Experimental study and finite element simulation for determining the forming window of 6063-O aluminum tube in warm hydroforming process

In recent years, aluminum and magnesium alloys have attracted the attention of researchers and engineers due to higher strength to weight ratio, compared with steels. The main limitation of these alloys is the low formability at room temperature. In order to overcome this limitation, researchers have shown that the formability of aluminum alloys increases at high temperatures. Tube hydroforming is known as a novel metal forming process in which the fluid internal pressure and the axial force are applied simultaneously to the tube. In this study, the formability of 6063 annealed aluminum tube has been investigated in warm tube hydroforming process. The effects of pressure and axial feed on the thickness distribution, bursting pressure and the respecting bulge height at different temperatures have been studied experimentally and numerically. In order to numerically predict the onset of fracture in the process, three criteria, namely equivalent plastic strain acceleration (second derivative), major strain acceleration, and thickness strain acceleration were used. Moreover, a geometrical method was adopted in the simulation to determine the wrinkling. By comparing the results, there was an acceptable accordance between experimental and simulation results. By using experimental tests and finite element simulation, the process windows of the 6063 annealed aluminum tube were obtained at the temperature of 25 °C and 250 °C. According to the process window obtained at 25 °C compared with the one obtained at 250 °C, the pressure interval in the safe zone is about twice but the axial feed interval becomes nearly half.