| Superplastic Forming (SPF) is a process used to form a certain type of materials, called superplastic materials, into complex components. These materials can, under certain conditions, undergo extraordinary large ductility. The SPF process has many unique advantages over conventional forming operations including significant cost and weight savings potentials. Quick Plastic Forming (QPF) is a derivative of SPF, developed by General Motors Corporation, which offers comparable capabilities to SPF, yet at higher production rates. In order for the SPF and QPF processes to become acceptable as efficient high rate production forming processes, their outputs should be accurately predictable and the forming times must be reduced without compromising the integrity of the formed parts.;Up to this point, only a few simulations of the superplastic forming process that have been conducted consider both accurate material models and sophisticated numerical tools. In addition, the forming gas pressure profiles applied in production are primarily based upon a trial-and-error approach. Prediction of gas pressure profiles that reduce SPF/QPF cycle times below what they are with the current profiles but without increasing thinning has not been extensively explored with FE simulations. Analytical stability criteria from sheet metal failure theories have been used to design deformation paths. However, there is not yet a universal procedure for designing variable strain rate deformation paths. The difficulty comes from the lack of accurate constitutive models for superplastic materials and the complexity of predicting failure in them.;An accurate material constitutive model for the SPF grade of the aluminum alloy AA5083 was developed and successfully used in simulating high-temperature bulge forming and the QPF of the license plate pocket portion of the Oldsmobile Aurora decklid. In addition, the effect of different procedures for gas pressure application and changing the friction conditions across the die-sheet interface on the predicted forming time and product quality was investigated.;Finally, a procedure for designing strain rate deformation paths was developed and its results were compared with those derived from available stability theories.;KEYWORDS: Superplastic Forming, Quick Plastic Forming, AA5083, Finite Element Modeling, Stability Analysis. |
