A numerical model for the search of the optimum frequency in electromagnetic metal forming

Electromagnetic forming (EMF) is a high velocity forming technique that reshapes electrically conductive materials by abruptly discharging a bank of capacitors through a coil. The oscillation frequency of the discharge is a key parameter in the design of an EMF system. For a given initial stored energy, there exist a frequency that produces the maximum workpiece deformation. Once we know it, we can set the electrical parameters of the EMF system to make the current intensity oscillate with this optimum frequency. This saves energy and money, preventing also the premature wearing of the coil. The objective of the present paper is to find the optimum frequency of an EMF system. Using the results provided by a finite element model in frequency domain, we are able to obtain the current flowing trough the coil, the Lorentz force acting on the workpiece, a function relating the electrical parameters of the EMF system with frequency and the optimum frequency of the discharge. Our approach can be very useful for coil design and for modeling complex three-dimensional geometries. To validate the method presented here, we apply it to tube compression and tube expansion processes and compare our results with those provided by other authors.