Electromagnetic expansion joining between tubular and flat sheet component

Abstract

Abstract To join tubular and flat sheet components, this paper investigates an electromagnetic expansion joining (EMEJ) method, which combines tube expansion and electromagnetic forming (an emerging high-speed forming technique). To enable partial modification of the conductive coil, an assembly-type Bitter coil was utilized. The aluminum alloys AA6063-O and AA7075-T6 were selected for the tube and flat sheet joining targets, respectively. EMEJ tests were performed with several charging voltages: 5.7, 7.5, 9.2, and 11.1\u2009kV. Three EMEJ mechanisms were revealed by numerical simulations: a geometrical constraint imposed by the bulging and flanging of the tube, an interference fit imposed by the residual stress, and an indenting phenomenon caused by impact with the flat sheet. Complete joining without any looseness was accomplished at charging voltages of 9.2 and 11.1\u2009kV. Through pull-out testing, the connection strength was confirmed to be higher than the yield strength of the tube, as was predicted by the numerical simulation. As a result, the tube and flat sheet were successfully joined by EMEJ without additional connecting elements, and the feasibility of EMEJ as an advanced joining technique was verified.