The author is to be commended for his attempt to cope analytically with the complex problem of friction. A few comments regarding the present paper are in place. The present simplified friction model is essentially based on the 1949 Mindlin approach (see Ref. 1). According to this concept, it is assumed that the contact area of an elastic spherical asperity is given by the frictionless Hertz solution (see Eq. (2)) and that slip of such an asperity will ensue when the average shear stress at its contact area reaches a critical value (see Eq. (6)). These simplifying assumptions may lead to some unrealistic situations where the local equivalent von Mises stress in the contact interface can exceed the yield strength of the sphere material. Additional shortcomings of the Mindlin concept is that an increase of the contact area due to the tangential load is completely excluded, and that sliding inception always occurs in the contact interface of each asperity regardless of its level of normal loading. This would contradict the well known phenomena of junction growth and material transfer, where the latter requires slip below the contact interface. In this regard, it is worthwhile mentioning a different approach to sliding inception of a single spherical asperity (2) and to modeling of static friction of contacting rough surfaces 3. These papers are not limited to elastically deformed asperities, and in Ref. 3 adhesion effect was also considered. However, these two models still assume, like in the present paper, that the contact area resulting from a frictionless normal loading is unaffected by the additional tangential load. A more realistic model was recently presented in two papers by Brizmer et al. assuming full stick contact condition for both normal and tangential loadings (see Refs. 4,5). The full stick contact condition captures very well the concept of an adhesive joint formed in the contact interface. It does not require simplifying assumptions regarding the size of the contact area and the location of slip at the contact interface; therefore, it never violates the von Mises yield criterion. Furthermore, it utilizes first principles to predict the sliding inception at the instant of vanishing tangential stiffness (as shown in Fig. 1 of the present paper) and to obtain the resulting corresponding static friction and junction growth. Since the full stick contact condition does not impose slip at the contact interface, it allows for the possibility of material transfer under severe normal loads. Additionally, the results of Refs. 4,5 correlate well with some preliminary experimental results obtained by Ovcharenko et al. (6).
Skip Nav Destination
e-mail: etsion@technion.ac.il
Article navigation
Discussions
Discussion: “A Greenwood–Williamson Model of Small-Scale Friction” (Jones, R. E., 2007, ASME J. Appl. Mech., 74, pp. 31–40)
Izhak Etsion
e-mail: etsion@technion.ac.il
Izhak Etsion
Fellow ASME
Department of Mechanical Engineering
, Technion, Haifa 32000, Israel
Search for other works by this author on:
Izhak Etsion
Fellow ASME
Department of Mechanical Engineering
, Technion, Haifa 32000, Israele-mail: etsion@technion.ac.il
J. Appl. Mech. Jul 2008, 75(4): 045501 (1 pages)
Published Online: May 15, 2008
Article history
Received:
April 9, 2007
Revised:
September 24, 2007
Published:
May 15, 2008
Article
Article discussed|
View article
Citation
Etsion, I. (May 15, 2008). "Discussion: “A Greenwood–Williamson Model of Small-Scale Friction” (Jones, R. E., 2007, ASME J. Appl. Mech., 74, pp. 31–40)." ASME. J. Appl. Mech. July 2008; 75(4): 045501. https://doi.org/10.1115/1.2870267
Download citation file:
Get Email Alerts
Cited By
Radial Deflection of Ring-Stiffened Cylinders Under Hydrostatic Pressure
J. Appl. Mech (December 2024)
Related Articles
A New Mechanism of Asperity Flattening in Sliding Contact—The Role of Tool Elastic Microwedge
J. Tribol (October,2003)
Solution of the Contact Zone Orientation for Normal Elliptical Hertzian Contact
J. Appl. Mech (May,2011)
A Mechanics Approach to Static Friction of Elastic–Plastic Fractal Surfaces
J. Tribol (April,2005)
Scale Effect in Dry Friction During Multiple-Asperity Contact
J. Tribol (January,2005)
Related Proceedings Papers
Related Chapters
Numerical Test Research on the Shear Strength Parameters of Rock Joints Based on the Fractal Theory
Geological Engineering: Proceedings of the 1 st International Conference (ICGE 2007)
Study on Probability Distribution of Shear Strength Parameters of Sliding Zone in Three Gorges Reservoir Zone Based on Multiple Test Methods
Geological Engineering: Proceedings of the 1 st International Conference (ICGE 2007)
Quantitative Study on the Shear Strength Parameter of Undisturbed Loess
Geological Engineering: Proceedings of the 1 st International Conference (ICGE 2007)