Elasto-hydrodynamic

Chang, L., Deterministic Model for Line-Contact Partial Elasto-Hydrodynamic Lubrication, Tribal. Int., Vol. 28, No. 2,1995,pp. 75-84. 

In gears and ball bearings, extremely high local pressures occur, at least for short periods of time for which the lubricant has no time to flow away from such a high-pressure region. Under these conditions, the above theory of hydrodynamic lubrication would predict a lubrication layer thickness that is smaller than the surface corrugation. However, experiments show that fluid film lubrication still holds under such conditions. To understand this phenomenon, we have to take two effects into account, which lead to elasto-hydrodynamic lubrication ... 

Elasto-Hydrodynamic (EHD) Lubrication in a Rolling-Contact Bearing... 

Corporate Average Fuel Economy CAFE. Requirements necessitated the use of lower viscosity oils, which give improvement in friction (traction) hydrodynamic (HD) and elasto-hydrodynamic lubrication (EHD) full film conditions. 

Interestingly, this slip behaviour of hard-sphere glasses is different in nature from that found earlier by Meeker et al. in jammed systems of emulsion droplets [60]. There, a non-linear elasto-hydrodynamic lubrication model, appropriate for deformable particles, could quantitatively account for their observations. It therefore appears that, while slip is ubiquitous for yield stress fluids flowing along smooth walls, the mechanism for its occurrence can be highly system dependent. 

D. Dowson and G. R. Higginson, Elasto-hydrodynamic Lubrication, Per-gamon Press, Oxford, 1977, Chapter 7. 

As pointed out by Dowson (1), Stanton was aware of the essential features of elasto-hydrodynamic lubrication which may have influenced his decision to use high values of clearance and thus of eccentricity ratio in his tests. In his 1922 report to the Committee he described a series of tests on a steel journal one inch in diameter and three inches long which ran in a phosphor-bronze bush. Pressure was measured through a single hole in the bush which was rotated between successive readings. 

The viscosity of the lubricant at operating temperature and atmospheric pressure was 0.23 so that the calculated value of 0.32 represented an increase due to pressure of some 28 %. Thus evidence of the existence of elasto-hydrodynamic action was provided by this comparatively simple experiment. The separation of the surfaces at the point of nearest approach was calculated to be 0.000054 inch or 1.37 pm. 

OKAMURA, H. (1982), "A Contribution to the Numerical Analysis of Isothermal Elasto Hydrodynamic Lubrication". Proc. "9th Leeds-Lyon Symp. on Tribology", Leeds. 

KOSTREVA, M. M. (1984), "Pressure Spikes and Stability Considerations In Elasto Hydrodynamic Lubrication Models". Trans. ASME JOLT, vol 106 pp 386-397... 

HOUPERT, L. G., B. J. HAMROCK, "A Fast Approach for Calculating Film Thicknesses and Pressures in Elasto Hydrodynamically Lubricated Contacts at High Loads". presented at the ASME/ASLE Joint Lubrication Conference, Atlanta, October 1985. 

LUBRECHT, A. A., W. E. TEN NAPEL, R. BOSMA, "Multigrid, an Alternative Method for Calculating Film Thickness and Pressure Profiles in Elasto Hydrodynamically Lubricated Line Contacts", to appear in Trans. ASME JOT. 

All of the results fall some way below this asymptote, but if the true geometry of the contacting bodies used in this investigation is considered (R /R 13) then the average error is reduced to about 22%. This theoretical overestimation of the Isovlscous-elasto-hydrodynamic film thickness may be contrasted with the findings of Chittenden, Dowson, and Taylor (32) who observed that experimental measurements of film thickness in... 

Ruskell L.E.C., A Rapidly Converging Theoretical Solution of the Elasto hydrodynamic problem for Rectangular Rubber Seals., J. Mech. Eng. Scl., 1980, 22(1). 

Herrebrugh K., Solving the Incompressible and Isothermal Problem in Elasto hydrodynamic Lubrication Through an Integral Equation., Trans. A.S.M.E., J. Lubr. Technol., WD, 1968, 262-270. 

CUDWORTH, C. J. Finite element solution of the elasto-hydrodynamic lubrication of a compliant layer in pure sliding, Proc. 5th Leeds-Lyon Symp. on Tribology, Leeds, 1978, (Inst, of Mech. Engrs, London, 1979), 375-378. 

HEYES, D.M. and MONTROSE, C.J. The use of line and point contacts in determining lubricant rheology under low slip elasto-hydrodynamic conditions, ASME J. Lub. 

An analysis of micro-elasto-hydrodynamic lubrication in synovial joints considering cyclic loading and entraining velocities... 

The current study has provided further confirmation of the major role played by micro-elasto-hydrodynamic lubrication in synovial joints. The model adopted Is still relatively simple and It may be necessary to give further attention to lubricant rheology in order to bring theory and experiment fully Into accord In relation to joint friction. However, the Imposition of fully dynamic conditions has not impaired the essential Indications of quasl-statlc mlcro-elastohydrodynamic analysis of synovial joints reported earlier. 

TRANSIENT MICRO-ELASTO-HYDRODYNAMIC LUBRICATION ANALYSIS... 

The essential problem Is to solve the Integrated Reynolds equation (15) throughout the complete walking cycle for selected loading and motion cycles. In earlier papers (7,8) we considered quasl-statlc conditions In our analysis of micro-elasto-hydrodynamic... 

The reduction In predicted film thickness evident In Figures 13 and 14 for the synovial fluid with a viscosity of only 50 percent of that considered throughout most of the analysis Is neither dramatic nor unexpected. Even with this very small viscosity of 0.005 Pas mlcro-elasto-hydrodynamic action would be expected to ensure fluid-film lubrication in the present model. 

The introduction of surface roughness into Che bearing model has but a small effect upon film thickness prediction under cyclic conditions, but mlcro-elasto-hydrodynamic action effectively smooths out the surface ripples and ensures a fluid-film lubrication mechanism. 

DOWSON, D. and HIGGINSON, G.R. Elasto-hydrodynamic lubrication, Pergamon Press, 1966... 

DOWSON HIGGINSON Elasto-Hydrodynamic Lubrication, SI Edition... 

Dowson, D, Higginson G. R. and Whitaker, A. V., Elasto-hydrodynamic lubrication — a survey of isothermal solutions , J. Mech Engng Sci., 4, 1962,121-126. 

These two observations on the magnitude of the elastic deformations relative to the theoretical film thicknesses and the iso-viscous nature of the lubricants indicate that metal-on-metal joints can theoretically operate in the iso-viscous/elastic regime of elasto-hydrodynamic lubrication. 

The wear achieved from a sliding wear test is in the form of an annulus on the top ball and a worn circle on each of the lower three balls. A standard method of assessing the severity of wear is to measure the wear scar diameters of the lower balls and examine how this varies with increasing load. It can be seen from Figure 5 there was a sudden transformation in the wear regime at the 110 kg load. This is known as the transition region, in which the wear behaviour below is known as mild wear and above as severe wear. When the contact experiences mild wear the oil film between the contacts is intact and mainly elasto-hydrodynamic lubrication is present. When severe wear occurs, the... 

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