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1 2010

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Tribological systems of surfaces with frictional resistance reduction

Wierzcholski K., Miszczak A.

Journal of KONES

2010

Vol. 17, No. 3

491-496

In this paper are assumed micro-ridges and micro-grooves on the Journal and bearing sleeve surfaces. Friction on the boundary layer of the body moving in the oil at high Reynolds numbers may be decreased due to such asculpturing of the surface. The grooved scale of the shark skin is an example of such tribological systems. There size ranges of the grooves are from 200 jum to 400/jm. The surface of the each scale contains parallel groove between so-called ribbed directed almost parallel to the longitudinal body axis. An explanation of the shark skin effect has been proposed recently for the micro-bearing surfaces shapes execution. In the boundary layer, not only longitudinal micro-turbulence but also cross-directed micro-turbulence occurs. The longitudinal grooves of the shark and bearing surface prevent the appearance of the cross-directed micro-turbulences. Forces of the streaming oil in bearing or micro-bearing gap act on the bearing surface in two different ways. On one side, the oil generates the pressure directed normally to the surface of the Journal surface and is responsible for inertiaforces. On the other side, friction or shearing force acts tangentially to the bearing surface. The resulting force depends on the geometry of the body, its relative dimensions to the oilflow and on such characteristics of the oil as its density, viscosity and velocity.