Dynamic Analysis of Geared Rotor System with Hybrid Uncertainties

Current research on the dynamics and vibrations of geared rotor systems primarily focuses on deterministic models.However,uncertainties inevitably exist in the gear system,which cause uncertainties in system parameters and subsequently influence the accurate evaluation of system dynamic behavior.In this study,a dynamic model of a geared rotor system with mixed parameters and model uncertainties is proposed.Initially,the dynamic model of the geared rotor-bearing system with deterministic parameters is established using a finite element method.Subsequently,a nonparametric method is introduced to model the hybrid uncertainties in the dynamic model.Deviation coefficients and dispersion parameters are used to reflect the levels of parameter and model uncertainty.For example,the study evaluates the effects of uncertain bearing and mesh stiffness on the vibration responses of a geared rotor system.The results demonstrate that the influence of uncertainty varies among different model types.Model uncertainties have a more significant than parametric uncertainties,whereas hybrid uncertainties increase the nonlinearities and complexities of the system’s dynamic responses.These findings provide valuable insights into understanding the dynamic behavior of geared system with hybrid uncertainties.

Detection of asymmetric transmission error in geared rotor system through transverse vibration analysis using full spectrum

Transmission error(TE)in geared rotors is a predominant source of inherent excitation at the pitch point of the gear meshing.In this paper,a transverse vibration analysis is presented to study the effect of TE on geared rotors.Due to asymmetry in the TE,it is expected to have both forward and backward whirls excited during rotor whirling,which could be used for its detection.This aspect has been envisioned first time in the present work.To capture this,an approach of orienting the line of action of a gear-pair along oblique plane is considered and the mathematical modeling has been performed of a simple spur gear-pair connecting two parallel shafts at its mid-span with an asymmetric TE.To capture the forward and backward whirls,equations of motion are converted into a complex form that facilitates obtaining response in full spectrum.The response of system model with assumed transmission error and gear-pair parameters has been obtained through a numerical simulation,which shows distinctly the forward and backward whirls due to the TE.Through a simple test rig experimentation,a similar behaviour was observed in transverse vibrations of geared rotors in the full spectrum,which validate the proposed model.

High cycle fatigue failure with radial cracks in gears of aero-engines

The gears in aero-engines perform energy and motion transfer between the HighPressure Rotor(HPR)and accessories.Firstly,an occurred fault with radial cracks in the driven gear disk was diagnosed as High Cycle Fatigue(HCF)failure through necessary examinations.Analysis of fault tree and test signals indicated that the fracture was relevant to the swing vibration of the driven gear excited by the unbalance excitation on HPR.Secondly,a corresponding mechanism model was established,in which the gear meshing effect was considered,with lateral and swing vibration mode.The Governing Equations(GEs)and the Finite Element Model(FEM)were established and verified.Then,the modal shapes,harmonic response,and transient response were analyzed,indicating that the swing vibration of the driven gear could be significantly excited by the unbalance on HPR,which induced the cracks in the driven gear disk to extend radially.Furthermore,influences of factors on the unbalance response were obtained,in which the unbalance response appeared local minimum points and maximum points.Meanwhile,1#and 2#bearing stiffness had rather significant influences on the response.Thus it is efficient to modify them to achieve vibration control.