Analytical design and experimental validation of uniform pressure actuator for electromagnetic forming and welding

In this paper, an analytical model is used to design a coil, called a Uniform Pressure Actuator (UPA), for use during electromagnetic forming (EMF) and magnetic pulsed welding (MPW) by combining and extending past efforts by other researchers. The UPA offers increased forming efficiency and repeatability, as well as a robust design. Magnetic pressure applied to the workpiece and workpiece velocity are predicted to ensure impact conditions are sufficient for MPW. The UPA is constructed and tested experimentally to validate the accuracy of the analytical model, as well as verify assumptions made during modeling. The coupling coefficient introduced in the magnetic analysis is experimentally determined and compared to previous researchers' values. Workpiece velocities for various energy levels, workpiece thicknesses, and materials with various conductivities and densities are compared to analytical predictions and show good agreement for the initial acceleration in the process. Workpiece velocity measurements were obtained using a Photon Doppler Velocimetry (PDV) system, which provides a robust method for measuring velocities with submicron displacement and temporal resolution in the nanosecond range. Uniformity of the workpiece deformation is also examined, which is an advantage of the UPA.