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

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.