Computer aided die design of straight flanging using approximate numerical analysis

Prediction of springback and minimum bending radius without failure are the main issues in die design for straight flanging process. The previously developed analytical and numerical models for sheet bending were observed to be inaccurate for straight flanging with relatively small bending radii. Finite element analysis with 2D models can be used to predict springback, bendability and tool loads accurately, but the analysis can take several hours, and pre- and post-processing are even more time consuming. Alternatively, in this paper, this problem is solved using advanced bending theory, implementing the geometric details of the straight flanging process to a mathematical model and computerized numerical analysis. The proposed method predicts springback and tool loads, particularly the minimum pad force necessary to prevent pad lift by dividing the deformation zone into three segments as pure elastic deflection without contact, elastic–plastic bending without contact and elastic–plastic bending in full contact with the die shoulder. The shift in neutral radius is modeled using an iterative procedure and taking the tool pressure and local thinning into account. The results are compared with limited experimental data as well as finite element simulations.