Evaluation of the feasibility of the hole-flanging process using a multiple criteria method

Abstract

Software dedicated to simulating the hole-flanging process has been developed for the sheet metal forming profession. This software innovates by providing companies in this sector with an alternative, which is easier and less expensive than existing, more general, software. The hole-flanging process can be applied in various ways. The software uses the most known method in the profession to manufacture a flanged hole, which is based on expanding a hole with or without ironing. This study focuses on evaluating the feasibility of the hole-flanging operation. Three fracture criteria have been used for this purpose: Rice & Tracey, Latham & Cockroft and the Hole Expansion Ratio (HER). The first two criteria apply an uncoupled approach and the values of the criteria are compared with the corresponding thresholds post-process. The third criterion is used either as input data or as a test to determine thresholds for the first two criteria. The fracture thresholds are determined from experimental trials on press and from hole-flanging simulations based on the same configurations. Various hole-flanging trials with or without ironing have been carried out. Comparing the results of experimental trials and simulations highlights similar flange geometries and forming forces. The simulation shows that the locations of fracture areas on the flange are accurately modelled. However, differences appear regarding the sensitivity of the criteria to the process parameters. In particular, the fracture thresholds for the criteria may vary according to whether the flanging is carried out with clearance or with ironing. For this reason, the software allows the user to view the two criteria and choose the best one for their configuration. The HER test is used to determine thresholds for the fracture criteria and seems to be suitable for subsequently evaluating the feasibility of new flanging configurations.