Vibration characteristics of a pre-twisted multi-blades-hub rotor system with blade stiffness mistuning

The hub-blade rotor structure is widely used in aero engines, gas turbines, and other rotating machinery. However, most of the existing literature regards this structure as two independent components and discusses their vibration characteristics separately, ignoring the coupling effect. In this paper, based on Donnell shell theory and Euler-Bernoulli beam theory, the energy expression of free vibration of a rotating thin-walled coupled cylindrical shell beam is derived by applying the substructure modal synthesis method. The structure's governing equation is established using the Lagrange equation and the hypothesis mode method considering the displacement continuity condition. Through a combination of the Kriging surrogate model and adaptive genetic algorithm (AGA), the stiffness detuning of the hub-blade rotor system is extensively investigated. The effects of structural parameters such as the length-to-thickness ratio and diameter ratio of the cylindrical shell, length-to-diameter ratio of the beam, installation angle, torsion angle, and installation position on the natural frequency of vibration for a coupled multi-beams cylindrical shell structure are discussed in detail. The vibration primarily induced by the blades predominantly affects low-order frequencies and exhibits sensitivity to mistuning, while the vibration primarily caused by the hub predominantly influences higher-order frequencies and remains largely unaffected by mistuning.