Coupled mechanical-magnetic analysis of cut-edge damage in thin sheet electrical steels

Thin electrical steel sheets are extensively used in electric machine cores owing to their high magnetic permeability and low core losses. Blanking is the predominant manufacturing process for laminations in high-volume applications due to its efficiency and well-controlled parameters; however, localised deformation at the cut edge can adversely affect the magnetic performance. This study systematically examines the influence of blanking on the magnetic behaviour of a non-grain-oriented 3.2% Si electrical steel. The effects of sheet thickness, shear localisation, and fracture mechanisms are investigated through combined experimental and numerical approaches. A novel finite element model is developed for this class of material to directly correlate mechanical deformation with magnetic response, considering blanking-induced strain, strain-rate, and geometric dislocations attributed to non-local effects. A new formulation is introduced to correlate the magnetic permeability with the deformation-induced microstructural changes. In-situ blanking trials with digital image correlation, nano-indentation, and microstructural characterisation were used to validate the model. Magnetic hysteresis and magnetisation measurements using a single-sheet tester reveal that tensile residual stresses markedly reduce permeability, while both tensile and compressive stresses increase magnetic losses through inhibited domain mobility and grain-boundary pinning. The proposed model achieves an over 90% predictive accuracy with experimental measurements, providing a predictive tool for optimising blanking parameters and enhancing electromagnetic efficiency in advanced energy systems.