Tribological And Rheological Properties Of Lubricating Base Oils

Lubrication is one of the main ways to reduce friction and wear at the contact and relative motion interfaces of components, decrease energy consumption, and prolong the service life of equipment. It is widely used in nearly all machinery. Lubricating oils, determined by their tribological and tribological properties, have different lubrication results.The work presented in this thesis is a portion of research projects, tiled “Interfacial mechanics analysis of mechanical transmission components” and “Typical rolling-sliding contact failure transition and realted material variation”, from the State Key Laboratory of Mechanical Transmission of Chongqing University. It is mainly focused on the physical properties, tribological performance, and rheological properties of several types of base lubricants(Mineral oils, Poly Alkylene Glycols, Polymerized Alpha Olefins and Esters). The physical properties of base oils and their friction characteristics are studied under the simply sliding condition of ball-on-disc point-contact. The chemical structure of these base oils and their lubrication properties are correlated. It is anticipated that the research results can provide useful information for new lubricant development and can be a reference for lubricaiton selection in related applications.Firstly, the kinematic viscosities of these base oils are studied at different temperatures as the basis for the investigation on the effect of fluid viscosity on their friction performance. Modeled fluid viscosity and test results are compared to confirm the experimental results. The results show that the kinematic viscosities are affected by temperature, and that the viscosity difference is realted to the variation of their chemical structure, viscosity index of Poly alkylene glycol oils is affected by ether linkage, and the benzene ring structure can affect the viscosity-temperature characteristics of ester lubricants.Then, the friction behavior and waer protection ability of the oils are explored by measuring friction coefficients with the ball-on-disc tribometer under different velocities and by evaluating wear of the three diemensional topograpgy change of the disk surface before and after each test. The results show that the friction performance of each base lubricant can be characterized by a typical Stribeck curve, and that the friction and wear properties can be corealted to lubricant molecular structures.Tension and rheological properties of each type of base lubricant are then investigated. Viscosity is observed at different shear rates, and the results are correlated to the chemical structure.Lubricant additives are studied for their influeneces on tension and rheological properties of each lubricant with additives added. The results show that the lubricant thickener can improve stretching, adhesive properties of lubricants, and their thickening ability are influenced by the content of additives and shear rate.