SHEAR PROPERTIES OF MOLECULAR LIQUID NEAR A METALLIC WALL

Emanuel DIACONESCU

Vlad – Flaviu ZEGREAN

zegrean@fim.usv.ro

Marilena GLOVNEA

Department of Applied Mechanics, University “Stefan cel Mare” of Suceava, ROMANIA

Abstract. Although the thickness of EHD oil films should vanish at very low rolling speeds, experimental investigations indicate that often this thickness does not fall below a remnant value of 10-30 nm. Initially, this phenomenon was attributed to a much higher viscosity near the wall than in the bulk, according to an empirical formula. Recently, theoretical physical background of the phenomenon was advanced by means of molecule-wall interaction potential. It was shown that, besides viscosity, shear modulus and limiting shear stress are enhanced in the neighborhood of the wall. These theoretical findings predict correctly experimentally found thin film thickness. New experimental evidence is needed to support theoretical results. This paper provides experimental results concerning the evaluation of structural flow units, minimum intermolecular potential and limiting shear stress in thin layers.
 

Keywords: liquid-wall interaction, viscosity, shear modulus, limiting shear stress, molecular layer

References

1. Jonhson G.J., Wayte R., Spikes H.A., 1991, “The Measurement and Study of Very Thin Lubricant Films in Concentrated Contact,” Tribology Transactions, 34, (2), pp. 187-194.

2. Cann, P.M., Spikes, H.A., 1994, “Thin Film Optical Interferometry in the Study of Grease Lubrication in a Rolling Point Contact,” Acta Tribologica, 2 (1), pp. 45-50, (1994).

3. Luo, J. B., Wen, S. Z., 1996, “Mechanism and Characteristics of Thin Film Lubrication at Nanometer Scale,” Science in China (A), Vol. 39 (12), pp. 1312-1322.

4. Zhang, C., Luo, J., Wen, S., 2001, “A New Postulation of Viscosity and its Application in Computation of Film Thickness in Thin Film EHL,” Acta Tribologica, 9 (1), pp. 35-40.

5. Zhang, C., Luo, J., Wen, S., 2002, “A New Postulation of Viscosity and its Application in Computation of Film Thickness in TFL,” ASME Journal of Tribology, 124, pp. 811-814.

6. Diaconescu, E.N., 2006, “Nanometric Thickness EHL Oil Films,” Proceedings of IJTC, STLE/ASME International Joint Tribology Conference, San Antonio, Texas, USA, October 22-25.

7. Diaconescu, E. N., 2007, “A Physical Approach to the Wall Effect in Elastohydrodynamic Lubrication,” ROTRIB 2007.

8. Diaconescu, E.N., 2004, “Solid-like Properties of Molecular Liquids Subjected to EHD Conditions,” ASME/STLE International Joint Tribology Conference, October 24-27, Long Beach, California, USA, 10 pp. on CD.

9. Hirst, W., Moore, A. J., 1981, “The Effect of Temperature on Traction in Elastohydrodynamic Lubrication,” Phil. Trans. of Roy. Soc. London, vol. 298, A 1438, pp. 183-298.