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

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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.