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A common occurrence in computer aided design is the need to make changes to an existing CAD model to compensate for shape changes which occur during a manufacturing process. For instance, finite element analysis of die forming or die tryout results may indicate that a stamped panel springs back after the press line operation so that the final shape is different from nominal shape. Springback may be corrected by redesigning the die face so that the stamped panel springs back to the nominal shape. When done manually, this redesign process is often time consuming and expensive. This article presents a computer program, FESHAPE, that reshapes the CAD or finite element mesh models automatically. The method is based on the technique of volume morphing pioneered by Sederberg and Parry [Sederberg 1986] and refined in [Sarraga 2004]. Volume morphing reshapes regions of surfaces or meshes by reshaping volumes containing those regions.

A demonstration of the preform anneal process was conducted to form a one-piece aluminum door inner. In preform annealing, the aluminum panel is partially formed, annealed at 350°C to eliminate the cold work (strain hardening) 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. Preform annealing uses non-age hardenable aluminum alloys of the 5xxx series and is suitable for a wide range of interior body panels. A rear door inner panel for a mid-size sports utility vehicle (SUV) was used in this study. This door inner was successfully created in one piece out of AA5182-O sheet with only slight design modifications to the original steel product geometry. The design of the door inner panel was conducted based on finite element analysis and predictions were verified with physical parts using thickness measurements and mechanical testing.