Numerical simulation of impact welding processes with LS-DYNA

Impact welding enables metallurgical bonding even between dissimilar metals. The bond is formed during a high speed impact between the two workpieces to be joined. In the application, the accelerating force is provided by an explosive (explosion welding, EXW) or by an electromagnetic field (electromagnetic pulse welding, EMPW). One workpiece is usually accelerated within a few millimeters up to 200m/s and above. The impact and consequently the bond formation takes place in only few microseconds which makes it hard to observe. In addition to the two mentioned processes, a test rig has been built at the Institute for Production Engineering and Forming Machines which produces the impact purely mechanically. The numerical simulation with LS-DYNA will be used to gain detailed insights into the process. Three phenomena, which are thought to have a significant effect on the bond formation, are currently investigated numerically: The supersonic displacement of the surrounding gaseous medium, the strains and strain rates inside the bonding zone and the macroscopic flow of material. In addition, the process of electromagnetic pulse welding is investigated as a reference. The results of the numerical simulations will be compared to high speed images from the experiments and metallographic investigations. The comparison and fusion of the findings is used to draw new conclusions on the formation mechanisms of the bonding zone.