Strain distribution visualization of punched electrical steel sheets using neutron Bragg-edge transmission imaging

Sasada, Seiji*; Takahashi, Yoshihito*; Takeuchi, Keisuke*; Hiroi, Kosuke  ; Su, Y. H.  ; Shinohara, Takenao   ; Watanabe, Kenichi*; Uritani, Akira*

Residual strains in a punched electrical steel sheet increase the iron loss in the steel sheet. To accurately estimate the effect of residual strain on iron loss, the residual strain distribution in a punched electrical steel sheet should be evaluated. In this study, we demonstrated the two- dimensional imaging of the residual strain distribution in a punched electrical steel sheet using the neutron Bragg-edge transmission imaging method. To improve the accuracy of strain measurement with minimal deterioration of spatial resolution, we applied a process of superposing many specimen images. The tensile strain near the punched edge and the compressive strain inside the core were experimentally confirmed using this method. Finally, the neutron Bragg-edge imaging results and those obtained from kernel average misorientation map using electron backscattered diffraction were compared to verify the validity of the proposed method.