# Dynamic characteristics of aeroengine center bevel gear

The research work is carried out on the bevel gear fault of an aeroengine under research. The current situation of gear dynamics research is summarized. Based on the basic theory of gear transmission system dynamics and traveling wave resonance theory, the central bevel gear transmission system of an aeroengine is studied and analyzed. The main research results are as follows:

(1) The natural characteristics of the central bevel gear of an aeroengine are calculated and analyzed by using the finite element method, and the suitable constraint conditions for the vibration calculation of the aeroengine bevel gear are determined. It is found that the higher the vibration order and the higher the pitch diameter, the less sensitive the natural characteristics of aeroengine central bevel gear to boundary constraints. It can be seen from the vibration stress distribution diagram that the vibration stress is mainly concentrated at the root of the gear tooth. Once resonance occurs, it is very easy to produce cracks from the root of the tooth. The traveling wave analysis of this type of aeroengine bevel gear is carried out. It is obtained that both the driving bevel gear and the driven bevel gear have two pitch diameter, two order front traveling wave and rear shape wave resonance, and four pitch diameter, one order front traveling wave and rear shape wave resonance.

(2) Through contact analysis and calculation, the meshing stiffness of the central bevel gear of an aeroengine for each discrete time point is obtained, and the time-varying meshing stiffness of the central bevel gear pair is obtained by Fourier transform, and the time-varying meshing stiffness calculation method of the central bevel gear of aeroengine is formed.

(3) According to the general dynamic model of gear transmission system, considering the transmission shaft and central transmission rod, and introducing time-varying meshing stiffness, the dynamic model of aeroengine central bevel gear transmission system is established. The nonlinear dynamic equation of aeroengine central bevel gear transmission system is obtained. The time history of each dimensional displacement is obtained by using the variable step size adaptive Runge Kutta numerical integration method. Through the FFT analysis of the dimensional displacement of the driven bevel gear, it is found that the faulty bevel gear system has four response frequencies with large response amplitude, and two of them are consistent with the first-order and second-order resonance frequencies of the second pitch diameter of the driven bevel gear, which is at risk, Therefore, the resonance frequency of the 2 pitch diameter of the driven bevel gear should be avoided. It is also found that the input load is not the main reason affecting the vibration of bevel gear transmission system.

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