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Effect of lubricant molecular rheology on formation and shear of ultra-thin surface films

journal contribution
posted on 14.10.2013, 08:14 by W.W.F. Chong, M. Teodorescu, Homer Rahnejat
The physics of molecularly thin fluid films formed between surface features at close range is investigated. It is found that the interplay between discrete lubricant drainage from such contacts and localized contact deflection plays an important role both on the load carrying capacity of these asperity level conjunctions as well as on friction. Small spherical molecules tend to solvate near assumed smooth surfaces of asperities at nano-scale. Their discrete drainage at steadily decreasing gaps adds to the viscous friction of any bulk lubricant film. However, at the same time the generated solvation pressures increase the load carrying capacity. Conversely, long chain molecules tend to inhibit solvation, thus showing a decrease in the load carrying capacity, whilst through their wetting action reduce friction. Consequently, real lubricants should comprise molecular species which promote desired contact characteristics, as indeed is the case for most base lubricants with surmised properties of certain additives. The methodology presented underpins the rather empirical implied action of surface adhered films. This is an initial approach which must be expanded to fluids with a more complex mix of species. If applicable, this could also be an alternative (potentially time saving) approach to Monte Carlo simulations for molecular dynamics.

Funding

The authors acknowledge the technical support from partners and sponsorship provided by the EPSRC through the ENCYCLOPAEDIC program grant.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Citation

CHONG, W.W.F., TEODORESCU, M. and RAHNEJAT, H., 2001. Effect of lubricant molecular rheology on formation and shear of ultra-thin surface films. Journal of Physics D - Applied Physics, 44 (165302), 11pp.

Publisher

© IOP Publishing

Version

NA (Not Applicable or Unknown)

Publication date

2011

Notes

This article is closed access.

ISSN

0022-3727

Language

en

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