PhD in 2017

date: 04.07.2017

In July a PhD thesis defence took place within the Laboratory for Tribology and Interface Nanotechnology.

Dr. Kosta Simonović: Model for the Friction prediction of the Diamond like Carbon Coatings (DLC) in the Boundary Lubrication Conditions

This Ph.D. thesis studies individual and synergistic contributions of the Anti-Wear (Zinc dialkyldithiophosphate, ZDDP), Friction-Modifier (Glycerol isostearate, GIS) and Automotive additive package to the friction of the steel and DLC contacts across a broad range of boundary-lubrication contact conditions. A design-of-experiments was used to enable broad-range experimental matrix and Elastic-net regression technique was used to develop friction models and friction maps depending on the most relevant contact parameters, namely pressure, roughness, speed, and temperature. Moreover, obtained models are based on the experimental parameters and their interactions whose statistical significance has been undoubtedly proven. The major conclusion is that statistically identified interactions of the experimental parameters show which of the parameters interfere and compete in their influence on the coefficient of friction, hence, which of the investigated parameters must be simultaneously considered if proper conclusions are to be made. What is more, it is shown that single parameter investigations of the boundary lubrication regime do not reveal true properties of the contact/lubricant combination in the whole range of the boundary lubrication regime.