The formability limitation of the hole-flanging process

The incremental updated Lagrangian elasto-plastic finite-element method (FEM) was employed in this study to analyze the hole flanging of circular plates with a pre-determined smaller hole at the center of the sheet metal. An extended rmin technique was employed such that each incremental step size is determined not only by the yielding of an element Gaussian point, but also by the change in the boundary conditions along the tool–sheet interface. The frictional force in the contact region between the sheet and the tools is computed by the application of Coulomb’s friction law. Low-carbon (BA–CQ2) sheet plates were used throughout the experiments, which later were performed using a flat punch head. The experimental results were compared with FEM simulated results. It was found that using the elasto-plastic FEM can effectively predict the limitation of formability and the finished shape of the flanged holes.