Influence of axial workpiece position in the coil for electromagnetic pulse joining. Shed some light on the black box

Magnetic Pulse Welding (MPW) enables the fabrication of joints via the harnessing of Lorentz forces, which result from discharging a current pulse through a coil. In the process an outer piece (flyer) is accelerated onto an inner piece (parent), and welding is achieved using propagating impact fronts. The working length of the experimental setup allows for various shapes of the deformation front, and each configuration has its own advantages and drawbacks. The objective of this work is to show how the working length of tubular MPW specimens affects the front propagation as well as to indicate ways to optimize the front propagations, which are vital to the welding result. It is shown that for steel-aluminum joints, three different front regimes exist, which are related to geometrical factors. These results may be used to avoid seemingly favorable but nevertheless suboptimal conditions for flyer movement, which reduce the weld quality and the energy efficiency of the process. Additionally, the methodology presented here may allow for faster process optimization without the need for time-consuming metallographic analyses.