Experimental Study on the Physics of Thick EHL Film Formation with Grease at Low Speeds

Abstract

An unexpected behavior of grease in rolling contact has become known among tribologists that it forms thick film at low speeds, but the nature of the film has still been in dispute. The dominance of EHL effects has been demonstrated in the previous works, in which the increase in the generalized viscosity of grease has been reasoned to cause the increase in the film thickness. This paper describes experiments to measure the film thickness with optical interferometry, to observe the flow in and around the contact with microscopy, and to determine the change in the concentration of the thickener by IR spectroscopy. On the basis of these findings, the physics of the thick film formation with grease at low speeds is discussed.

This is a preview of subscription content, log in to check access.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10

References

  1. 1.

    Aihara, S., Dowson, D.: A study of film thickness in grease lubricated elasto-hydrodynamic contacts. In: Proceedings of the 5th Leeds-Lyon Symposium on Tribology, Elastohydrodynamics and Related Topics, pp. 105–115. Mechanical Engineering Publications, London (1978)

  2. 2.

    Kimura, Y., Endo, T., Dong, D.: EHL with grease at low speeds. In: Advanced Tribology, Proceedings of CIST2008 & ITS-IFToMM2008, pp. 15–19. Springer, Berlin (2010)

  3. 3.

    Dong, D., Endo, T., Kimura, Y.: Formation of thick EHL film with grease at low speeds. In: Proceedings of the 4th World Tribology Congress, Kyoto, p. 818 (2009)

  4. 4.

    Hurley, S., Cann, P.M.: IR spectroscopic analysis of grease lubricant films in rolling contacts. In: Lubrication at the Frontier, The Role of the Interface and Surface Layers in the Thin Film and Boundary Regime, Proceedings of the 25th Leeds-Lyon Symposium on Tribology. Elsevier Tribology Series, vol. 36, pp. 589–600. Elsevier, Amsterdam (1998)

    Google Scholar 

  5. 5.

    Kaneta, M., Ogata, T., Takubo, Y., Naka, M.: Effect of a thickener structure on grease elastohydrodynamic lubrication films. Proc. Inst. Mech. Eng. Part J 214(4), 327–336 (2000)

    Article  Google Scholar 

  6. 6.

    Cen, H., Lugt, P.M., Morales-Espejel, G.: On the film thickness of grease-lubricated contacts at low speeds. Tribol. Trans. 57(4), 668–678 (2014)

    CAS  Article  Google Scholar 

  7. 7.

    Yoshinari, T., Namiki, M.: Main rotor bearing grease for wind turbine based on the new design concept. NLGI Spokesm. 76(6), 22–29 (2013)

    Google Scholar 

  8. 8.

    Nakajima, S., Izaki, K., Takemura, K., Kimura, Y., Cann, P.M.: Development of new urea grease for steel continuous casting machine under boundary lubrication. NLGI Spokesm. 68(8), 8–16 (2004)

    CAS  Google Scholar 

  9. 9.

    Spikes, H.A., Cann, P.M.: The development and application of the spacer layer imaging method for measuring lubricant film thickness. Proc. Inst. Mech. Eng. Part J 215(3), 261–277 (2001)

    Article  Google Scholar 

  10. 10.

    Wada, S., Tsukijihara, M., Hara, H.: Elastohydrodynamic lubrication between two heavily loaded cylinders lubricated by a Bngham solid. Bull. JSME 22(167), 871–876 (1979)

    Article  Google Scholar 

  11. 11.

    Yang, Z., Qian, X.: A solution to the grease lubricated EHD thickness in an elliptical contact. In: Tribology—Friction, Lubrication and Wear, Fifty Years On, Proceedings of the IMechE International Conference, vol. 1, pp. 97–104. Mechanical Engineering Publications, London (1987)

  12. 12.

    Kauzlarich, J.J., Greenwood, J.A.: Elastohydrodynamic lubrication with Herschel-Bulkley model greases. ASLE Trans. 15(4), 269–277 (1972)

    CAS  Article  Google Scholar 

  13. 13.

