| Summary: | The general trend towards the use of high performance lubricants and environmentally friendly products supports the design of new industrial lubricants. Therefore, there are good practical reasons to extend the research related to lubrication. Bio-oils, as promising growing substitutes for mineral oils, need more research to deal with new and inherited problems. Meanwhile, there is no complete understanding of the lubrication phenomenon, nor a complete rheological characterization of oil lubricants. This research is an effort to study industrial bio-lubricants and to develop a more comprehensive approach, at the same time correlating their rheological and tribological behavior.
Different commercial canola oil based lubricants were studied using different techniques. For validation and comparison, engine oil, silicone oil and mineral hydraulic oil were tested. Bio-lubricants exhibited constant viscosity at both moderate and high shear rates and shear thinning at low shear rates and temperatures below 30 degrees Celsius. Frequency sweep tests revealed a significant viscoelasticity of bio-lubricant which developed over time.
Time dependence, structure recovery, gap size effect, surfactant behavior, and geometry’s material influence were all investigated. A high pressure cell and a polarized light microscope coupled with the rheometer were used to investigate the bio-lubricants.
Thermal analysis was conducted using a differential scanning calorimeter. Several transition points were identified in the range of temperatures from -30 to 100 degrees Celsius, and the results have been connected to the viscoelastic behavior.
Different tribological tests were used to investigate the lubricity of lubricants and bio-lubricants added by liquid crystals. The coefficient of friction, at tested temperatures, and the wear rate were observed over time. Adding two percent of ionic liquid crystals improved the wear resistance of the oil, but the bio-lubricant had the lowest coefficient of friction.
This research could be considered as pioneer work. An attempt was made to achieve profound perspective matching between rheometry, tribology and thermal analysis. Some assumptions explaining the rheological and tribological behavior were hypothesized and associated with arguments and discussions. Based on, Imaginary scenario of bio-hydraulic oil behavior within a small gap was visualized. === Applied Science, Faculty of === Mechanical Engineering, Department of === Graduate
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