Improving the fatigue performance of AZ31 sheet with hole via electromagnetic cold expansion process

Improving the fatigue life of hole components is very important since cracks are often initiated from the hole wall due to stress concentration. In this study, the non-contacting electromagnetic cold expansion process (EMCE) was employed to improve the fatigue life of the AZ31 sheet with fastening hole. Simulation was done to investigate the distribution of residual stress and strain around the hole during the EMCE process. The effect of EMCE process on the surface integrity of the hole specimen was investigated via 3D super depth digital microscope. EBSD was utilized to observe the deformation and grain size distribution near the hole edge. Fatigue test was done to verify the feasibility of EMCE process on improving the fatigue life of thin AZ31 sheet specimen, and the fatigue fracture was observed by SEM. Results showed that the EMCE process can improve the fatigue life and fatigue limit of the AZ31 specimen. The specimen treated by EMCE process showed well surface integrity, and grain refinement was observed near the hole edge.