Experimental Study And Theoretical Analysis Of Behaviors Of Traction Characteristics For Two Kinds Of Bearing Grease

The traction characteristics under different conditions of lubricant are necessary design basis of bearing. Elastohydrodynamic traction force is one of the most difficult parameter, which is also very important in the practical application. In theory, the traction force can be calculated by solving equations of the rheological properties of lubricant. Because of the limitations of the constitutive equation itself, it is difficult to get accurate results of traction force. Traction force got by the experiment that simulate the working condition is the most reliable data.In order to simulate the rheological behavior of rolling bearing lubricants in actual operation process, experts have designed traction testers with different structure. This paper introduces a ball-disc test machine, which has been proved accurate and reliable through many years’ simulation experiments. In this experiment, this paper studied the traction characteristics of grease LGHB2and grease LGHP2on the traction testers. The regulations of traction coefficients of two kinds of lubricating grease changing with the slide-roll-ratio, load and speed are obtained. The traction characteristics of the two kind of grease are compared. The study found that there are limiting speed when grease LGHB2working in the range of experimental speed (5m/s-40m/s).When the speed exceeds20m/s, grease LGHB2traction coefficients did not decrease with the increase of the speed.Based on the Herchel-Bulkley model, relationship among the slide-roll-ratio and the traction coefficient was formulated. This paper use the relationship to fit the result of the experiment, there is a big difference between the result of calculation and that of the experiment. The corrected model based on Herchel-Bulkley model conform to the traction characteristics of grease LGHP2and grease LGHB2.The exponential model with four parameters is the pure mathematical formula that some experts used to fitting traction coefficient. The previous did not propose any rheological significance for the mathematical formula. This paper tries to chang the mathematical formulation and explores the physical meaning of the expression obtaining some parameters’ significance. In the study, it is found that the exponential model with four parameters can be further simplified. Using the simplified model to fit traction coefficient is more easily. As the fitting results show, a simplified formula has very high precision when the traction curve ascend. But when the traction curves decent, there is a large error. Finally, the polynomial is used to fit the experimental data, and good results were obtained.This project provided traction data of the two kinds of lubricating grease for engineering application. Some preliminary works such as exploring the applicability and rheological significance of model have done. It lay a certain foundation for the future work.