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

This paper applies the incremental updated Lagarngian formulation of the el asto-plastic finite element computer code to analyze the hole-hanging of ci rcular plates with a pre-determined smaller hole at the center of the sheet metal. An extended r(mm) technique was employed such that the size of each incremental step is determined not only by the yielding of an element Gaus sian point but also by the change in the boundary conditions along the tool interface. Coulomb's friction law was adopted to solve the frictional effe ct of the tool-metal interface. The metal was low-carbon (BA-CO2) sheet pla tes with a thickness of 1.18 mm. This work aims to investigate the influenc e of the cylindrical punch profile radii on the limitation of formability i n the hole-flanging process. The experimental results were compared with th e FEM-simulated results. It was found that the Limitation of formability du ring the hole-hanging process is not affected by the punch profile but that the finished shape and maximum punch load are dependent on the punch profi le. (C) 2001 Elsevier Science B.V. All rights reserved.