Electromagnetic Pulse Welding: Process Insights by High Speed Imaging and Numerical Simulation

Abstract

Most researches on the mechanisms of impact welding in general base their results on the investigation of the joint area after the process, primarily by destructive testing. A detailed analysis of the joining process itself, especially concerning electromagnetic pulse welding, has not been performed yet and thus leads to a lack of understanding. As a consequence of this, the design of the joint area and the process parameters are almost exclusively found empirically. With the help of a special image intensifier camera and a laser, which illuminates the joint area, a new attempt is made to visualize the impact in electromagnetic pulse welding. The results suggest that at least some mechanisms are currently not fully understood. Explanations are developed, mainly concerning jet formation (surface cleaning during the impact) and material behavior of the workpieces under the high strain rates of the process. Areas of large strain rates (liquid-like behavior of the metal) and areas of comparably small strain rates can be found within one workpiece. The question will be discussed whether process parameters can be gained with the help of a simulation that is sufficiently accurate at least in the macroscopic scale.