Research On Nonlinear Dynamic Characteristics Of Locomotive Gear Transmission System

The transmission system is the core component of locomotive,whose function is to transfer the output power of traction motor to wheelset.As so,the transmission system plays an important role in ensuring the power transmission and normal operation of locomotive.However,the breakdown/damage problem of the component parts of locomotive transmission system become more and more prominent due to the complicated working environment and frequently changing operating conditions,which brings hidden dangers to the performance and safety operation of locomotive.However,in the traditional vehicle system dynamics,researchers does not pay sufficient attention to the nonlinear excitation factors of internal components of transmission system when studying the vibration problem of locomotive.The failure or wear of the internal components of locomotive transmission system has not been well solved.Therefore,in order to ensure the safe service of transmission system and the locomotive,there is an urgent need to study the vibration characteristics of the locomotive transmission system components more deeply.Gear transmission system is usually used in the current service locomotive.Therefore,when the locomotive gear transmission system is in service,it needs to bear the internal nonlinear excitations from gear mesh and supporting bearing et al.At the same time,as one part of locomotive,the gear transmission system will be affected with the associated locomotive components each other.So,this thesis carried out the study on nonlinear dynamic characteristics of locomotive gear transmission system,which including the following two aspects: the nonlinear vibration characteristics of locomotive gear transmission system and the dynamic behavior of locomotive affected by the nonlinear vibration of gear transmission system.The main contents are as follows:(1)Studying on the parametric vibration stability of locomotive gear transmission system based on the analysis method of vibration stability of parametric system.Firstly,the time-varying stiffness of gear pair of one locomotive was calculated based on the potential energy principle.And the error,clearance and tooth surface friction excitation of gear pair were described too.Then,the expressions of parametric vibration stability of locomotive gear transmission system,which under the models of two degrees of freedom torsional vibration,multi-degree of freedom torsional vibration and coupled vibration,were obtained by the means of multi-scale analytical method.The numerical simulation were carried out to verify the correctness of the expressions.The characteristics and differences of the parametric vibration stability of system under the above three models were revealed too.(2)Studying on the nonlinear vibration response of locomotive gear transmission system based on the nonlinear characteristics of gear mesh and wheel-rail contact.Firstly,the frequency response equations of locomotive gear transmission system in main resonance and harmonic resonance were derived by multi-scale analytical method.The amplitude-frequency response,time-domain and frequency-domain characteristics of locomotive gear transmission system in resonance were simulated.Then,the influence of gear mesh and wheel-rail contact on the amplitude of system were studied when wheel-rail contact is in the stick-slip zone and sliding zone respectively.(3)Establishing the dynamic analysis model of locomotive including the internal gear-rotor-motor bearing components of gear transmission system based on it's structural feature.Firstly,the additional forces when considering the internal gear-rotor-motor bearing components of gear transmission system were analyzed.Detailed force analysis and calculations were carried out for each part of locomotive.Then,the mathematical model of locomotive vibration were derived.The corresponding locomotive dynamics simulation analysis program was compiled by MATLAB software.(4)Studying on the locomotive vibration under the influence of nonlinear excitation of gear mesh based on the traction and braking characteristics of locomotive.Firstly,for the traction/braking conditions,the difference between the vibration characteristics of locomotive in the time-domain and frequency-domain under the two kinds of models(considering the gear mesh excitation or considering the gear ratio)were analyzed.At the same time,the wavelet analysis method was used to reveal the time-frequency domain characteristics of locomotive parts under the two models.Then,for the traction condition,the vibration characteristics of locomotive considering gear mesh excitation under different gear pair installation positions was analyzed.(5)On the basis of considering the nonlinear excitation of gear mesh,the effect of motor bearing excitation was further considered,which is based on the nonlinear excitation characteristics of the bearing components.The vibration characteristics of locomotive under the influence of the nonlinear excitation coupling of motor bearing and gear mesh were studied.