Study On Elastohydrodynamic Rheological Properties Of The Lubricating Grease At High Shear Rates

In this paper,the rheological properties of grease under high shear rate elastohydrodynamic lubrication were studied.The most widely used lubricating greases are lithium lubricating grease and polyurea lubricating grease.The base oils are PAO synthetic oil,polyol ester oil and paraffinic mineral oil.First,the friction characteristics of the lubricating grease were tested by the mini-traction machine(MTM2).The rheological curve of the lubricating grease was obtained by calculation,and the rheological characteristics of the lubricating grease were further analyzed.The effects of rolling speed,load,temperature,thickener,base oil and consistency on the rheological properties of lubricating grease were analyzed by changing a single variable.which can provide some reference for the research and application of lubricating grease.The rheological properties of lubricating grease are affected by many factors.Working condition is an important factor affecting the rheological properties of lubricating grease.The mini-traction test machine(MTM2)can simulate friction and lubrication under a variety of working conditions to achieve a single variable change.According to the test data,the influence of different working conditions on the rheological properties of lubricating grease was analyzed.The results show that the shear stress decreases with the increase of rolling speed and temperature,increases with the increase of load.Lubricating grease is composed of thickener and base oil.The three-dimensional structure of different thickeners is different,and the chemical composition of different base oils is different.The composition of grease has an important influence on the rheological properties.Compared with the grease obtained by thickening mineral oil with lithium-based thickener,the grease obtained by thickening synthetic oil has better lubricating performance.The shear stress of the grease obtained by thickening mineral oil with lithium base thickener is smaller than that obtained by thickening mineral oil with polyurea thickener.and the influence of the consistency on the rheological properties is different at different temperatures.According to the changing trend of the rheological curve of lubricating grease,the four parameter model is used to fit the rheological curve of No.3 lubricating grease,and the error between the calculated value and the test value is small.This model can be used as a reference for the calculation of rheological properties of this kind of grease.After the grease has been sheared for a long time in practical use,the mechanical attenuation phenomenon occurs,the three-dimensional network structure formed by the thickener fiber is damaged,the consistency is reduced,the adhesion is reduced,and the rheological properties are also changed.In this paper,a lithium-based grease was sheared at different times to simulate the mechanical attenuation of the grease.Through the analysis of its rheological curve,it is found that the greater the attenuation degree,the greater the decline of the lubricating performance of the grease.In this topic,several factors influencing the rheological properties of lubricating grease are analyzed,and analyzes the reasons,which provides a reference for the research and application of lubricating grease.