Increasing the range of producible geometries in open-die forging through superimposed stress states

• Applicant: Professor Dr.-Ing. Gerhard Hirt
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2014 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 256896401

Open-die forging is an incremental bulk forming process which is mainly used for the production of long and straight workpieces with a simple cross-section. The production of complex geometries by open-die forging usually requires additional manufacturing steps or can only be realized by a high amount of machining. Nevertheless, there is a certain demand for complex workpieces produced by open-die forging e.g. for aerospace applications or safety relevant parts.In other metal forming processes as for the production of curved extrusion or the process-integrated bending of tubes one approach to increase the range of producible geometries is the application of superimposed stresses in order to form the workpiece towards the intended geometry. This research project aims at the transfer of this concept to open-die forging to increase the range of producible geometries significantly.In the first funding period, the main focus was to generally prove the feasibility of the concept and analyze the technological potential. After analyzing the fundamental coherences for a single forming step, a kinematic concept for the production of curved workpieces in one forging pass was developed and successfully transferred to the open-die forging plant at the IBF. By this, it was possible to produce workpieces both from steel and aluminium with varying geometrical properties regarding the radius and workpiece angle which cannot be produced by conventional open-die forging. Additionally, the process-integrated torsion could be realized successfully.The second funding period aims at a further flexibilization of the concept regarding the achievable geometries and a detailed analysis of the process borders. For this purpose, in a first step the bending in vertical direction will be analyzed in detail, since this prevents the observed sliding of the workpiece between the forging dies and can be realized better on industrial open-die forging manipulators. A further increase of producible geometries shall be analyzed by investigating arbitrarily oriented bending direction in the 3D-space. Finally, the process borders will be analyzed in detail and concept will be evaluated, how the process can be optimized regarding these process borders for an industrial application of the concept.

• DFG Programme: Research Grants