Elastohydrodynamic Lubrication of Finite Line Contacts

In this paper, a numerical solution to the elastohydrodynamic lubrication (EHL) problem is presented for a cylindrical roller with axially profiled ends, rolling over a flat plane. Convergence was obtained for moderate load and material parameters (glass, steel, and a mineral oil). Isobars, contours, and section graphs, show pressure variation and film shape. Predictions of film thickness compare favorably with experiments which use the optical interference method, as well as with other theoretical results for an infinite line contact, or an ellipse having a long slender aspect ratio. The maximum EHL pressure occurs near the start of the profiling and can exceed pressure concentrations there predicted by elastostatic theory.

Depletion and Retention of Fluid on a Rotating Disk

Assuming that a dry circular center is present at which the contact angle between the liquid and solid phases remains constant at all times, the axisymmetric free surface of liquid on a flat disk is determined from the Laplace formula in which the radial gradient of the fluid pressure balances the centrifugal force. The depletion of a thin layer of fluid from a rotating finite disk is described quasi-statically. A remnant of residual fluid is determined to remain on the disk. For moderate rotating speed, this remnant fluid volume is retained on the disk without loss.

Surface Topography Changes in Polymer-Metal Sliding—II

The variation in the surface topographical parameters for the case of sliding between high density polyethylene and poly(vinyl chloride) pin ends and a steel disk periphery was investigated. Sliding surface profile ordinate data were obtained at 2μm intervals using a data acquisition system, both along and perpendicular to the direction of sliding. A number of surface roughness parameters, viz., the r.m.s. and c.l.a. roughness, the slope, density, and radius of curvature of asperities, the standard deviation and distribution of profile ordinates, slopes, radii of curvatures and heights of asperities were calculated using a Fortran IV computer program. The analysis showed that the surface parameters undergo a marked variation during the early part of sliding, but the variation is statistically insignificant during the later part. It was found that the standard deviation of peak heights can be approximated by the r.m.s. surface roughness.

Investigation of Friction and Wear of Dynamically Loaded Hydrodynamic Bearings With Abrasive Contaminants

A test system is described for investigating friction and wear of hydrodynamic bearings under cyclical dynamic loading conditions with contaminant abrasive particles in the oil supply. Dynamic loading on the test bearing is synchronized with the shaft rotation, so that the oil film thickness history can be determined from the measured shaft orbit for any point on the shaft and liner periphery. Either clean or contaminated oil can be supplied to the test bearing from two separate oil supply systems. Experimental results obtained for six shaft/liner bearing material combinations were similar to those previously obtained for static loading. The friction and wear behavior were found to depend on the relative hardnesses of the shaft and liner. A larger shaft-to-liner hardness ratio generally resulted in more shaft wear and less liner wear. This is attributed to an increased tendency for abrasive particles to partially embed in the liner and cut the shaft when the shaft is harder and/or the liner is softer. With partial embedding, high bearing friction indicative of continuing abrasion persists after changing from contaminated to clean oil.

Stability of Unsymmetrical Rigid Rotor Supported by Self-Acting Gas-Lubricated Journal Bearings

In order to determine the threshold of instability for an unsymmetrical rigid rotor supported by two identical self-acting, plain-cylindrical gas journal bearings, a theoretical approach is made by the use of the quasi-static nonliner PH method. Influence of various parameters affecting the threshold of instability of the unsymmetrical rotor is experimentally shown and compared with the theoretical results. The experimental variables considered in this paper include bearing load, bearing length, bearing clearance, the axial deviation of the center of gravity from the center of the rotor span. Good agreement was obtained between the experimental and theoretical results.