Research On Nonlinear Dynamic Characteristics Of Gear Transmission System With Pitting Fault Considering Friction And Temperature Factors

Gear transmission system is the most important and commonly used transmission device.Under different working conditions,the gear pair is subjected to periodically varying contact stress.When the contact stress exceeds the contact fatigue strength of gear tooth material,pitting pits of different shapes will be formed on the surface or subsurface of gear teeth,and the pitting corrosion will rapidly evolve from initial pitting to extensive pitting,The appearance and expansion of pitting corrosion will lead to the loss of metal materials on the tooth surface,change the geometric size and nonlinear dynamic parameters of the gear pair,and lead to the change of the dynamic characteristics of the system,which will affect the stability,reliability and fatigue life of the system,and produce a lot of noise at the same time.Therefore,this thesis takes the traction spur gear transmission system of HXD2 heavy haul locomotive as the research object,analyzes the influence of the appearance and expansion of pitting on the time-varying mesh stiffness,time-varying friction coefficient and tooth surface contact temperature,and studies the influence of pitting fault on the dynamic characteristics of gear transmission system when considering different factors.Firstly,based on the probability model of normal distribution of pitting failure,four probability models of normal distribution of pitting pits with different failure degrees,including no pitting failure,slight pitting failure,moderate pitting failure and severe pitting failure,are established.The influence of pitting failure on time-varying meshing stiffness is mainly analyzed.Then,the types and calculation methods of dynamic excitation such as internal excitation,external excitation and random disturbance excitation are briefly analyzed.Secondly,based on the friction coefficient calculation model of elastohydrodynamic lubrication theory,the influence of tooth surface pitting on the time-varying friction coefficient is analyzed,and the dynamic model of the gear transmission system considering only the tooth surface friction factor is established by the lumped mass method,and the influence of pitting fault expansion on the dynamic characteristics of gear transmission system is studied when the pitting fault coefficient and meshing frequency are taken as bifurcation parameters.In addition,based on the calculation model of tooth surface flash temperature and temperature stiffness,the influence of tooth surface pitting fault on tooth surface contact temperature is analyzed,and the temperature stiffness caused by tooth surface thermal deformation caused by tooth surface friction is calculated,Furthermore,the influence of pitting fault expansion on the dynamic characteristics of gear transmission system considering friction temperature factor is studied when the pitting fault coefficient and meshing frequency are taken as bifurcation parameters.Then,the bifurcation and chaos of pitting fault system at low frequency and high frequency are compared and analyzed under the conditions of considering and not considering the temperature factor.Finally,Monte-Carlo method is used to simulate the random disturbance of each parameter of the system,and the random dynamic model of the pitting fault gear transmission system is established.The influence of the random disturbance of time-varying meshing stiffness and meshing frequency on the dynamic characteristics of the pitting fault gear transmission system is analyzed.Then,the choose principle and method of the reasonable matching of the system parameters after the occurrence of pitting failure are analyzed through an example,and the stable motion interval of the system is given under the specific system parameters.