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It is important to understand the accuracy level of the formability analysis for any new process so that correct predictions can be made in product and die design. This report focuses on the formability analysis methodology developed for the preform anneal process. In this process, the aluminum panel is partially formed, annealed to eliminate the cold work from the first step, and then formed to the final shape using the same die. This process has the ability to form more complex parts than conventional aluminum stamping, and has been demonstrated on a complex one-piece door inner and a complex one-piece liftgate inner with AA5182-O3. Both panels only required slight design modifications to the original steel product geometry. This report focuses on the formability analysis correlation with physical panels for the liftgate inner, considering both full panel anneal in a convection oven and local annealing of critical areas.

Dual phase steels are becoming increasingly popular choices for automotive structural applications at General Motors (GM) due to their strength and relatively good formability. Coming with it is the challenge for the manufacturing processes to produce the desired product with consistency. At GM, math-based die engineering process has been a reliable tool for tube hydroforming formability with conventional steels. This paper presents a validation of this math-based process for bending and hydroforming dual phase steel tubes. Several grades of dual phase steel tubes and conventional mild steel tubes are used to hydroform an experimental part. Final part thickness, and dimensional springback are measured and compared with simulation predictions. The results demonstrate the validity of this math-based process for formability of dual phase steel tubes and the ability to predict springback directions and magnitude estimation.