Tube Bulging by Electromagnetic Forming Using Sheet Spiral Coil.

Tube bulging by electromagnetic forming using a new type of sheet spiral coil is proposed. Under various working conditions the effects of profile and forming efficiency are experimentally investigated. The number of turns of the coil, the length of the coil, the charged energy and the capacity of the capacitor bank are used as experimental parameters. The forming mechanism is clarified. As the number of turns of the coil increases, the amplitude of current waves and the period of current decrease. The bulge height is maximized within the range of number of turns of coil between 18∼30. The deformation of the tube bulge is reduced when the coil length increases. The fewer the turns of the coil and the smaller the capacity of the capacitor bank, the higher the forming efficiency. The forming efficiency becomes maximum at the current frequency of about 5kHz.