Experimental and finite element study of the effect of force distribution on electromagnetic pre-forming of aluminum alloy conical sheet parts

In forming conical parts by traditional deep drawing techniques, due to the stress concentration at the contact area between the punch and the workpiece, thinning and rupture occurs on the sheet. There is also a high possibility of wrinkling in the free area of ​​the sheet; where there is no contact between the punch and the sheet. Therefore, new methods have been examined in forming this group of parts. Electromagnetic forming is one of the relatively old methods of high-speed forming that has attracted more attention in recent years. In the present study, the process of pre-forming of aluminum conical parts using electromagnetic force has been discussed numerically and experimentally. First, experiments were carried out by a simple spiral coil and after confirming the validity of the numerical simulations, the effect of electromagnetic force density in radial and axial directions was investigated in different areas of the sheet. Using the obtained results, a new coil was designed and built that has the ability to provide suitable distribution of the force in the radial and axial directions. Reduction in power consumption by up to a quarter, an increase in the amount of radial inward force and the height of the preform formed cone up to 2 times, minimizing the friction force, reduction of the workpiece center thinning by 3% (while increasing the height by 2 times) and elimination of wrinkles in the flange area of the sheet are the advantages of using the new coil compared to the primary coil.