IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Tribology Wednesday Sessions
       Session TR+SS-WeM

Paper TR+SS-WeM5
Combined Nanoindenter and Quartz Crystal Microbalance Studies of Realistic Tribological Contact

Wednesday, October 31, 2001, 9:40 am, Room 132

Session: Fundamentals of Tribology & Adhesion
Presenter: B. Borovsky, North Carolina State University
Authors: B. Borovsky, North Carolina State University
J. Krim, North Carolina State University
S.A.S. Asif, Naval Research Laboratory
K.J. Wahl, Naval Research Laboratory
Correspondent: Click to Email
There has recently been increased interest in studying friction at nanometer and micron length scales at much higher speeds than are obtainable with instruments such as atomic force microscope and surface forces apparatus. Sliding contacts in computer hard drives, micromachines, and many macroscopic applications move at speeds on the order of 1 m/s. This speed regime is routinely accessed by the vibrating surface of a quartz crystal microbalance (QCM). We have therefore constructed a device capable of studying both high-speed sliding friction and contact mechanics by combining a nanoindenting probe and QCM. By measuring normal load, contact stiffness, and QCM response simultaneously, this combination is well-suited to developing the theoretical understanding of probe-QCM systems. In order to establish the relationship between the QCM response and the properties of the interface, we have carried out detailed studies of glass-metal and metal-metal contacts in air. The interfaces are characterized by a contact area (derived from the square of the contact stiffness) proportional to the normal load, consistent with multi-asperity contact and elastoplastic deformation.@footnote 1@ We observe that the frequency shift of the QCM is proportional to the true area of contact as inferred from the contact stiffness. Following an earlier suggestion, we model the interaction in the near-field acoustic regime.@footnote 2@ We find that our results are explained by accounting for the roughness of the opposing surfaces. The magnitude of QCM frequency shift is found to reflect the elasticity of the interface, the number and size of contact regions, and the degree of slippage. Research supported by NSF, AFOSR, and ONR. @FootnoteText@ @footnote 1@ J.A. Greenwood, in Fundamentals of Friction: Macroscopic and Microscopic Processes, NATO ASI Series, I.L. Singer and H.M. Pollock, eds., (Kluwer, Boston, 1992) p. 37. @footnote 2@ A. Laschitsch and D. Johannsmann, J. Appl. Phys. 85, 3759 (1999).