Parametric investigation of circular and elliptical bulge tests in warm hydroforming process for AA5754-O sheet

This study numerically investigated the effects of process parameter variations such as blank holder forces (800kN-1200kN), strain rates (0.00 13/sec, 0.013/sec, 0.13/sec), coefficient of friction (0.05-0.15), temperature (150°C, 260°C) and apex angles (0°, 60°, 90°, 120°) on warm hydroforming of AA 5754-O sheet blanks. Warm hydroforming process was simulated through hydraulic bulge test with circular and elliptical die openings. Dome height and sheet thinning were selected as control parameters for formability of AA 5754-O sheet blanks. Results showed that the dome height and formed blank thicknesses did not change significantly with the variation of coefficient of friction and blank holder force. Moreover, increasing forming temperature and non-isothemial conditions yielded slightly better formability. On the other hand, increase in strain rate, and elliptical type of bulge test cavity led to significant decreases in dome height and formed part thinning. Another significant finding was that the elliptical bulge test model and isothermal analyses did not reveal the effect of anisotropy for the sheet material concerned.