Investigation of accurate forming of a semi-ellipsoidal shell part by an electromagnetic forming method

Forming a sheet into a predesigned die cavity is an effective way to improve the dimensional accuracy of deformed parts. However, it is difficult to obtain good die-fitting quality for workpiece deformed at high speed during the one-time discharge electromagnetic forming (EMF) process. To address this challenge, a numerical simulation model was established to help optimize the forming process that affects the die-fitting quality in the formation of a semi-ellipsoid shell part. Then, experiments were conducted according to the optimized forming process. Finally, the dynamic deformation behavior of the workpiece was revealed. The results showed that the drawing deformation mode can effectively improve the die-fitting quality as well as the effective plastic strain distribution of the shell part compared with the bulging deformation mode. Moreover, reducing the initial blank diameter is a more effective way to improve draw-in compared with adjusting the blank holder force. Furthermore, a semi-ellipsoid shell part was manufactured with a maximum die-fitting gap of no more than 1.4 mm at a one-time discharge voltage of 11.5 kV. The deviation was only 1.45% of the maximum forming height. The results provide a foundation for forming a large semi-ellipsoidal shell part by the one-time discharge EMF method.