The objective of the research project was the investigation of lubricant film formation in elastohydrodynamic contacts for oils of different origin (paraffinic, naphthenic, polyalphaolefin) and various types of VI-improvers (polymethacrylate, olefin copolymer, styrene butadiene copolymer). An essential part of the research was to find out whether VI-improvers maintain their thickening effect under contact conditions of high pressure (p=10,000 bar) and temperature (ϑ=50-90 °C), high shear rate (γ̇=106 s-1) and short contact time, all these conditions occurring simultaneously. A twin disk machine was used to determine values of film thickness in a line contact. For these measurements, an electrical capacitance method was used. In addition to a thermal viscosity loss, high shear rate γ̇ leads for VI improved oils to temporary viscosity loss and thus reduced film thickness. Additional permanent viscosity loss due to shear thinning reduces measured film thickness further. Lubrication with non-Newtonian fluids results in higher film thickness compared to their base oil but, even for pure rolling, in thinner films as a Newtonian fluids of same nominal viscosity.
Film Thickness in Highly Loaded Contacts - Influence of Various Base Oils and VI-Improvers
Sae Technical Papers
International Fuels & Lubricants Meeting & Exposition ; 1996
01.05.1996
Aufsatz (Konferenz)
Englisch
Film thickness in highly loaded contacts - influence of various base oils and vi-improvers
Kraftfahrwesen | 1996
|Viscosity index improvers for lubricating oils
Kraftfahrwesen | 1990
|Influence of VI Improvers on the Operating Temperature of Multi-grade Gear Oils
British Library Conference Proceedings | 2000
|Solution viscosity studies on OCP VI improvers on oils
Kraftfahrwesen | 1989
|An "In Lubro" study of VI improvers in EHD contacts
Kraftfahrwesen | 1990
|