I. On the electrical resistance of carbon contacts

Bidwell, Shelford

doi:10.1098/rspl.1883.0001

Cited by 8 publications

(1 citation statement)

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“…Bidwell (1883) measured the electrical conductance between crossed cylinders of carbon and bismuth, and Meyer (1898) made some careful measurements of the conductance of steel spheres in contact. Meyer assumed H ertz's equations to hold and deduced th a t the specific resistance of the steel within the area of contact was proportional to the pressure a t th at point.…”

Section: The Area Of Contact Betw Een Stationary Surfacesmentioning

confidence: 99%

The area of contact between stationary and moving surfaces

Bowden

Tabor

1939

Proc. R. Soc. Lond. A

267

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[Plates 25, 26]When two plane surfaces are placed together the area of intimate contact must be very much less than the apparent area. Even if the surfaces are very carefully polished and are made as flat as possible, hills and valleys will still be present on the surface. The upper surface will be supported on these irregularities, and large areas will be separated by a distance which is great compared with the dimensions of a molecule. We do not on May 10, 2018 http://rspa.royalsocietypublishing.org/ Downloaded from 392 F. P. Bowden and D. Tabor know very much about the size of these irregularities nor the degree of flatness of the surfaces. Optical methods cannot reveal irregularities much smaller than half a wave-length of light. The scattering of protons (Knauer and Stern 1929) or the diffraction of electrons (Thomson 1934;Finch, Quarrell and Wilman 1935) can give information about the structure of a small portion of the surface, but these methods would not reveal the presence of isolated peaks nor show how flat are the surfaces over a large area. Since it is difficult, even with the most refined technique, to prepare surfaces which are flat to within one or two thousand angstroms, we may expect th at the area of intimate contact, th a t is, the area over which the surfaces are within the range of the molecular attraction, will, for most surfaces, be very small. Some knowledge of the real area of contact is essential for any complete understanding of the mechanism of friction, and this paper describes an attem pt to estimate this area for both station ary and for moving surfaces. The area of contact betw een stationary surfacesIn 1881 Hertz published his celebrated paper on the elastic deformation of solid surfaces and calculated how the area of contact between curved surfaces should depend upon the load. Bidwell (1883) measured the electrical conductance between crossed cylinders of carbon and bismuth, and Meyer (1898) made some careful measurements of the conductance of steel spheres in contact. Meyer assumed H ertz's equations to hold and deduced th a t the specific resistance of the steel within the area of contact was proportional to the pressure a t th at point. From the work of later investigators it appears th at his surfaces could not hsfve been clean. Further work on the resistance between polished plates was published by Auren (1903) and Browning (1906). The next im portant contribution was made by Binder (1912), who showed th at the conductance was smaller than would be expected if the whole area of the surfaces were touching. He suggested th a t real contact took place only over a small portion of the surface. Experimental verification of these observations was obtained by Pedersen (1916), although the interpretation he gave was different and was based on the assumption of a thin transitional layer of relatively high resistance. Support for Binder's views comes from the work of Holm and his collaborators who have published an exhaustive series of papers from 1922 onwards. Holm shows th a t ...

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Section: The Area Of Contact Betw Een Stationary Surfacesmentioning

confidence: 99%