Study On Thermal Analysis And Contact Fatigue Life Of The Main Reducer Gear Of Shield Machine

Modern tunnel shield construction requires more and more life of the shield machine.The reducer of shield cutterhead main driving is the core component of cutterhead driving system.The adequate design life of the reducer is the guarantee of shield tunneling smoothly.With the increasing of shield market,it is imperative to localize the main reducer.And the problem that the working temperature of domestic reducer is too high must be solved.Fatigue damage of gears is inevitable for the reducers,and the temperature of gears is closely related to their contact fatigue life.Therefore,it is necessary to study the temperature field and contact fatigue life of the reducer gears.This paper takes the reducer designed for a metro construction in Chengdu as the research object,and studies the temperature field of the gear and the effect of temperature rise on gear meshing and the contact fatigue life.The main contents of this paper are as follows:1?By calculating the cutter head torque of the shield machine under tunnelling conditions,the load of reducer is determined.Combining with the mechanism principle of NGW planetary gear,the calculating model of the transmission torque and speed between gears at all levels is obtained.2?The relative sliding speed,contact stress and friction coefficient of gears at each meshing point are obtained by using the knowledge of gear meshing principle,Hertz theory and tribology,and the calculation model of average friction heat flux at each meshing point is established.3?Based on the knowledge of heat transfer and fluid mechanics,the heat conduction conditions and the corresponding calculation method of convective heat transfer coefficient on each surface of gears are determined.The corresponding finite element analysis model is established by ANSYS,and the steady temperature field of the gears of the reducer is obtained by simulation.4?From the point of heat generation principle and heat dissipation condition of the reducer gears,the external factors such as load,physical characteristics of gear oil,temperature of gear oil,working environment of the reducer,and internal factors such as various design parameters of gears,are analyzed.Combined with numerical analysis,the influence of two design parameters,tooth width and deceleration ratio,which are related to heat generation and heat dissipation,on gear temperature is emphatically analyzed.5?The contact finite element model of the reducer gear is established,and the conventional contact stress distribution of different meshing points is obtained by simulation.Then the thermal coupling contact simulation of the gear is carried out considering the influence of thermal deformation.Thermal coupling contact stress distribution of each meshing point is obtained.The results of the two models are compared and analyzed,and the influence of temperature rise on the meshing characteristics of the gear is studied.6?Through the cutter head load characteristics in shield tunneling,the load distribution law of the reducer is obtained,and the load spectrum of the reducer gear is established based on finite element contact analysis.In addition,the contact fatigue S-N curve suitable for the reducer gear is obtained by modifying the material contact fatigue S-N curve.Finally,the contact fatigue life of the gear is estimated by using the linear fatigue cumulative PalmgrenMiner theory.