Some Insights Into Micro-EHL Pressures

N. Fang, L. Chang

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


An analytical model is developed in this paper which relates the major component of micro-EHL pressure responses to lubricant properties, roughness geometry, contact load, velocity, and slide-to-roll ratio. Analyses are then conducted showing the effects of system parameters on this micro-EHL pressure. For a Newtonian lubricant with an exponential pressure-viscosity law, this pressure would be large unless the contact practically operates right at pure rolling. The magnitude of the pressure rippling is largely independent of the slide-to-roll ratio, and smaller wavelength components of the surface roughness generate larger micro-EHL pressures. With less dramatic pressure-viscosity enhancement such as the two-slope model, the micro- EHL pressure is generally smaller and sensitive to the slide-to-roll ratio, larger with higher sliding in the contact. Furthermore, this pressure-viscosity model yields a micro-EHL pressure that becomes vanishingly small corresponding to sufficiently small wavelength components of the roughness. For a shear-thinning non-Newtonian lubricant, such as the Eyring model, with an exponential pressure-viscosity law, substantially less micro-EHL pressure rippling is generally developed than its Newtonian counterpart. While the pressure rippling is insensitive of the slide-to-roll ratio like its Newtonian counterpart, it vanishes corresponding to sufficiently small wavelength components of the roughness. The analyses revealed that a key factor resulting in a smaller micro-EHL pressure with the two-slope model or the Eyring model is the lower viscosity or shear-thinned effective viscosity in the loaded region of the contact. Since EHL traction is proportional to this viscosity, contacts lubricated with oils exhibiting higher traction behavior would develop larger micro-EHL pressures and thus would be more vulnerable to fatigue failure.

Original languageEnglish (US)
Pages (from-to)473-480
Number of pages8
JournalJournal of Tribology
Issue number3
StatePublished - Jul 1999

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films


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