Journal Home > Volume 11 , Issue 7

The load-bearing behaviour of lubricated contacts depends primarily on the normal force, the relative velocity, and the geometry. Thus, with the aid of the Stribeck curve, it is usually well possible to characterize whether hydrodynamics, mixed friction, or boundary friction is more likely to be present. The fact that the load regime can also depend on the fluid quantity is obvious, but has hardly been systematically investigated so far. Especially for contacts with microscopic roughness, the defined application of a very small amount of fluid is a very challenging requirement. In this paper, a very fundamental study shows how a pin-on-disc tribometer can be used to achieve the transition from dry friction via mixed friction to predominant hydrodynamics by the amount of supplied fluid. The experiments are carried out on samples filed with different coarseness. In addition, the simultaneous influence of partial filling and normal force as well as relative velocity is also shown. Very good reproducibility has been practically reached over the entire range of the tests. Regarding the quantities for the coefficient of friction (COF), it was concluded that close to full filling, a reduction of the fluid quantity has a similar effect on the COF as the reduction of the velocity. This property goes along with the common theory of starved lubricated systems. Such behaviour was not observed to the same extent for the normal force. In the vicinity of smaller fluid quantities, the COF increases very rapidly with further reduction in fluid quantity, far more disproportionately than that with reduction in velocity. With a deeper understanding of this problem, various practical issues such as idling or the run-up process in bearings can also be studied in a more focused manner.


menu
Abstract
Full text
Outline
About this article

On the experimental characterization of the fluid volume influence on the friction between rough surfaces

Show Author's information Lukas STAHLMichael MÜLLER( )Georg-Peter OSTERMEYER
Institute of Dynamics and Vibrations, Technische Universität Braunschweig, Braunschweig 37106, Germany

Abstract

The load-bearing behaviour of lubricated contacts depends primarily on the normal force, the relative velocity, and the geometry. Thus, with the aid of the Stribeck curve, it is usually well possible to characterize whether hydrodynamics, mixed friction, or boundary friction is more likely to be present. The fact that the load regime can also depend on the fluid quantity is obvious, but has hardly been systematically investigated so far. Especially for contacts with microscopic roughness, the defined application of a very small amount of fluid is a very challenging requirement. In this paper, a very fundamental study shows how a pin-on-disc tribometer can be used to achieve the transition from dry friction via mixed friction to predominant hydrodynamics by the amount of supplied fluid. The experiments are carried out on samples filed with different coarseness. In addition, the simultaneous influence of partial filling and normal force as well as relative velocity is also shown. Very good reproducibility has been practically reached over the entire range of the tests. Regarding the quantities for the coefficient of friction (COF), it was concluded that close to full filling, a reduction of the fluid quantity has a similar effect on the COF as the reduction of the velocity. This property goes along with the common theory of starved lubricated systems. Such behaviour was not observed to the same extent for the normal force. In the vicinity of smaller fluid quantities, the COF increases very rapidly with further reduction in fluid quantity, far more disproportionately than that with reduction in velocity. With a deeper understanding of this problem, various practical issues such as idling or the run-up process in bearings can also be studied in a more focused manner.

Keywords: pin-on-disc tribometer, Stribeck curve, starved lubrication, fluid supply, experimental studies

References(18)

[1]
Bhushan B. Introduction to Tribology. Chichester (UK): John Wiley & Sons, 2013.
[2]
Meng Y G, Xu J, Jin Z M, Prakash B, Hu Y Z. A review of recent advances in tribology. Friction 8(2): 221–300 (2020)
[3]
Heshmat H, Pinkus O, Godet M. On a common tribological mechanism between interacting surfaces. Tribol Trans 32(1): 32–41 (1989)
[4]
Heshmat H, Artiles A, Pinkus O. Paper IV(ii) parametric study and optimization of starved thrust bearings. Tribology Series 11: 105–112 (1987)
[5]
Jeng Y R. Theoretical analysis of piston-ring lubrication Part II—Starved lubrication and its application to a complete ring pack. Tribol Trans 35(4): 707–714 (1992)
[6]
Wedeven L D, Evans D, Cameron A. Optical analysis of ball bearing starvation. J Lubr Technol 93(3): 349–361 (1971)
[7]
Heshmat H. Tribology of interface layers. Information on http://site.ebrary.com/lib/academiccompletetitles/home.action, 2010.
DOI
[8]
Czichos H, Habig K H. Tribologie-Handbuch: Tribometrie, Tribomaterialien, Tribotechnik, 3rd edn. Wiesbaden (Germany): Springer Vieweg Wiesbaden, 2010. (in German)
DOI
[9]
Müller M, Ostermeyer G P, Bubser F. A contribution to the modeling of tribological processes under starved lubrication. Tribol Int 64: 135–147 (2013)
[10]
Müller M, Jäschke H, Bubser F, Ostermeyer G P. Simulative studies of tribological interfaces with partially filled gaps. Tribol Int 78: 195–209 (2014)
[11]
Müller M, Völpel A, Ostermeyer G P. On the influence of fluid dynamics and elastic deformations on pressure buildup in partially filled gaps. Tribol Int 105: 345–359 (2017)
[12]
Müller M, Stahl L, Ostermeyer G P. Studies on the pressure buildup and shear flow factors in the cavitation regime. Lubricants 8(8): 82 (2020)
[13]
Müller M, Stahl L, Ostermeyer G P. Experimental studies of lubricant flow and friction in partially filled gaps. Lubricants 6(4): 110 (2018)
[14]
Müller M, Ostermeyer G P. Measurements of partially lubricated contacts on different scales. Proc Appl Math Mech 17(1): 629–630 (2017)
[15]
Ostermeyer G P, Perzborn N. Dynamic friction measurements, especially for high power applications. In: SAE Technical Paper Series, Braunschweig, Germany, 2011: 2011-01-2373.
DOI
[16]
Elrod H G. A general theory for laminar lubrication with Reynolds roughness. J Lubr Technol 101(1): 8–14 (1979)
[17]
Cann P M E, Damiens B, Lubrecht A A. The transition between fully flooded and starved regimes in EHL. Tribol Int 37(10): 859–864 (2004)
[18]
Tong Y, Müller M, Ostermeyer G P. Investigations on the dynamic influence of the contact angle on frictional sliding processes between rough surfaces using NURBS and mortar-based augmented Lagrangian method. Tribol Int 158: 106889 (2021)
Publication history
Copyright
Acknowledgements
Rights and permissions

Publication history

Received: 16 June 2022
Revised: 20 July 2022
Accepted: 03 August 2022
Published: 18 October 2022
Issue date: July 2023

Copyright

© The author(s) 2022.

Acknowledgements

The authors thank the German Research Foundation for funding this project (No. 390252106, "Fundamental Studies on Tribological Contacts with Partially Filled Gaps" ).

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Return