转 轴 -轮 盘 -裂 纹 叶 片 耦 合 系 统 的 叶 尖 振 动 特 性

Aero-engine blades，subjected to extreme environmental conditions，are susceptible to crack develop⁃ ment，which shortens blade life and seriously affects the safe operation of aero-engine. This paper focuses on the shaft-disk-cracked-blade coupling system which is modeled using the mixed strategy of the finite element method and the assumed mode method. The shaft is simulated by finite element method，while the disk and blade are simulated by Kirchhoff plate theory and Timoshenko beam theory. A dynamic model is built based on time-varying loss stiffness caused by the breathing crack which is determined by the time-varying release strain energy. The correctness of the proposed method is confirmed by comparing the natural characteristics and vibration responses of the coupling sys⁃ tem. The influences of gravity load，rotor unbalance force and aerodynamic load on vibration characteristics of the blade tip are analyzed，and the impact of different dimensionless crack depths and crack locations on the vibration characteristics of the blade tip are investigated. The research results show that：in a healthy blade，the gravity load can cause the blade to vibrate，and the unbalanced force can induce the static deformation of the blade；under rota⁃ tion，the cracked blade leads to the bending displacement of the blade tip，which produces an offset，while under the action of aerodynamic load，the breathing crack results in nonlinear vibration of the blade；the amplitude ratio of the constant component to the rotational frequency and the amplitude ratio of the constant component to the aerodynamic excitation frequency are valuable indicators for assessing breathing crack. The modeling method and analysis conclu⁃ sions in this paper can provide a specific theoretical basis for the fault diagnosis of aero-engine blade crack.