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Isothermal Elastohydrodynamic Lubrication of Point Contacts: Part III—Fully Flooded Results
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1977
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Tribological CoatingEngineeringFluid MechanicsMechanical EngineeringSurface TechnologyMechanicsContact MechanicRheologyThermodynamicsThin Film ProcessingPoint ContactsMaterials ScienceHydrodynamic LubricationEllipticity ParameterSolid MechanicsTribological PropertyMechanical PropertiesFilm ThicknessMaterials CharacterizationApplied PhysicsThin FilmsMinimum Film ThicknessTribocorrosionMechanics Of Materials
The study extends prior theory to investigate how ellipticity, speed, load, and material parameters influence minimum film thickness in point contacts. The authors varied ellipticity from 1 to 8, speed over two orders of magnitude, load over one order, and considered bronze, steel, and silicon nitride solids with paraffinic and naphthenic oils to derive the exponent in the dimensionless material parameter. Thirty‑four cases produced a minimum‑film‑thickness formula H¯min = 3.63 U^0.68 G^0.49 W^−0.073(1 − e^−0.68k) with k ≈ 1.03(Ry/Rx)^0.64, and contour plots show pressure spikes and side lobes; these theoretical predictions agree with experimental interferometry data.
Utilizing the theory developed by the authors in an earlier publication, the influence of the ellipticity parameter, the dimensionless speed, load, and material parameters on minimum film thickness was investigated. The ellipticity parameter was varied from one (a ball on a plate configuration) to eight (a configuration approaching a line contact). The dimensionless speed parameter was varied over a range of nearly two orders of magnitude. The dimensionless load parameter was varied over a range of one order of magnitude. Conditions corresponding to the use of solid materials of bronze, steel, and silicon nitride and lubricants of paraffinic and naphthenic mineral oils were considered in obtaining the exponent in the dimensionless material parameter. Thirty-four different cases were used in obtaining the minimum film thickness formula given below as H¯min=3.63U0.68G0.49W−0.073(1−e−0.68k) A simplified expression for the ellipticity parameter was found where k=1.03RyRx0.64 Contour plots were also shown which indicate in detail the pressure spike and two side lobes in which the minimum film thickness occurs. These theoretical solutions of film thickness have all the essential features of the previously reported experimental observations based upon optical interferometry.