Modeling and characteristics of aero-engine rotor with bolted-rabbet joints

Abstract:

To address the challenge of characterizing the dynamic properties of bolted-rabbet joint structures in aero-engine rotors under high rotational speeds and multi-load excitation, a rotor dynamic modeling method considering multiple bolted-rabbet joints is established, and the influence of joint interfaces on the rotor’s natural characteristics, critical speeds, and unbalance response is systematically revealed in this study. Firstly, SOLID186 solid elements are employed to model the disks and shafts, COMBI214 elements to simulate the bearings, and MATRIX27 elements to characterize the multi-dimensional stiffness (tensile, lateral, bending, and torsional) of the joint interfaces. By combining the MPC (multi-point constraint) contact algorithm to achieve degree-of-freedom coupling with the bolted-rabbet assembly surfaces, a high-precision dynamic model is established for aero-engine rotors with bolted-rabbet joints. Secondly, a rotor test rig with multiple bolted-rabbet joints is constructed. Ultrasonic preload testing, modal testing, and excitation experiments are conducted to acquire bolt preloads, natural characteristics under different boundaries, and vibration responses under constant-frequency and sweep-frequency excitation, thus verifying the model’s correctness. Finally, the influence of bolted-rabbet joints on the rotor system’s critical speeds and unbalance response is analyzed. The results show that: the bolted-rabbet joint interfaces significantly affect the rotor’s free modes, and ignoring interface stiffness results in the overestimation of natural frequencies; under bearing support, the joint interfaces have minimal impact on translational and pitching modes but a pronounced influence on bending modes, and notably alter the critical speeds associated with bending modes; in the unbalance response, the amplitude of bending modes increases significantly due to interface stiffness loss, and discontinuities in lateral and rotational displacements emerge in the speed interval between the 2nd and 3rd critical speeds. This study provides theoretical support for the design optimization of joint structures in aero-engine rotors.