Magnetic loss reduction in angularly stacked grain-oriented steel cores under normal compressive stress

The effect of compressive stress applied normal to the lamination surface on magnetic behavior is investigated in stacked grain-oriented Fe–Si ring cores with controlled angular misalignment between rolling directions (RDs) in neighboring layers. Three angular configurations, θ=0°, 60°, and 90°, are examined under normal stress levels up to 6 MPa. Magnetic characterization combines AC loss measurements with first-order reversal curve (FORC) analysis to resolve stress-induced changes in domain wall dynamics. The results reveal that relatively low normal compressive stresses (∼0.5–2 MPa) can significantly reduce magnetic losses at power frequencies, primarily through suppression of excess loss associated with dynamic domain wall motion. FORC fingerprints indicate that lower normal stress promotes magnetically softer processes governed by 180° domain walls, while higher stresses progressively broaden the distribution of switching fields. The loss-reducing effect of normal stress is most pronounced in non-shifted and moderately shifted configurations and weakens with increasing angular misalignment. These findings demonstrate that normal compressive stress, often unavoidable in practical core assemblies, can act as an effective loss-reducing factor when combined with appropriate lamination topology.