Methodology for the design of recursively axially formed rotor shafts made of two or more combined segments

Electric drives are used in all industrial fields in a growing number. Whereas the rotor shafts used in the area of machinery and plant engineering are designed as solids, the shafts mainly used in the field of automotive industry are hollow shafts focusing on the lightweight potential and the improvement of motor characteristics. This paper describes a shaft design consisting of two or more segments manufactured by a new combination of certain cold forming processes before joining. This design enables higher flexibility of variants as well as optimization of production efficiency and logistic chains. Thus, the joint zone design is a specials erration with a helix angle in order to reach a high robustness of the shaft. A detailed FEM simulation of the elastoplastic behavior of the joint zone and the mechanical characteristics of the complete shaft leads to an evaluation of possible applications of this joint geometry and the corresponding manufacturing process. Based on experimental investigations, the simulations have been validated successfully. An empirical model designed by regression analysis of further simulation results is used to propose a design methodology for the identification of design parameters of the assembled shaft and the joint zone as well. These parameters can be used for planning the forming processes and the blank geometry.