Pressure-assisted forming of non-concentric tubular cross sections with solid medium

Pressure-assisted forming of tubes allows producing a wide variety of tubular components that are difficult or impossible to fabricate by means of conventional tube forming. In contrast to previous investigations in the field that were almost exclusively focused on the utilization of fluids (tube hydroforming) or elastomers (tube rubber forming) as pressuring medium, the subject matter of this article is centred in the utilization of low melting point, recyclable, metallic alloys as solid pressurizing medium. The aims and scope of the article are centred on the feasibility of forming straight carbon steel tubes into complex gooseneck geometries with non-concentric cross sections using lead as a solid pressuring medium and employing a double-action cam-driven tool system. The presentation is focused on the tool system, on its adequacy to produce customized tubular components, on the required forming forces and on the typical modes of deformation that result from the different movements provided by the vertical and horizontal actuators of the double-action tool system. Results and observations confirm that the utilization of a double-action tool system with a solid pressurizing medium to assist plastic deformation and prevent collapse can be successfully and effectively employed to fabricate non-concentric tubular cross sections for prototypes and small batches of lightweight components.