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Under current regulations, gasoline engines are facing lubricity and wear challenges that need to be met by enhanced gasoline lubricity. Gasoline lubricity can be enhanced by lubricity improvers such as heavy fatty acid methyl esters. This thesis presents the ‘High Frequency Reciprocating Rig’ (HFRR) tests carried out on a standardized tribological test rig as per a modified version of ASTM D6079, to account for the effects of volatility of gasoline. Testing 5 gasoline types (gasolines A-E) blended with 2 lubricity improver types (LI1-2) at 2 concentrations, 250 and 500 ppm, provided insights on the changes in lubrication behavior with different gasoline composition, LI type, and concentration. The gasoline types with higher aromatic content and average carbon number (lower volatility) resulted in less wear and better lubricity regardless of LI concentration. The highly aromatic gasoline “A” performed better with the fatty acid-based LI1. Gasolines “B-E”, which are less aromatic, resulted in less wear with the ester-based LI2. The decrease in wear volumes with LI2 was more pronounced with the highly volatile gasolines B and E. These insights were mainly challenged by the failure of some tests due to the high volatility of gasoline. To mitigate this effect and confirm the findings, less volatile gasoline surrogates were designed to mimic the composition of the gasoline types on functional group basis, and were blended with the same lubricity improvers, and then tested using the same method. This improved the results and showed that high aromaticity enhanced the lubricity of the gasoline blends, especially with fatty-acid based LI1, but degraded it beyond 50% aromatic content. The enhancement of lubricity with higher average carbon number was also highlighted. To create deeper understanding of the lubrication mechanisms involved, it is recommended to study the rheological properties of the blends, analyze the chemical composition of the deposits on the wear tracks, and repeat the tests with continuous supply of lubricant to further decrease the effect of gasoline volatility

<p> This thesis is a study of the adhesive behaviour of HeLa cells using a novel instrument designed for measuring both the shearing and compression force applied to the cells. For these experiments a micropipette forged as a double cantilever is used to grasp and manoeuvre a cell onto a silicon or Poly-L-Lysine (PLL) coated substrate. The substrate is then moved perpendicularly with respect to the micropipette tip thereby sliding and shearing the cell across the surface. The perpendicular and parallel deflection of the cantilever enables us to directly measure the friction and normal force. A new approach for calibrating both sections of the cantilever has been developped and will also be presented in this work. As a proof of concept, the experiment is also performed with a polystyrene bead. The polystyrene bead, a simpler system, manifests some of the typical results expected from friction experiments. </p> / Thesis / Master of Science (MSc)

Load controlled cyclic fatigue testing was conducted on base metal (BM) and friction stir welded (FSW) magnesium (Mg) alloy AZ31B compact tension (CT) specimens in laboratory air and a 0.05 wt. % NaCl fog environment in efforts to delineate the effects of salt fog and stir welding on fatigue performance under tension-tension loading conditions. FSW beads were produced on single piece AZ31B sheet product, simulating a pristine friction stir butt weld. Optical and electron microscopy, as well as X-ray diffraction was employed to observe the features and characteristics of fracture surfaces. The resulting stress vs. number of cycles to failure (S-N) curves demonstrated a reduction in fatigue life in a salt fog environment and an increase in fatigue life for FSW specimens compared to equivalently loaded BM specimens. Tensile frame displacement data indicated that the salt fog environment had an immediate effect on the BM samples, with an increased displacement required to meet the load control criteria. Fatigue cracks that propagated in CT samples that were notched in the direction of FSW tool travel consistently propagated towards the retreating side (RS) of the stir zone. / Thesis / Master of Applied Science (MASc)