| Lubrication grease is an important component of a bearing,which has an significant influence on bearing life.It is great significant for prolong the fatigue life of bearing to research bearing fatigue life based on grease lubrication.This paper analyzes the phenomena of starved lubrication under grease lubrication,and points to the contradictions lubrication design combined with practical application of bearing.The different additives are selected and added into the polyurea greases.These samples are used to carry out experimental research on the fatigue life of grease lubricated deep groove ball bearings.This study points out the research direction for prolonging the fatigue life of grease lubricated bearings.The theoretical value of base oil film thickness is calculated under the fatigue life test conditions.The starved lubrication state of grease is simulated by EHD2 optical interference film thickness meter,and the starved lubrication state is confirmed under the condition of the bearing fatigue life test.The influence of different additives on the fatigue life of the grease lubricated6308 bearings is investigated by ABLT-1A bearing fatigue life test machine.The extreme pressure(EP)and anti-wear(AW)performance of lubrication greases is analyzed using four ball machine and SRV test rig,the result shows that good P_B or small scar diameter of the four ball test is necessary for greases that can prolong the fatigue life of bearing.The suitable sulfur and phosphorus anti-wear(AW)agents can improve the fatigue life of bearings under starved lubrication.Because the sulfur and phosphorus anti-wear agents can react with steel in rolling bearing formed the reaction film on the surface of the steel ball and groove,which can reduce the surface fatigue flake.The fatigue life of grease lubricated bearings is extended by 2.67~3.68 times compared with the theoretical calculation value by using the additive S1 and P1.Non-active sulfur additives are more effective for extending the bearing fatigue life than additives containing active sulfur in grease lubricated bearings.Because bearing steel will be corroded excessively by active sulfur additives under high temperature,which will cause increased wear that result in increased bearing vibration.In addition,the premature oxidation of grease will affect the fatigue life of the bearing.The main reason is that the sludge and varnish adhesion to the steel ball and the rolling surface causes the increase of the RMS value of the bearing vibration.Excellent oxidation resistance and anti-wear capacity of grease is the key point to prolong the fatigue life of the bearing. |
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