Oil Film Stiffness Model And Parameters Analysis For Modified Spur Gear Based On Elastohydrodynamic Lubrication

Lubrication failure is one of the major forms of gear break.The oil film rupture will lead to the direct contact between mesh gear teeth,resulting in the violent friction and local high temperature rise.Furthermore,it may cause the gear wear,scuffing and fatigue failure.Gear transmission is moving toward the development direction of high speed,heavy load and high precision.Therefore,it makes the problem of gear vibration,impact and noise in gear dynamics responses more and more serious.In this paper,it takes the modified spur gears as research object,based on the non-Newtonian elastohydrodynamic lubrication(EHL),the model of line contact EHL for spur gear drive is established.The effects of fundamental parameters and fluid rheological models on EHL properties are discussed.The models of oil film stiffness in normal and tangential direction are established,and the normal and tangential oil film stiffness is calculated along the line of action.The effects of operation parameters and geometry parameters for spur gear on oil film stiffness are investigatecd.Finally,the effect of oil film on gear transmission is analyzed which provides tribology theory basis for mesh impact reduction and stationarity enhancement of gear drive.The main contents includes:The establishment of EHL model in line contact and application in spur gear drive.An EHL model in line contact is established and the oil pressure is acquired by multi-grid method.The effects of applied load,entrainment velocity,and comprehension curve radius on EHL are investigated.Afterwards,the model is applied in spur gear drive and the variations of load,entrainment velocity,and comprehension curve radius along the line of action are investigated.Finally,the oil pressure,film thickness,shear stress and fluid velocity in five characteristic points of the gear mesh process are studied.The results show that the load play the important role in oil pressure and oil film.The comparison between Newtonian model and various non-Newtonian models.The equivalent viscosity of non-Newtonian fluid is computed,and the complete numerical solutions have been obtained for non-Newtonian EHL.Considering the fluid rheology,the effects of Ree-Eyring fluid and power-law fluid models on EHL are studied.Then that the effects of Ree-Erying fluid and Newtonian fluid on oil pressure,film thickness,and frictional coefficient are also investigated.The results show that the power-law index has an important effect on film thickness and that the friction coefficient of Ree-Erying fluid is smaller than that of Newtonian fluid.The models of oil film stiffness Based on non-Newtonian EHL and application in modified spur gear.Based on non-Newtonian EHL,in the direction across the oil film,the normal stiffness model of oil film by the viscoelasticity fluid being equivalent to the massless spring.In the flow direction,the tangential stiffness model of oil film fluid is proposed according to the hypothesis of equal shear stress on laminar element surfaces.The effects of various operating parameters(contact force and rotation speed)and geometry parameters(module,tooth number,pressure angle and modification)on the oil film stiffness along the line of action from the root to the tip are investigated.The results show that the less fluctuation of oil film stiffness at single-to-double and double-to-single tooth contact due to the load change is are valid in mesh impact reduction.The modifications are beneficial to fluctuation reduction of oil film stiffness and stationarity enhancement.