Dynamic modeling and natural characteristic analysis of discontinuous rotor systems with multiple joint structures

Bolts, splines, and spigot joints are typical joint structures widely employed in the disk-drum combined rotor systems of aero-engines. In existing research on the dynamic characteristics of such systems, components such as spigot joints and splines are often modeled as integrated parts, so the influences of the joint interfaces on the rotor's dynamic behavior are neglected. To address this limitation, a refined dynamic model that incorporates joint structures is developed to investigate the effect of joint stiffness on the modal characteristics of disk-drum rotor systems. First, the stiffness of bolts, splines, and spigot joints is calculated and then the joint stiffness is incorporated into the finite element (FE) model of a rotor system using a beam-shell hybrid element approach. The results indicate that the variation in rotational speed induces complex mode coupling and frequency veering (FV) phenomena in the rotor system, including mode shape interaction and multiple veering points across different traveling wave modes. Furthermore, the axial and transverse stiffness of typical joint structures significantly affects the natural frequencies of the system with threshold effects. These findings highlight the multi-level and variable nature of frequency veering in response to changes in joint parameters.