Contact Damping Characteristics And Application In Rotor Dynamics

In order to come true the reliable connection of the aircraft engine and gas turbine rotor and static subsystem,the bolt connection structure is used for the reliable connection of the thin and complicated non-regular parts.The effect of bolt connection on aero engine is not only the transmission and assembly,but also reducing the dynamic response of the rotor system structure.Because the contact surface is nonlinear,it is very important to study the energy loss law of the contact surface.In this paper,the experimental research and simulation calculation of the damping aspect model of bolted joint are mainly studied.The main research contents and conclusions of this paper include:1.The cantilever beam with bolt test system is designed and built.The first four natural frequency and damping ratio of the system are tested.Test results show that: with the increase of bolt pre-tightening force,the natural frequency of each order increases,the first order damping ratio decreases,and the response amplitude of the measurement point increases.The first order contact damping ratio decreased significantly after several experiments.2.The first four order inherent characteristics of cantilever beam are obtained by means of thin layer element method,and the contact stiffness model of cantilever beam is established.The stiffness model is applied to the harmonic response of cantilever beam,and the first order common amplitude value of each node of the cantilever beam is obtained and compared with the experimental structure.Then the damping ratio of thin layer materials under different pretension forces is obtained by fitting.3.A series of cantilever beam experiments which is using the polishing washer were performed and the results are compared with the system test results using rough washers.The results show that the rough surface will increase the natural frequency of the system,decrease the damping ratio of the system and the vibration amplitude of the system.Then,the stiffness model and damping model of the smooth contact surface are established by means of the five-degree polynomial fitting method,and the comparison and analysis of the stiffness model and the damping model of the rough contact surface are made.4.The low pressure rotor system is modeled and simulated.And the contact stiffness model and contact damping model are applied to the modeling of the main nut axis of the coupling gear coupling.It is found that with the increase of the pre-tightening force of the main nut bolt,the first three order critical speed of rotor system increased slightly and the unbalanced response of the rotor system increased.5.The low pressure turbine rotor simulator is built and debugged.The inherent frequency and rotor unbalance response of rotor system under different bolt tightening torque are tested by hammer blow method.It is found that with the tightening torque of the main nut,the first order natural frequency increases,and the increase of the amplitude of the rotor response increases nonlinearly.6.The results provide a new idea for the design of bolt connection structure,assembly process design and structural dynamics analysis.