Research On Friction Characteristics Of Bearing Grease In Point Contact Under Medium-low Speed State

In modern industrial areas, the bearings are widely used in mechanical equipments in order to reduce friction coefficient and guarantee rotation accuracy during working. Now, most bearings use grease lubrication, which not only can reduce friction and resist wear, but also has rustproof and seal effect. Poor lubrication of the bearing often occurs in the course of work due to the operating temperature rising, the impact load and the differential sliding, etc., therefore, in the design of greaselubrication bearing, the properties of elastohydrodynamic friction based on the actual working state and antifriction and antiwear under different material matching pairs of the grease have become the most important factors deciding the service lifetime and dynamic characteristics of the bearing. For that reason, in this thesis, the properties of antifriction and antiwear of the LGHB2 grease developed by the company of SKF are investigated intensively. Meanwhile, we also analyze the characteristics of elastohydrodynamic friction of grease under simulated working conditions in order to provide theory reference and data support for research and development of highperformance bearings.In this thesis, the properties of antifriction and antiwear for LGHB2 grease using improved ball-disc friction and wear tester combining with scanning electron microscope and energy spectrum analyzer under different matching pairs and loads are investigated. Comparative analysis about the effects of antifriction and antiwear for this grease under different matching pairs and loads, as well as the friction and wear mechanism between matching pairs during lubrication were made. The research shows that the extreme pressure properties of antifriction and antiwear for this grease is relatively superior under the matching pair of GCr15 disc/GCr15 ball,the extreme pressure properties of antifriction and antiwear for this grease is not good enough under the matching pair of GCr15 disc/Si3N4 ball, and the extreme pressure properties of antifriction and antiwear for this grease is relatively worse under the matching pair of GCr15 disc(without heat treatment)/GCr15 ball.This thesis taking the test results of FVA3 standard oil as the reference, which were tested on the ball-disc tester of ICL and the double disc tester of Aristotle Univ., improves and debugs the original elastohydrodynamic friction testing machine. When the test machine is stable and accurate, the actual working condition of rolling bearing is simulated, and LGHB2 grease is tested. Through the analysis of the test results, the change law of the elastohydrodynamic friction coefficient changing along with slidingrolling ratio, loads and involution velocity is summarized; and the models applied to the grease at middle-low speed are discussed. The study shows that the change law of LGHB2 grease changing along with sliding-rolling ratio, loads and involution velocity is obvious, which indicates the grease has good performance at light and heavy loads and can work efficiently in a relatively wider velocity range. It can be seen from the fitting results of the T-J model that the model is only suitable to fit the curve of the elastohydrodynamic friction characteristics in relative weak thermal effect, and applicable to relative narrow ranges of load and velocity. However, the exponential model with four parameters can fit the elastohydrodynamic friction characteristics curve more accurately within the whole test, suitable to predict the lubrication performance of the grease in engineering.