Current frequency effect on electromagnetic tube expansion

Abstract

The frequency of capacitor discharge current is an important parameter in the electromagnetic forming process. In the present work, simulation and experimental study of electromagnetic expansion is carried out on aluminium tubes (Al 5052). The aim is to obtain the optimum frequency of discharge current that gives maximum tube expansion at constant discharge energy. A two-dimensional axisymmetric numerical simulation model is developed that couples electromagnetic and structural phenomenon sequentially. After validating experimental tube expansion results with numerical results, the simulation model is used to analyse the effect of variation in current frequency on the tube expansion. It is observed that maximum tube expansion and higher process efficiency occurred at 5 kHz, which is considered as the optimum frequency for the used experimental set-up. In contrast to sheet forming case observed in the literature, results of tube expansion show that maximum forming is obtained at a frequency where the ratio of skin depth to tube thickness is less than 1. It is also noticed that the optimum frequency depends on the inductance and resistance of the system.