COMPARISON OF FREE AND RESTRAINED BULGE FORMING BY FINITE-ELEMENT METHOD SIMULATION

Most finite element analysis of bulge forming or more specifically bul ge testing were done for possible simplest cases. These analyses used pressure as forming load holding the periphery fixed thus involving no contact phenomenon. In real forming cases contact is an essential fea ture and involves pushing of material into the bulge. Ahmed and Hashmi [4] simulated bulge forming of a circular plate applying pressure on p late surface and inward displacement of the plate periphery in a die c onfiguration. It was observed that the bulge formed by the combined lo ad is higher, has more uniform thickness and has less stress and strai n. It is expected that if the bulge is restrained at the polar region rather than allowed to form free, it might result in a bulge with long er cylindrical part which is more desirable from manufacturing point o f view. This paper presents the results of simulation of bulge forming by combined load with and without a restraining load and without one. It is found that the bulge formed with a restraining load not only ha s longer cylindrical part but also has higher bulge height than in tha t obtained without a restraining load at the polar region. However, th e restrained bulge developed more stress and strain but their distribu tion in the bulge are relatively smoother.