|Titel||Stribeck-type Curves of Alternative Engine Oils - Part I: Gray cast iron liners|
|Autor||Mathias Woydt, Norbert Kelling|
|Infos zum Autor||Mathias Woydt, Norbert Kelling
BAM Federal Institute for Materials Research and Testing, D-12200 Berlin
Falk Hannemann, Niklas Berberich, Holger Ziegele
BMW Group, D-80388 Munich
Wear tests are often used in engine development in order to characterize the functional profile of surfaces interacting with lubricants. This paper proposes a new test procedure to determine Stribeck-type curves for the tribosystem piston ring/cylinder liner involving test pieces prepared from engine components. The variation of the friction coefficient with sliding speed depends on the structure and constitution of the base oil, the viscosity index, the surface topography of the liner and ring, and the friction modifiers used. Novel organic friction modifiers of low molecular mass not only reduce the friction coefficients under mixed / boundary lubrication, but also in the fluid film regime. In addition, the influence of surface roughness on the wettability of surfaces can be significant for both static and dynamic wetting. For this reason, the interaction of the lubricant with the surfaces was also investigated to enable a correlation between the surface properties of the liquid and solid phases and the tribological behavior.