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

开式模锻是一种增量体积成形工艺，主要用于生产具有简单横截面的长直工件。通过开式模锻生产复杂的几何形状通常需要额外的制造步骤，或者只能通过大量的机加工来实现。然而，对于通过开式模锻生产的复杂工件，例如用于航空航天应用或安全相关部件，存在一定的需求。在其他金属成形工艺中，例如用于生产弯曲挤压件或管的工艺集成弯曲件，一种增加可生产几何形状范围的方法是施加叠加应力，以便使工件朝向预期几何形状成形。该研究项目旨在将这一概念转移到开式模锻中，以显著增加可生产的几何形状范围。在第一个资助期内，主要重点是全面证明这一概念的可行性，并分析技术潜力。在分析了单个成形步骤的基本连贯性之后，开发了一种在一个锻造道次中生产曲面工件的运动学概念，并成功地转移到IBF的开式模锻工厂。通过这种方式，可以由钢和铝生产工件，这些工件具有关于半径和工件角度的变化的几何特性，这是传统的开式模锻无法生产的。第二个供资期的目的是进一步灵活化关于可实现几何形状的概念，并详细分析工艺边界。为此，在第一步中，将详细分析垂直方向上的弯曲，因为这防止了观察到的工件在锻模之间的滑动，并且可以在工业开式模锻操作机上更好地实现。应通过研究3D空间中任意取向的弯曲方向来分析可生产几何形状的进一步增加。最后，将详细分析过程边界，并对概念进行评估，如何针对这些过程边界优化过程，以实现概念的工业应用。

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.