An incremental processing method for large thin-walled ring shells: Electromagnetic incremental assembly

This study proposed an innovative incremental processing method named electromagnetic incremental assembly (EMIA), inspired by the concept of electromagnetic incremental forming (EMIF). The method addressed the support requirements for segmented assembly structures in large thin-walled ring shells. The study employed an assembly structure made of rigid polyurethane foams (RPUFs) with an irregular cross-section to support a large 5A06 aluminum alloy ring skin with a thickness of 1.5 mm during EMIF processing. This approach achieved a precise fit and effective support between the skin and the assembly structure. The study utilized a combination of numerical simulations and process experiments to the feasibility of EMIA. The study analyzed the effects of discharge voltage, discharge frequency, and coil position parameters on the assembly outcome. The results indicated that increased discharge voltage generally correlated with a decreased fitting gap. Parameters of discharge frequency and coil position primarily affected the profile fluctuation of the formed skin. Thus, these parameters influenced the maximum compression of the foam. The optimal process parameters, determined through simulations and experiments were a discharge voltage of 11.5 kV, three discharge steps, and a coil position spacing of 20 mm per discharge step. These parameters ensured a tight fit of the formed skin with the assembled foams, achieving a profile fluctuation of only 0.57 mm. Numerical simulation, further reviewed the dynamic deformation behaviors of the skin and foam, indicating that the compressive strain at the skin edges was 55.3 % higher compared with the middle region, thereby making the foam more susceptible to damage. The local region of the skin with a smaller initial gap to the foam collided with the foam sooner, thereby resulting in a shorter duration of plastic deformation and greater compression on the foam.