Research On Rheological Properties And Performance Correlation Of Lithium Base Grease

In the bearings industry grease is applied widely. The special rheological properties of grease are closely related to its performance, the effect of the rheological properties of the grease on the friction and wear properties and the starting performance of the bearing are studied. People can be with the rheological characteristics to evaluate the quality of lubricating grease, to choose different grease in different conditions.In this paper, 12 kinds of grease with different NLGI grades were prepared by naphthenic base oil and paraffin base oil as raw materials and their physical and chemical properties were compared. The paddle rotor rheometer, four ball friction and wear tester, torque tester, vibration tester were selected as the test equipment, the experiment scheme was designed.The correlation between rheological properties and tribological behavior was studied. First the influence of apparent viscosity on the friction coefficient of the grease and the correlation error analysis on the test scheme were discussed. Secondly the influence of apparent viscosity and viscosity-shear curve on the friction coefficient, the diameter of wear spot was obtained in light load and high speed, low speed and heavy load, moderate speed and load conditions. Finally the influence of speed, temperature and load on the correlation was discussed. The influence of the apparent viscosity caused by different factors on the friction and wear properties is not entirely consistent.The correlation between the rheological properties and the starting performance of the grease bearing was studied. The friction torque test and the rheological test showed that the yield stress had a key effect on the starting friction torque. The yield stress increased, starting friction torque became higher. At the same time, the elastic modulus and thixotropic of grease had an effect on the friction torque variation. elasticity modulus and thixotropy increased, shear thinning phenomenon became more obvious, grease state became fluctuatinger, the change of friction torque became bigger.The correlation between the rheological properties and the vibration noise of the grease bearing was studied. The vibration of two kinds of bearing was tested. The influence of thixotropy, elastic modulus on the average value of vibration and peak frequency in low frequency, intermediate frequency and high frequency was analysed. In a certain range, thick content of grease, small apparent viscosity, low elastic modulus, little thixotropy is conducive to the bearing vibration and noise reduction.