A novel dynamic cold expansion method based on electromagnetic load was developed to enhance the fatigue life of open hole structures. The experiments were conducted to investigate the method

and the corresponding static cold expansion method was also investigated as comparison. The expansion resistance was evaluated. The geometric dimension varieties of holes after cold expansion were measured. Moreover

the fatigue life of specimens after both methods were assessed

and the fatigue failure and fatigue life enhancement mechanisms were discussed. The results show that dynamic cold expansion can obviously reduce expansion resistance compared with static cold expansion and generate more uniform hole diameter distribution along the hole axial direction after cold expansion. In fatigue tests

specimens worked by dynamic cold expansion method exhibited the higher fatigue life than that worked by static cold expansion method

especially under high load level. Furthermore

through fatigue fracture observed dynamic cold expansion specimen will often appear many fatigue source

general along the horizontal direction and the fatigue crack propagation

and the tradition of cold expansion specimen fatigue crack initiation in the entrance of mandrel and extend to the exit

that along the axial dynamic cold expansion method could get more even than the static methods of residual stress

therefore

the fatigue life of the open hole structure is improved.