弹流润滑对齿轮接触疲劳寿命影响研究

Gear Contact Fatigue Under Elastohydrodynamic Lubrication

现有齿轮传动接触疲劳强度校核主要以干接触下最大赫兹应力为指标,而齿轮往往是在润滑条件下工作,且受时变次表面应力场的作用。本文结合齿轮几何学、运动学参数及润滑特性,考虑接触曲率半径、卷吸速度、齿间啮合力等时变量,建立齿轮弹流润滑接触分析模型;利用DC-FFT算法求解次表面应力场,结合临界平面疲劳准则,研究齿轮接触过程中的疲劳寿命和裂纹萌生机理,讨论工况变化对疲劳寿命影响规律。结果表明:弹流润滑条件下齿轮疲劳寿命相对于赫兹干接触有明显提升,这是由于齿面压力变化导致的次表面应力场变化改变了临界平面角,使等效疲劳参数减小,齿轮接触疲劳寿命增加;输入扭矩的增加将大幅降低疲劳寿命,二者变化呈现非线性关系,且会使裂纹萌生位置远离齿面,在等温牛顿流体情况下,转速变化对疲劳寿命的影响相对较小。

The existing method of the fatigue strength check of gear is mainly based on the maximum Hertz stress under dry contact conditions.However,gears always operate under lubricant conditions,and meanwhile subject to the time-dependent stress which below the tooth surface.Combining the geometry and kinematics parameters of gear as well as the lubricant characteristics,agear contact analysis model of elasto-hydrodynamic lubrication（EHL）is established considering the transient variables,i.e.,the curvature radius,the entrainment velocity and the mesh force.The sub-surface stress field solved by DC-FFT algorithm is combined with the critical plane criterion to study the fatigue life and creak initiation during the gear engagement,and to discuss the influence of work condition on the fatigue life.The results show that the fatigue life under EHL is higher than that in the Hertz dry contact.This is due to the change of critical plane angle affected by stress field and pressure,which influences the fatigue parameter and fatigue life.And the fatigue life significantly decreases in nonlinear with the increasing input-torque,thus keeping the position of crack initiation away from the tooth surface.The fatigue life hardly changes with the increasing speed under Newtonian isothermal fluid.