Minimum Film Thicknesses in Lubricated Point Contacts Operating in the Elastic Piezoviscous Regime

Abstract

Previous attempts to derive equations for the minimumfilm thickness in the elastic piezmiscous regime have relied upon extrapolations fiom numerical results. This paper describes an alternative approach in which the characteristics of heavily loaded contacts are exploited to obtain general expressions,$rstly, for the central region and secondly, for the side lobes that may form at the ends of the contact. It is shown that the clearances in these two regions behave differently.The elastic piezoviscous regime must, therdore, be divided into two sub-regimes. Expressions for minimum clearance are presented for each.

Film thickness prediction in elastohydrodynamically lubricated elliptical contacts

“…The curve fit chosen in this paper does not use an exponential function as Hamrock and Dowson [3], Chittenden et al [5], Hooke [6] or Nijenbanning et al …”

“…Several researchers have presented predictive formulae for the film thickness in line and circular contacts based on simplified analyses for asymptotic cases and/or curve fits of numerical solutions [1, 2]. Also, for the more general case of wide elliptical contacts, such formula have been presented [3][4][5][6]. However, a major problem is that these are either based on an extension of a circular contact formula or on curve-fitting of numerical results in a rather narrow range of load conditions and ellipticity values.…”

The determination of the pressure—viscosity coefficient of a lubricant through an accurate film thickness formula and accurate film thickness measurements

“…The behaviour of the minimum film thickness in elliptical contacts is even more complex than for the central film thickness. The location of the minimum film thickness may occur at the centre line, or at the side lobes, see Moes [3], Venner [8] and Hooke [13]. Chaomleffel et al [12] use the central film thickness formula by Nijenbanning et al [9] as a basis, and apply a correction table…”

“…(4) Archard and Cowking [21] for circular hard contacts (5) Evans and Snidle [19], for circular contacts (6) Hooke [13] for arbitrary elliptical contacts (7) Sutcliffe [22] for long elliptical contacts (8) Greenwood [23] for circular contacts (note that this model was not suggested by Greenwood) From the Moes family: (9) Venner [8] for circular contacts (10) Nijenbanning, Venner and Moes [9] for circular and short elliptical contacts (11) Venner and Lubrecht [10] for circular contacts, and (12) Moes [3] for arbitrary elliptical contacts Figure 1 illustrates the large differences in the values of some of these formulas for L = 10. The proper choice of a good approximation formula is important, as roughly seen nondimensional film thickness H  L 1/23/4 so   h 4/32 .…”

Analytical Formula for the Ratio of Central to Minimum Film Thickness in a Circular EHL Contact

“…Since the pioneering work of Hamrock-Dowson in 1977 [1], numerous prediction formulas have been published in the literature [2][3][4][5][6]. An overview of the prediction formulas can be found in References [7][8][9].…”