to the model of Jiles-Atherton and Sablik. The transformations of the magnetic properties of ferromagnetic materials (Magnetic Permeability and Coercive Force) under applied stress and plastic deformation are obtained by calculating. This paper also studies the diversified affecting factors of the magnetic memory signal, such as the dimension of the stress concentration area, lift-off value, depth of the defect and buried depth of defect, by setting up3dimensional numerical model.Refering to the established magnetic mechanical model, this paper studies the Magnetic-Force Coupling Analysis systematically by ANSYS. The analysis researches the effects of several factors to the Metal Magnetic Memory Phenomenon, including different deformation stages (elastic deformation stage and plastic deformation stage), geometrical characteristic (depth and width of defect) and lift-off value.This paper reveals the relationships between the characteristic of magnetic memory signals and the deformation of specimens, which are made of Q345steel and added defects artificially.At last, this paper validates the engineering applied value of magnetic measurement technology by monitoring on-line magnetic for steel pipe nodes under compression load and by analyzing the relationship between the dimensions of the defects on the steel pipe specimens and magnetic memory signals.