Estimation of the magnetic pressure in tube expansion by electromagnetic forming

In the analysis of electromagnetic forming processes it is essential to be able to estimate the magnetic pressure acting on the workpiece. For this purpose the analysis of the equivalent electric circuit has been used widely. In this approach, it was assumed that the workpiece and the forming coil are so long that the end effect can be neglected, which is far from actual practice. Recently, the finite-element analysis of the electromagnetic field has been used by the present authors to obtain a more realistic pressure distribution, In this work, the analysis has been extended to investigate the effects of the geometry of the electromagnetic forming system and the resistivity of the workpiece on the magnetic pressure in tube expansion. The magnetic pressure varies with the geometric parameters of the electromagnetic forming system as predicted by circuit analysis, but the magnitude of the variation depends on the resistivity of the workpiece. The magnetic pressure decreases as the tube length increases. However, there is a limiting length above which the pressure no longer decreases. This length is almost equal to the length of the forming coil.