Analysis Of Dynamic Characteristics Of Rotor System With Bolted Joints

Joints are often needed in rotor system while the bolted joints are widely used as a common connection structure.When rotor system running at high speed,the bolt joint will be affected by external force due to the change of complex load,cause the preload of bolts decrease.At present,the research of bolted joint in rotor system mainly focus on bolt loosening at stationary parts or consider the influence of bolted joint in rotor system under normal tighten state.However,bolt loosening behavior always exists in rotor system.Therefore,based on the bolted joint of the low-pressure rotor system of aero-engine,the finite element model was established by Ansys.Then analyzed the bolts preload determined the position of bolt loosening.Next,calculated the time-varying stiffness caused by bolts loosening and investigated it variant impact by the bolts loosening number and pre-tightening force.Then,the dynamic equation of the rotor system with bolted joint was established,and investigate the dynamic characteristic of rotor system.The research contents of this paper include:(1)A single bolt is as the research object,focus on its physical model,from the aspect of calculation accuracy and time to analysis the finite element modeling.Specificly,analyze the characteristics of different finite element modeling methods,and then choose a appropriate modeling method for next analysis.(2)Taking the simplified model of the bolted joint in aero-engine low-pressure compressor as the research object,established the finite element model.Based on the working environment and the actual load situation of the low-pressure compressor,analyze the preload of each bolt under the bending moment,torque and coupling load,so as to determine the bolt loosening position.(3)Based on the LMS test system in the laboratory,analyze the inherent characteristics of the drum bolt structure in different bolt pretightening force and bolt loosening number.In addition,analyze the natural frequency of the drum bolt structure in different bolt preloading force and bolt loosening number.(4)Establish the equation of bolted rotor system considering bolt loosening.Specifically,the disk,the rotating shaft and the bolted joint are modeled respectively,and then introduced the bolt time-varying stiffness.Finally,analyze the dynamic characteristics of the rotor system with bolt loosening.In addition,the rotor system under bolt loosening state was compared with that under normal tightening state,and the difference was used to monitor bolt loosening.