286 Modern Metalworking Copyright Goodheart-Willcox Co., Inc. PA&E Bonded Metals Division, Sequim, WA Figure 17-23. This skin for a space shuttle engine was made as one part with explosive forming. A—The preform is created in the general form of the finished piece and placed in the die. B—The explosion forces the preform to take on the shape and details of the die. A B Electrohydraulic Forming When electrical energy is used to produce the energy pulse, the process is known as electrohydraulic forming. In this process, a surge of electrical energy provides the pressure pulse in much the same man- ner as a chemical explosive, Figure 17-24. The elec- trical energy is stored in capacitor banks. The con- trolled discharge of the electrical energy across a gap between two electrodes or across an explod- ing bridge wire submerged in the water produces a high-energy shock wave. The wave radiates out from the electrodes and forces the work against the die face. Magnetic Forming Electromagnetic forming, also known as g g magnetic pulse forming, uses an insulated induction coil either g g wrapped around or placed within the work. The loca- tion of the coil depends on whether the metal is to be squeezed inward or bulged outward. See Figures 17-25 through 17-27. The coil is shaped to produce the 7 7 required contours in the workpiece. NASA Figure 17-24. Electrohydraulic forming uses electrical energy as a source of power for HERF operations. Vacuum line Initiation wire (optional) Electrodes Water Hold-down bolts Premachined blank Tank cover Electrode terminations Hoist Switch Power supply Capacitor bank Die Vacuum seal