Analytical approach for magnetic pulse welding of sheet connections

An analytical model to calculate the acting forming pressure in magnetic pulse welding by determining the magnetic field strength between the flyer sheet and a one-turn coil was presented. By neglecting plastic deformation of the flyer, the model allows to calculate the transient velocity and displacement behavior, too. The electromagnetic acceleration of 5000-series aluminum alloy sheets was investigated under various experimental parameters. Utilizing Photon Doppler Velocimetry revealed that the analytical model appropriately describes the influence of current amplitude, coil geometry, and, especially, discharge frequency on the velocity-displacement curve of the flyer and hence on the impact velocity. The model introduced was applied to compute the impact velocity for the welding of long lap joints of 5000-series aluminum alloy sheets and 6000-series aluminum alloy hollow profiles. Through peel tests it was shown that the weld strength at least complied with the strength of the weaker base material as failure always happened in the flyer sheet. The wavy interface pattern typical for impact welding was identified with the help of metallography.