Correlation Mechanism Between Film Forming Ability Of Grease And Bearing Fatigue Life

In this thesis,11 kinds of greases are divided into four types of greases,including different consistency,different base oil viscosity,different base oil and different additive greases.Rheological property differences caused by different grease composition are analyzed through rheological property testing,and the influence law of different grease composition on film forming ability is clarified through oil film thickness testing.The influence law of different grease composition and film forming ability on bearing fatigue life was revealed by bearing fatigue life test.Firstly,the rheological properties of all greases are tested.In steady-state measurement,the apparent viscosity of all greases decreases with the increase of shear rate,showing the properties of power law fluid.In the dynamic measurement,230 conein grease,220 viscosity grease,ester oil grease and Mo DDP grease show higher energy storage modulus,platform modulus and flow stress in the same type of grease,respectively,indicating that the thickener tangling or aggregation degree is high and the fluidity is poor in the same type of grease.Secondly,the oil film thickness of all grease is tested,and the influence of the composition of grease on film forming ability is analyzed through the rheol ogical characteristics of grease and the structure of thickener.The oil film thickness of all grease formed under the action of large load is small,because the increase of load can enhance the contact pressure between the rolling body and raceway and affect the supplement of grease in the contact area,resulting in the formation of a small oil film thickness.When the load is fixed,the oil film thickness of the grease increases with the increase of the rolling speed.The 230 cone entry grease forms a thicker oil film because of its high content of thickener,better rheological property and colloid stability,and the 220 viscosity grease forms a thicker oil film because of its better rheological property and colloid stability.Mineral oil grease forms thicker oil film because of its high content of thickening agent and large viscosity coefficient,additive grease forms thicker oil film because of its good rheological property and friction protective film.Finally,the bearing fatigue life of all greases is tested,and the influence of the composition of greases on the bearing fatigue life is analyzed through the rheological characteristics,friction and wear and film forming ability of the greases.230 taper grease,220 viscosity grease,mineral oil grease and additive grease have better film forming ability and friction performance,which is conducive to extending the fatigue life of bearings.The experimental data of grease film thickness and bearing fatigue life are analyzed in this thesis,and the correlation mechanism between grease film thickness and bearing fatigue life is expressed by mathematical model.