Bosman, R.

Schipper, D.J.

English

University of Twente Research Information

Microscopic Mild Wear in the BoundaryLubrication regimeR. Bosman and D.J. SchipperPhone +31-(0)53-4892476, e-mail R.Bosman@ctw.utwente.nlUniversity of Twente, Faculty of Engineering Technology,Laboratory for Surface Technology and Tribology, P.O. Box 217, NL 7500 AE EnschedeIntroductionMany applications run in the boundarylubrication regime e.g: cam-followers, pistonliner combinations and transmissions. Wearprediction in this regime is complex due tothe multi-physical nature of the problem.Figure 1: A CVT transmission normally operating inthe boundary lubrication regime.The boundary lubrication regime ischaracterised as: “A lubricated contactwhere the load is carried by the asperitiesrather than by the lubricant”. In this regimethere are three types of defence againstmetal-metal contact, as illustrated in Fig. 2.• Physical adsorbed layer• Chemical adsorbed layer• Chemical reaction layerFigure 2: Schematic build-up of surface layer.The first two layers are assumed to failthermally and the latter mechanically.Mild WearTo protect the metallic surface, constantrenewal of the surface layer is needed. Aslong as the removal and growth are inbalance mild wear occurs. The reactionlayer is build up from bulk material andadditives. Bulk material is needed to rebuildthe surface layer and removal of bulkmaterial takes place through a chemicalreaction. These layers are very thin: in therange of tens of nm, see Fig. 3, and thuslow wear rates occur in the mild wearregime.Figure 3: TEM image of the chemical reacted layer ona steel substrate lubricated with ZDDP[1].ObjectiveThe objective of the project is to predict theeffect wear will have on the surface onroughness level (nm). This will be done bycombining the different physical andchemical phenomena on the surface in amulti-physics model.References:[1] Evans R.D. et al., 2005, Transmission ElectronMicroscopy of Boundary-Lubricated Bearing Surfaces.Part 2: Mineral Oil Lubricant with Sulphide andPhosphorus Containing Gear Oil Additives, TribologyTransactions volume 48, 299-307.P-8 Tenth Engineering Mechanics Symposium

Microscopic Mild Wear in the Boundary Lubrication regime

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Microscopic Mild Wear in the Boundary Lubrication regime

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