An investigation of creep age forming of AA7B04 stiffened plates: Experiment and FE modelling

Creep age forming (CAF) of aluminium alloy 7B04 (AA7B04) stiffened plates has been experimentally and numerically investigated in this study. Creep-ageing experiments of AA7B04-T651 were conducted under different tensile stress levels at 140 degrees C for up to 20 h, and a set of unified constitutive equations was calibrated based on the experimental results of the evolutions of creep strain, yield strength and precipitate size, which was implemented into ABAQUS for CAF process modelling. CAF experiments and corresponding simulations of AA7B04 stiffened plates were then carried out and the effect of stiffener height and die radius on springback and yield strength was studied. It was found that the springback percentage decreases with increasing stiffener height and decreasing forming die radius, and the yield strength is slightly lower in the stiffener than in the skin of the CAFed stiffened plates due to stress effect on ageing progression. A good agreement has been achieved between experimental and corresponding FE results, with maximum deviations of 6.7% and 3.3% respectively for springback and yield strength.