Analysis Of Global Resonance Characteristics Of Rolling Bearing And Its Dual Rotor System

The dual-rotor structures are widely used by modern aero-engines,and their inner and outer rotor are usually inter-supported by rolling bearings.The rolling bearings connect the inner and outer rotors,bringing couplings between the dynamic behaviors of these two types of rotors,which could lead complex vibrations to the whole system.Nonlinear dynamics models are mainly adopted for studying the dynamic responses of rolling bearings and their dual-rotor systems.However,some studies have pointed out that a linear simplified model can well describe the non-resonant characteristics of the system.Therefore,comparing the linear and nonlinear models,may reveal the influence of nonlinear factors on the system.This thesis will focus on the global coupling resonant characteristics of rolling bearings and their dual rotor systems.Unlike traditional method,only analyzing the trigger mechanism of a certain type of varying compliance(VC)motion in a ball bearing system,this paper will use the harmonic balance and alternating frequency/time domain(HB-AFT)method and Floquet theory to track the global VC periodic motions and their stability/bifurcation characteristics.It is found that a ball bearing system can contain multiple types of combination resonances.Due to the couplings of resonant hysteresis,dynamic stiffness and speed-frequency modulation characteristics,the VC parametric combination resonance can bring a variety of motion types such as periodic,quasi-periodic and chaotic motions to the system.Furtherly,the classic results of Fukata et al.in 1985 will also be verified by our proposed global analysis method,which can indicate the advantages of the method.The above results can help to globally classify the evolution mechanism of the complex nonlinear vibrations of rolling bearing systems.Next,the above-mentioned global analysis method is used to study the global response characteristics of a classical 4DOF inter-shaft bearing-dual rotor system systematically.By analyzing the amplitude-frequency curves and Campbell diagrams of the linear model(without considering the nonlinearity of the inter-shaft bearing),it is clear that the system has high-order resonance caused by the support stiffness of the inter-shaft bearing.Then considering the nonlinearities of the inter-shaft bearing(i.e.,bearing clearance,VC parametric excitation and Hertzian contact),it is found that the inter-shaft support nonlinear factors can make the amplitude-frequency response of the high-order resonances hysteretic hardening spring characteristics,which leads obvious bistable jumping vibration behaviors to the system.Finally,the trigger mechanism of the nonlinear resonances is analyzed,and the influences of the speed ratio,the stiffness of the inter-shaft bearing,the radial bearing clearance,and the VC excitation on the resonances are studied.This article may have certain significance for the analysis and dynamic design of the coupling dynamic characteristics of rolling bearings and their dual-rotor systems.