    Jonkisz, W., Krzeminski-Freda, H.: Pressure distribution and shape of an elastohydrodynamic grease film. Wear 55(1), 81–89 (1979)

    Article  Google Scholar 

  14. 14.

    Dong, D., Qian, X.: A theory of elastohydrodynamic grease-lubricated line contact based on a refined rheological model. Tribol. Int. 21(5), 261–267 (1988)

    Article  Google Scholar 

  15. 15.

    Palacios, J.M., Palacios, M.P.: Rheological properties of greases in EHD contacts. Tribol. Int. 17(3), 167–171 (1984)

    CAS  Article  Google Scholar 

  16. 16.

    Dong, D., Kimura, Y., Okada, K., Liu, W.: Grease lubrication in isothermo-elastohydrodynamic line contact. Lubr. Sci. 8(3), 253–267 (1996)

    CAS  Article  Google Scholar 

  17. 17.

    Bair, S.: The shear rheology of thin compressed liquid films. Proc. Inst. Mech. Eng. Part J 216(1), 1–17 (2002)

    CAS  Article  Google Scholar 

  18. 18.

    Tanaka, S., Sengoku, K., Kyogoku, K., Nakahara, T.: Measurement of distribution of thickener concentration in grease film in EHL point contact. In: Proceedings of JAST Tribology Conference, October 2002, Sendai, pp. 405–406 (2002) (in Japanese)

  19. 19.

    Hoshi, K., Takiwatari, K., Nanao, H., Yashiro, H., Mori, S.: In situ observation of EHL films of greases by a micro infrared spectroscopy. J. Jpn. Soc. Tribol. 60(2), 153–159 (2015). (in Japanese)

    CAS  Google Scholar 

  20. 20.

    Kochi, T., Ichimura, R., Yoshihara, M., Dong, D., Kimura, Y.: Film thickness and traction in soft EHL with grease. Tribol. Online 12(4), 171–176 (2017)

    Article  Google Scholar 

  21. 21.

    McNaught, A.D., Wilkinson, A.: IUPAC compendium of chemical terminology, 2nd edn. Blackwell, Oxford (1997)

    Google Scholar 

  22. 22.

    Noda, T., Liu, Y., Aramaki, H., Wang, Q.J.: Elastohydrodynamic simulation of grease lubrication, 613. In: The 5th World Tribology Congress, Torino (2013)

  23. 23.

    Sisko, A.W.: The flow of lubricating grease. Ind. Eng. Chem. 50(12), 1789–1792 (1958)

    CAS  Article  Google Scholar 

Download references

Author information

Affiliations

Authors

Corresponding author

Correspondence to Takashi Nogi.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Appendix

Appendix

The Carreau–Yasuda viscosity equation

$$\eta^{*} = (\mu_{1} - \mu_{2} )(1 + (\lambda \dot{\gamma })^{a} )^{(n - 1)/a} + \mu_{2}$$
(3)

is an empirical equation being used for describing non-Newtonian rheology of polymer melts or polymer solutions. It gives a generalized viscosity η* as a function of the shear rate \(\dot{\gamma }\) such that a transition occurs from the first, high Newtonian viscosity μ1 at low shear rates to the second, low Newtonian viscosity μ2 at high shear rates. The three parameters are used to characterize the transition: it occurs at lower shear rate for larger λ, becomes smoother for smaller a and more gradual for smaller n. No means exist to give a priori the values of these parameters, and they were hypothesized through rheometry of the sample greases.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Kochi, T., Sakai, M., Nogi, T. et al. Experimental Study on the Physics of Thick EHL Film Formation with Grease at Low Speeds. Tribol Lett 67, 55 (2019). https://doi.org/10.1007/s11249-019-1166-7

Download citation

Keywords

  • Elastohydrodynamic lubrication
  • Grease
  • Film thickness
  • Low speed