Effect of tensile plastic deformations on the residual magnetization and initial permeability of low-carbon steels

The behavior of residual magnetization M r , initial magnetic permeability μ, and coercive force H c of steels subjected to plastic extension both in the loaded state and in the unloaded state during “slow” and “fast” loading is explained from a unified point of view. It is shown that, upon unloading, the appearance of residual compressive stresses along the direction of the applied force in a considerable portion of grains leads to an abrupt decrease in M r and μ and to an equally sharp increase in H c . A slow decrease in M r and μ and an equally slow increase in H c are observed in the loaded state with an increase in ε; this effect is caused by an increase in the dislocation density. The values of M r , μ, and H c in the transition region of ε ≤ εcr obtained under slow loading differ considerably from those obtained under fast loading. In loaded and unloaded states, the dependences of M r , μ, and H c on ε are identical at ε ≥ εcr. The results obtained will be important when the magnetic parameters analyzed in this study are used for nondestructive testing of steel structures that have plastic deformations.