| In this paper,the high shear rate elastohydrodynamic lubrication characteristics and lubrication mechanism of lubricating greases with different base oil types under the condition of sufficient grease supply are studied.Using MTM2 micro-traction testing machine,the working state of grease in rolling bearing was simulated,the friction coefficient of grease and its base oil was tested under different working conditions,and the influence of single working condition on the friction characteristics of grease was studied by controlling single variable method.The differences of friction coefficients of three kinds of lubricating greases were analyzed,and the friction coefficients of lubricating greases and their base oils were compared under the same working conditions.According to the test,three kinds of base oils and three kinds of lithium-based lubricating greases of different base oils were prepared,namely,PAO synthetic oil,polyol ester oil and paraffinic mineral oil,and three kinds of corresponding lithium-based lubricating greases.The viscosity temperature characteristics of three kinds of base oils were studied,and the motion viscosity-temperature model was fitted by the Vogel viscosity model,the results showed that the measured model and the calculated model had a high consistency,then the Vogel viscosity model of PAO synthetic oil,polyol ester oil and paraffin based mineral oil were established respectively.The effects of working conditions on the friction characteristics of three lubricating greases and their base oils are studied.The results found that: when the roller is less than 10%,grease and the friction coefficient of base oil is linear increase with the increase of roller than when the roller is increased to 10%,with roller than continue to increase,the grease and its base oil of the friction coefficient increases with the increase of roller than is nonlinear,trend slow or reduce a little.The friction coefficient of grease and its base oil decreases with the increase of rolling speed.The friction coefficient of the grease and its base oil increases with the increase of the load.Among them,under high sliding and rolling ratio,the friction coefficient of lithium base lubricating grease and mineral oil decreased obviously,the friction coefficient decreased the most,and the thermal effect was obvious.The friction coefficient of grease and its base oil decreases with the increase of ambient temperature.The influence of base oil type on the friction characteristics of lubricating grease was studied,and the lubrication mechanism was analyzed.The results found that: in the three grease PAO lithium base grease in the smallest friction coefficient,the friction coefficient of mineral oillithium base grease,the largest PAO synthetic oil minimum friction coefficient at the same time,the largest mineral oil friction coefficient,and under the same conditions and the friction coefficient of base oil,grease base oil has great effect on the friction characteristics of grease.It was found by high-power electron microscope that the grease distribution on the racetrack was different in different lubricating greases under the same working condition,and it was found by scanning electron microscope that the three-dimensional skeleton structure of lithium lubricating greases with different base oils was different.The composition of grease in contact raceway was analyzed by infrared spectrograph,and the difference of three kinds of grease was analyzed,but the deterioration of grease was not found. |
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