A model is developed to study the tribological behavior of sliding micro-contacts. It provides a building block to the modeling of tribo-contacts in boundary lubrication. Three contact variables are calculated at the asperity-level by relating them to the state of contact and the state of asperity deformation. These variables include micro-contact friction force, load carrying capacity and flash temperature. The deformation of the contacting asperity is either elastic, elasto-plastic, or fully plastic. Furthermore, the asperity may be covered by the lubricant/additive molecules adsorbed on the surface, protected by a surface oxide layer or other chemical reaction films, or in direct contact with no boundary protection. The possibility of the contact in each of these three states is represented by a corresponding contact probability. A numerical method is developed to determine the contact state and contact variables in the course of an asperity-to-asperity collision. The asperity flash temperature, which governs the kinetics of lubricant/surface adsorption/desorption, is first calculated by integrating the Jaeger equation over the contact area and in time. Then, the probability of contact covered by an adsorbed film is determined using the Volmer adsorption isotherm, and the probability of contact protected by the oxide layer is estimated using a classical wear theory. For elastic/elasto-plastic deformation of the asperity, the friction coefficient is given by the linear combination of the friction coefficients of the three contact states with their contact probabilities as the weighting factors. For fully plastic deformation of the asperity, the contact pressure and friction force become dependent of each other. The shear stress is approximated by a linear function of the contact probabilities, and the contact pressure and friction coefficient then calculated. Meanwhile, the influence of fresh surface generation due to plastic flow on the contact probabilities is also modeled. Insights are provided into the asperity collision through numerical studies of a sample problem. In addition, parametric studies are carried out to analyze the effects of lubricant and surface parameters on the micro-contact severity and its load capacity.
Skip Nav Destination
Article navigation
January 2003
Technical Papers
A Micro-Contact Model for Boundary Lubrication With Lubricant/Surface Physiochemistry
H. Zhang,
H. Zhang
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802
Search for other works by this author on:
L. Chang,
L. Chang
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802
Search for other works by this author on:
M. N. Webster,
M. N. Webster
Corporate Strategic Research, ExxonMobil Research and Engineering Company, Annandale, NJ 08801
Search for other works by this author on:
A. Jackson
A. Jackson
Corporate Strategic Research, ExxonMobil Research and Engineering Company, Annandale, NJ 08801
Search for other works by this author on:
H. Zhang
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802
L. Chang
Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802
M. N. Webster
Corporate Strategic Research, ExxonMobil Research and Engineering Company, Annandale, NJ 08801
A. Jackson
Corporate Strategic Research, ExxonMobil Research and Engineering Company, Annandale, NJ 08801
Contributed by the Tribology Division of the American Society of Mechanical Engineers for presentation at the ASME/STLE Tribology Conference, Cancun, Mexico October 27–30, 2002. Manuscript received by the Tribology Division September 18, 2001 revised manuscript received February 20, 2002. Associate Editor: J. A. Williams.
J. Tribol. Jan 2003, 125(1): 8-15 (8 pages)
Published Online: December 31, 2002
Article history
Received:
September 18, 2001
Revised:
February 20, 2002
Online:
December 31, 2002
Citation
Zhang , H., Chang, L., Webster , M. N., and Jackson, A. (December 31, 2002). "A Micro-Contact Model for Boundary Lubrication With Lubricant/Surface Physiochemistry ." ASME. J. Tribol. January 2003; 125(1): 8–15. https://doi.org/10.1115/1.1481365
Download citation file:
Get Email Alerts
Related Articles
Refined Friction Modeling for Simple Upsetting
J. Manuf. Sci. Eng (November,1997)
Tribological Investigations of Two-Dimensional Nanostructured Lamellar Materials as Additives to Castor-Oil-Derived Lithium Grease
J. Tribol (September,2022)
Characterization of Pelletized MoS 2 Powder Particle Detachment Process
J. Tribol (July,2001)
Related Proceedings Papers
Related Chapters
On the Evaluation of Thermal and Mechanical Factors in Low-Speed Sliding
Tribology of Mechanical Systems: A Guide to Present and Future Technologies
Contact Laws
Contact in Structural Mechanics: A Weighted Residual Approach
Materials
Design and Application of the Worm Gear