Development of 3D joining surface geometries for shaft hub connections manufactured by lateral extrusion

用于工程应用的摩擦或形式锁定轴-毂连接通常由成品部件创建。然而，简单的装配过程需要间隙，这通常会对连接造成有害影响。例如，冷连接受到操作间隙的影响，在交变载荷下会受到微动腐蚀和过早失效的影响。另一方面，热连接涉及到已经硬化的部件再回火的风险。最近的发展揭示了通过塑性变形创建轴-毂连接而没有上述缺点的可能性。例如，内部高压装配已经在汽车制造中实现了不同的部件，但这种工艺只适用于相对薄且均匀的空心轴。然而，IFU和项目合作伙伴IKTD的初步研究表明，通过横向挤压连接多层阶梯轴是可行的。在随后的研究中，这种连接的传输能力也取得了令人鼓舞的结果。因此，冷连接同时产生维持关节压力的可能性是特别有利的。此外，由于轴在初始状态下保持未加工，因此不再需要严格的连接几何公差。然而，在接触面几何形状的设计中没有考虑由于侧向挤压过程而产生的凸轴几何形状是不利的。因此，在连接处产生了不均匀的充型和连接压力分布，导致循环载荷下的微动增加。在提出的项目中，将以一种全新的方法在接触面几何的精细设计中考虑连接过程中被忽视的影响。通过引入内轮毂几何的三维设计，实现了完整的成形和控制接头压力的调整。因此，微动可以最小化，并且可以利用现有的进一步增加静态和动态传输能力的潜力。通过在包括塑性变形模拟和结构模拟在内的耦合模拟方法中对材料特性的全面考虑，将开发一个考虑几何、材料、工艺和应用要求的通用几何设计模型，从而在广泛的应用领域中有效。

Frictional or form locking shaft-hub-connections for engineering applications are usually created by finished components. However, a straightforward assembly process requires clearance, which often causes harmful effects on the connection. For instance, cold joined connections are subject to operating clearance and suffer from fretting corrosion and premature failure under alternating loads. Warm joined connections on the other hand involve the risk of retempering already hardened components. Recent developments reveal possibilities of creating shaft-hub-connections by plastic deformation without the mentioned disadvantages. As an example, internal high pressure assembly is already implemented for different components in car manufacturing, but this process is only practicable for relatively thin and uniform hollow shafts. However, preliminary studies by IFU and project partner IKTD showed the feasibility of joining multiply stepped shafts by lateral extrusion. Promising results for the transmission capability of such connections were also achieved during following studies. Hereby, the possibility of cold joining with the simultaneous creation of a maintaining joint pressure is especially advantageous. In addition, close tolerances for the connection geometry are no longer needed, as the shaft remains unmachined in the initial state. However, it is disadvantageous that the convex shaft geometry, as a result of the lateral extrusion process, is not considered in the design of the contact surface geometry. Hence, inhomogeneous mold filling and joint pressure distribution are generated in the connection, which lead to increased fretting under cycling loads. In the proposed project the disregarded effects of the joining process will be considered in the fine design of the contact surface geometry with a fundamentally new approach. By introducing a three-dimensional design of the inner hub geometry, complete form-filling and controlled joint pressure modification are pursued for the connection. Hence, fretting can be minimized and the existing potentials for further increase of static and dynamical transmission capabilities can be exploited. Via thorough consideration of material properties in a coupled simulation methodology, including plastic deformation simulation and structural simulation, a universal model for geometry design is to be developed, which takes into account geometry, material, process and application requirements and is thus valid in an extensive field of application.