Sheet-Metal Formability Study on a Circular Tube with a Folding Bottom Feature

The formability of sheet-metal with a folding-bottom circular hollow tube has been studied both by numerical simulation and experiment. A mesh-convergence analysis has been carried out to determine an optimum element size for purposes of numerical simulation. The geometry and dimension of the dies and of the punch are designed to simulate the multi-stage deep drawing operation to take place. During the deep drawing operation, the strains of the sheet blank are always located in the second quadrant of the forming limit diagrams, and it continuously moves in a linear state to the left side of the diagram. At the final stage, the tube is drawn to a certain height without evidence of fracture. In order to obtain a quality product, an optimization of input parameters for the deep drawing operation is conducted using Taguchi method. Finally, a validation test is also employed to demonstrate the accuracy of forming processes. The result reveals sufficient agreement in both geometry and dimension between simulated and actual tubes to meet a good quality standard.