Influence mechanism of disk position and flexibility on natural frequencies and critical speeds of a shaft-disk-blade unit

The present study intends to investigate the influence of the disk's position and flexibility on the critical speeds (CSs) and natural frequencies (NFs) of a coupling shaft-disk-blade unit. To this end, an improved shaft-disk-blade coupling model is proposed. In the developed model, swing motion of the flexible bladed disk structure originating from the shaft bending is considered. Moreover, the gyroscopic moment due to the disk flexibility is considered in the derived model. The blade is modeled as an elastic support Timoshenko beam, while the corresponding mode function is derived and validated. Performed analyses show that the proposed model is more accurate than conventional models. Obtained results from the numerical simulation indicate that the disk position (η) and disk flexibility (ξ) have a significant impact on the NFs and CSs. Moreover, η and ξ play a significant role in the aggravating and mitigating of the coupling characteristics. Campbell diagrams are also illustrated to interpret the change rules of the CSs against η and ξ. In the Campbell diagram, some loci intersection phenomena appear, which shift significantly due to the variation of η and ξ. Obtained results suggest that a wide range of these parameters should be analyzed to present a more detailed coupling mechanism among the subcomponents.