Formability Evaluation of 3D Closed Section Parts from Sheet Metal Based on Geometrical Information

For successful sheet metal forming, a complex design and trial process are inevitably necessary. That complex process is geometrical design, forming process selection, tool / die face design and forming condition. It may take couple of months to carry out this process, and at the end of this process try out may result in unsuccessful. The cause of this unsuccessful try out is difficult to find out because of the complexity of the design and try out process. It is proposed that a new evaluation methodology can provide semi-quantitate evaluation for the forming difficulty of the sheet. The proposed method evaluates only geometry of sheet metal parts, starting with Riemann curvature, which is decomposed into Gaussian curvature and metric tensor. Because the nature of sheet metal forming failure (breakage and wrinkle) are mainly related to in-plane deformation and not so much related to out of plane bending. Gaussian curvature is an excellent index for in-plane deformation caused by geometry angulation. Metric tensor provide quantitative evaluation for in-plane deformation. Computational time for this proposed method is a couple of minutes and is suitable for the evaluation and modification of the upstream design.