Finite Element Simulation of Springback in Sheet Metal Forming

Springback during unloading affects the dimensional accuracy of sheet metal parts. A finite element model is proposed to predict springback with contact evolution between the sheet and dies based on U-bending benchmark of Numisheet 1993. The underlying formulation is based on updated Lagrangian elastoplastic materials model. BHF is modeled as an effective force on the edge of the flange. Sheet unloading is simulated by the tools' reverse motion. Sensitivity analysis done using the finite element method (FEM) demonstrated that the magnitude of springback and the overall accuracy are highly influenced by the element size, integration points and yield criteria. The solutions validated with experimental data of Numisheet 1993 show more accurately than 90%. The optimal model derived from FEM analysis provides an accurate solution and small convergence. It also has merit in not requiring excessive computation time.