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Slip length of the tribo system steel-polyalphaolefin-steel determined by a novel tribometer
Tobias Corneli, Technische Universität Darmstadt, Institute for Fluid Systems, Germany
Peter Pelz, Technische Universität Darmstadt, Institute for Fluid Systems
Gerhard Ludwig, Technische Universität Darmstadt, Institute for Fluid Systems
Nowadays sealing systems are commonly designed by means of hydrodynamic and elastohydrodynamic theories. Although the analytical as well as the computational approaches have improved in meaning full manner since the last decades: For small sealing gaps, in the order of micrometers and below, a discrepancy between experimental investigated and theoretically predicted leakage flows occur. As a cause for the discrepancy a breakdown of the no slip boundary condition is suspected. Since in small sealing gaps the continuum hypothesis is violated and molecular effects have to be considered. One fundamental quantity to take molecular affects into account is the slip length.
Within this paper a new measurement apparatus to evaluate the slip length for hydraulic applications is presented. The adjustable gaps between two planar surfaces are in the order of magnitude of 1 ?m. In a first step the slip length for the system steel-oil steel is investigated at three different temperatures: 18 °C,22 °C and 25 °C. The measured slip lengths are in the order of magnitude of ~100 nm.