Expansion of a low conductive metal tube by an electromagnetic forming process: Finite element modeling

The expansion of a metal tube by means of an electromagnetic forming (EMF) process is attractive because EMF has a high forming rate and can reduce residual stress. The forming forces in EMF are Lorentz forces. They are derived from a repulsive interaction between a transient electric current induced in a coil with the aid of a capacitor bank and an eddy current induced in a metal tube by means of a transient current. Highly conductive metals are suitable for EMF-based tube expansion but tubes of low conductive metals are often used for industrial purposes. We studied various methods of using EMF to increase the formability of low conductive metals. In particular, we used a finite element method to compute an electromagnetic field coupled with temperature and deformation of a metal tube. Our results show that a highly conductive layer can increase the formability of a low conductive metal.