| In this thesis,experiments were carried out to explore the tribological characteristics of three trimellitates,three pentaerythritols and two novel friction modifiers SE and GI.Firstly,on a ball-disk point contact test rig using optical interferometric technique,the film thickness in elastohydrodynamic lubrication(EHL)contacts were measured for the three trimellitates,the three trimellitates with 3% polymethacrylates(PMA)as additive.It is found that the addition of PMA can increase the viscosities of the trimellitates but exert no influence on the film thickness.Then,using a SRV-V friction and wear test apparatus,the influence of adding 3% PMA on the variations of friction and wear volume in boundary lubrication was investigated under different temperature and load conditions.Generally the addition of PMA can reduce the friction coefficient,but the effect is limited under high temperature and high load conditions.Secondly,three pentaerythritols with different molecular structures were chosen to study the film formation,wear resistance and friction reduction performance.The optical interferometric EHL experiments show that the increase in the hydrocarbon chain can increase the viscosity of the pentaerythritols as well as the EHL oil film thickness.The friction and wear experiments illustrate that with the increase in the molecular chain length,both the friction coefficient and wear volume are reduced under different load and temperature conditions.However,for all three pentaerythritols,with the increase of the load,temperature and working frequency,the wear volume is increased,illustrating the deterioration of wear-resistance.At last,using a four-ball test rig,the tribological performances of two novel synthetic ester based friction modifiers(SE and GI)added in PAO 4 and 5w-30 were explored and compared with that of a traditional friction modifier GMO.The results show that both SE and GI can reduce the friction coefficients of base lubricants PAO and 5w-30 as while as increase the wear resistance property.The PDSC experiment demonstrates that SE exhibits a good anti-oxidation property in PAO 4 and 5w-30. |
