A Model accounting for Stiffness Weakening of Curvic Couplings under Various Loading Conditions

Curvic couplings are frequently used in aeroengine rotors. The stiffness of the curvic couplings is of guiding significance to the engineering design of aeroengine rotors as it is significantly different from that of continuous structures. In this paper, definitions and relations of the structure parameters for a curvic coupling are firstly introduced. Based on this proposed mechanical framework, a novel mechanical model accounting for the stiffness weakening under shearing, compression, bending, and torsion is developed for curvic couplings. In this model, a three-spring system, which consists of two types of springs, is adopted to describe the equivalent stiffness of a pair of meshing teeth of curvic couplings. The spring stiffness is obtained by employing the plane strain analysis of a discretized tooth with trapezoid pieces. Subsequently, the stiffness matrix of curvic couplings is deduced based on the deformation compatibility of each tooth and the force balance of the whole structure. A series of analyses of curvic couplings with various structure types are performed to demonstrate the mechanism behind the proposed model, and the results are verified against those obtained from finite element analyses. It is shown in this study that the pressure angle is the major factor affecting the stiffness of curvic couplings, while the compression stiffness and bending stiffness are more sensitive than other stiffnesses. Furthermore, the stiffness of curvic couplings is considerably smaller compared to that of continuous structures, indicating the importance of appropriate modelling of stiffness weakening in the design of aeroengine rotors.