Damping analysis method for cyclic structure with shroud and blade/disk interfaces

The low-pressure turbine is a critical component of turbine engines, where the shroud and blade/disk interfaces contribute significantly to damping. However, analyzing the nonlinear characteristics and damping effects of these interfaces remains challenging. In this study, a finite element model for a single sector of a bladed disk is modeled. To enhance computational efficiency for this cyclic symmetric structure, a reduced-order modeling approach by combining cyclic boundary conditions with the Craig-Bampton method is proposed. The nonlinear vibration patterns are calculated, which includes the damping ratio, resonant frequency and displacement distribution under different amplitudes. The contact angle of the shroud is optimized to improve damping ability. The vibrational stress is calculated to relate the result of displacement with the issue of high cycle fatigue. The displacement of non-contact surfaces on the shroud is extracted using the vibrational stress to decide its clearance to prevent dislocation during operation. Based on the nonlinear vibration patterns obtained, our analysis reveals that the shroud interface can provide a damping ratio of up to 10%, and the damping of blade/disk interfaces is not negligible under high vibrational stress. The results show significant variations in displacement distribution and contact behavior, indicating obvious nonlinear characteristics of the structure. This study provides a practical methodology for designing shrouded blade structures with enhanced damping characteristics and preventing shroud dislocation. The proposed approach enables efficient nonlinear analysis, offering valuable insights for industrial applications in turbine engine design.