Implementation of backward tracing scheme of the FEM to blank design in sheet metal forming

Blank design is a critical part for net-shape sheet forming. This study applies the backward tracing scheme of the rigid–plastic finite element method to the three-dimensional blank design of sheet metal forming. Originally, the backward tracing scheme was developed for preform design in bulk forming, and applied to several forming processes successfully. Its key concept is to trace backward from the final desirable configuration to an intermediate preform or initial blank. A program for initial blank design in sheet forming which contains the capabilities of forward loading simulation and backward tracing simulation has been developed and proven in effectiveness by applying it to a square cup stamping process. In the blank design of square cup stamping, the backward tracing program can produce an appropriate blank configuration which forms a sound net-shape cup product without requiring machining after forming. The blank design has been confirmed by a series of experiments, since the application of the backward tracing scheme was the first trial in the blank design of sheet metal forming.