A Theoretical Analysis of the Mixed Elastohydrodynamic Lubrication in Elliptical Contacts With an Arbitrary Entrainment Angle

Abstract

Numerical simulations of the elastohydrodynamic lubrication (EHL) have been conducted by many researchers, in which the entrainment velocity is usually parallel to one of the axes of Hertzian contact ellipse. However, in some engineering applications, such as the counterformal contacts in spiral bevel and hypoid gears, entraining velocity vector may have an oblique angle that could possibly influence the lubrication characteristics significantly. Also, a vast majority of gears operate in mixed EHL mode in which the rough surface asperity contacts and lubricant films coexist. These gears are key elements widely used for transmitting significant power in various types of vehicles and engineering machinery. Therefore, model development for the mixed EHL in elliptical contacts with an arbitrary entrainment angle is of great importance. In the present paper, a recently developed mixed EHL model is modified to consider the effect of arbitrary entraining velocity angle, and the model is validated by comparing its results with available experimental data and previous numerical analyses found in literature. Based on this, numerical simulations are conducted to systematically study the influence of entrainment angle on lubricant film thickness in wide ranges of speed, load, and contact ellipticity. The obtained results cover the entire lubrication spectrum from thick-film and thin-film lubrication all the way down to mixed and boundary lubrication. In addition, minimum film thickness prediction formula is also developed through curve-fitting of the numerical results.

Study on geometric contact model of elastohydrodynamic lubrication of arbitrary intersecting line gear

“…As found in Table , the circular sections designed by the previous method, as shown in Figure B, have large radii ratio of the long and short axes a * / b * , which values in examples both exceed 9. According to Chittenden et al and Pu et al, if the direction of entertainment speed U s coincides with the short axis of contact ellipse b * , it is conducive to EHL. However, if the direction of entertainment speed U s deviates from the short axis of contact ellipse b * , the greater the deviation angle, the smaller the thickness of the central oil film and the minimum oil film thickness.…”

“…Hamrock and Dowson analysed the influence of the ellipticity on the pressure distribution and the oil film shape . Chittenden et al and Pu et al studied the EHL in elliptical contacts with an arbitrary entrainment angle. Wen shows that EHL point contact depends on the elliptical contact area.…”

Microstress cycle and contact fatigue of spiral bevel gears by rolling-sliding of asperity contact

“…Similar combinations of fatigue model and mixed EHL were also applied by Li and Kahraman [28], Li and Anisetti [29], et al Modifications to the mixed EHL model have been attempted in Refs. [30] and [31] to simulate the mixed EHL elliptical contacts with arbitrary velocity vectors by considering the effect of 3D roughness. These modified models laid the foundation for the later lubrication analysis in spiral bevel gears and hypoid gears by Pu et al [32] and Cao et al [8].…”

A simple deterministic plastoelastohydrodynamic lubrication (PEHL) model in mixed lubrication

“…This ensures diagonal dominance under all conditions of operation. The unified approach was first presented by Hu and Zhu [11] and later improved to consider the effect of differential scheme and mesh density [23], the treatment of roughness derivatives [24], the effect of viscosity model [25], the agreement of the model output with the dry contact results [26], effect of finite geometry [27] and the ability to handle arbitrary entrainment speeds [28]. Later, Holmes et al [29] used the unified approach to develop a mixed lubrication solver based upon the differential deflection method.…”