Finite element analysis and experimental confirmation of warm hydroforming process for aluminum alloy

The hydroformability of an extruded aluminum alloy at elevated temperatures was investigated in this study. To properly analyze the process, it is necessary to account for the variation in the mechanical properties of the aluminum that depend on the forming temperature and the heat conduction during warm hydroforming. Simulations coupling the plastic deformation and temperature distribution in the warm hydroforming process were performed and compared with experimental data. The multi-purpose finite element code DEFORM-2D can handle the calculations, but requires significant computation time if contact heat transfer between the die, the tube, and the pressure medium occurs. Experiments were conducted with a high temperature tribometer (pin-on-disk) allowing the measurement of the friction coefficient for the aluminum alloys at several temperatures. These friction results are applied to the coupled simulation. From the simulations, the optimal process parameters, such as internal pressure and preset temperature on hydroformability, can be found. The comparison of the finite element analysis with the experimental results shows that the hydroformability trends (given by bulge height) and the temperature distribution of the tube specimen agree well with one another. The finite element results also showed that the temperature distribution did not strongly affect the hydroformability of the aluminum tubes.