Experimentally derived friction model to evaluate the anti-wear and friction-modifier additives in steel and DLC contacts

Individual and synergistic contributions of Anti-Wear wear (Zinc dialkyldithiophosphate, ZDDP) and Friction Modifier (Glycerol isostearate, GIS) additives to the friction of steel and DLC contacts across a broad range of boundary-lubrication contact conditions are evaluated. A design-of-experiments was used to enable broad range experimental matrix and carefully selected regression technique was used to develop friction models and friction maps depending on the most relevant contact parameters (p, v, T, R-a). Apart from many specific conclusions, one of the major conclusions 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.