Quantitative analysis of the relationship between non-uniform stresses and residual magnetizations under geomagnetic fields

Abstract

The quantitative relationship between non-uniform stresses and stress-induced residual magnetizations in ferromagnetic materials under geomagnetic fields was investigated. A ferromagnetic steel specimen with two symmetric notches was stretched to generate a non-uniform stress distribution. The residual leakage magnetic field and surface strain of the specimen were detected. Stress distribution was calculated according to the tested stress–strain curve of the material. The residual magnetization inside the specimen was reconstructed using residual leakage magnetic field signals. The quantitative relationship between stress and stress-induced residual magnetization was then established. Stress-induced residual magnetization was observed along the stress direction, and the intensity of the residual magnetization increased almost linearly with increasing stress.

Effect Model of Stress and Plastic Deformation on Conductivities of Various Magnetic Materials

“…Because of their effectiveness and convenience, electromagnetic Non Destructive Testing (NDT) methods, such as magnetic flux leakage testing [1], eddy current testing [2], [3], magnetic memory testing [4], magnetic Barkhausen noise testing [5], current field testing [6] and current potential drop testing [7], have been widely used to detect metalloss defect [8], [9], crack [10], [11] and especially some mechanical damages induced by stress, such as stress concentration [12]- [15], plastic deformation [16], [17], etc. The electromagnetic nondestructive testing of mechanical damage mainly depends on a physical phenomena that the mechanical stress and the dislocations induced the plastic deformation can change the magnetic and electric properties of the testing materials, which were described as the Magneto-Mechanical Effect (MME) [18] and the Electro-Mechanical Effect (EME) [19], respectively.…”

Stress-Induced Magnetic Anisotropy Model Under Unidirectional Tension

“…Yang et al [19] studied the influence of stress and external magnetic field on the residual magnetic field of ferromagnetic steel and found that the direction of the residual magnetic field is affected by the combined action of stress and external magnetic field. They also reconstructed the magnetization inside the structure by using surface magnetic field signals and found that stress-induced magnetization under geomagnetic field is directed along the stress and the intensity of the stress-induced magnetization is linearly related to the applied stress [20]- [22]. Sun et al found that stress-induced magnetic anisotropy is represented by stress dependence of magnetic permeability in different directions [23].…”