An enhanced design method for 3D contact surfaces on shaft–hub connections joined through lateral extrusion

Abstract

A recently developed design method for circular shaft–hub connections joined using the cold-forming process of lateral extrusion allows predefined contact stress distributions to be generated on the contact surface by gradient-less shape optimization. Using contact stress results from elastic-plastic finite-element analyses and simplified rules derived from cylindrical interference fits, the contact surface of the hub is adapted locally to the shape of the formed shaft in an iterative process. In this paper, the design method is expanded from circular to non-circular profile shapes based on complex cycloids to create optimized, polygon shaft–hub connections, minimizing sliding and fretting fatigue under dynamic loads. To enable local adaptation of non-circular contact surfaces, we introduce a suitable definition for 3D profiles, which allows simultaneous variation of the profile mean radius and eccentricity. This allows designers to create contact surface designs with complex shapes that conform to predefined contact stress distributions along the connection length. The feasibility of the method is finally demonstrated by undertaking a design adaptation study on a sample non-circular shaft–hub connection and comparing the results to the initial design. While the contact stress results for the adapted design agree very well with the specified target curves, an overall more uniform stress distribution in the hub is also achieved. Due to its combined form and friction-fit properties with high residual contact pressure, the connection is predestined for use in novel electric and hybrid drive applications, where lightweight design as well as high power density and rotational speeds are required.