Influence of the punch profile on the limitation of formability in the hole-flanging process

This paper applies the incremental updated Lagrangian formulation of the elasto-plastic finite element computer code 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 the size of each incremental step is determined not only by the yielding of an element Gaussian point but also by the change in the boundary conditions along the tool interface. Coulomb’s friction law was adopted to solve the frictional effect of the tool–metal interface. The metal was low-carbon (BA–CO2) sheet plates with a thickness of 1.18 mm. This work aims to investigate the influence of the cylindrical punch profile radii on the limitation of formability in the hole-flanging process. The experimental results were compared with the FEM-simulated results. It was found that the limitation of formability during the hole-flanging process is not affected by the punch profile but that the finished shape and maximum punch load are dependent on the punch profile.