Enhancing the electromagnetic forming performance of thin-walled sheet metal via a thicker driver: forming behavior and experimental validation

This paper proposes an innovative electromagnetic forming (EMF) approach for die-forming of sheet metal parts with a low thickness-to-diameter ratio, specifically set at 0.25%. This approach incorporates the use of an auxiliary driver sheet, strategically introduced to refine forming behavior. Numerical simulations reveal that the conventional EMF method fails to prevent wrinkling defects in thin-walled sheet metal forming, with the severity of wrinkles increasing as the voltage rises. These wrinkles reach a maximum height of 11.3 mm and result in inadequate workpiece adherence to the die. To mitigate these issues, the study proposes a novel technique that significantly reduces wrinkle formation through enhanced interaction between the driver sheet and the workpiece. A meticulous evaluation process led to the identification of an optimal driver sheet thickness of 3 mm, effectively reducing the wrinkle height to a mere 0.67 mm. This new method demonstrates superior forming accuracy and a closer adherence to the die contour when juxtaposed with conventional EMF approaches. Furthermore, the process window is defined by analyzing two fundamental process parameters: blank holder force (F_BHF) and discharge voltage (V_d). An in-depth investigation into the deformation history associated with the driver sheet EMF technique, particularly under conditions of V_d = 12 kV and F_BHF = 8 kN, revealed die-fitting gaps of 1.41 mm. Comparative experimental analysis further validates the effectiveness of this refined EMF method in manufacturing deep-cavity workpieces, evidencing superior forming accuracy with a maximum die-fitting gap of 1.41 mm and a wrinkle height limited to 0.67 mm. Consequently, this innovative driver sheet EMF approach is elucidated as providing notable enhancements in flexibility and efficiency for the manufacturing of extremely thin-walled sheet metal parts.