Magnetic rotational permeability for tensile stress evaluation of non-oriented electrical steel

Unlike unidirectional magnetization, characterized by fundamentally irreversible domain wall motion, limited coherent domain rotation, and increasing power losses, rotational magnetization offers preferential access to mechanisms that remain poorly investigated in the context of nondestructive testing (NDT). At low fields, rotational magnetization induces reversible 90° domain wall motion, which is sensitive to mechanical strain, while at high fields it is governed primarily by magnetocrystalline anisotropy and mechanical stress through magneto-elastic energy. The magnetic response under rotational magnetization thus emerges as a powerful means of observing stress effects and indirectly evaluating them. In this study, we implement a magneto-mechanical characterization setup, termed Magnetic Rotational Permeability (MRP), which combines two coaxially aligned eddy-current transducer (ECT) pick-up coils in a transmission–reception configuration with a rotational magnetic excitation field applied to a non-grain-oriented electrical steel sample under uniaxial tensile stress. The distinctive contributions of rotational magnetization mechanisms at low and high field levels were studied under varying stress conditions. Our results demonstrate that leveraging rotational magnetization mechanisms enables an indirect and reliable assessment of uniaxial tensile stress. We conclude by discussing these findings and outlining perspectives for the application of rotational magnetic fields in NDT.