Estimation formula of friction coefficient of rolling-sliding contact surface under mixed lubrication condition (part 2) - Effect of surface roughness profile on friction coefficient

Susumu Matsumoto, Nobumitsu Toyota

Research output: Contribution to journalArticle


To decrease the power loss of power transmission gears, it is necessary to estimate friction coefficient at tooth meshing surface. And to prevent the failures like scuffing and pitting on tooth surface, it is necessary to decrease the flash temperature and tangential force that are proportional to friction coefficient. But there was no formula with high accuracy for estimation of friction coefficient under mixed lubrication condition considered a ratio of surface roughness and oil film thickness. In this paper, empirical validation of the new estimation formula of friction coefficient was carried out. In the contact zone under mixed lubrication, a combination of fluid friction and boundary friction exists. The new function of load ratio expressed as a simple function of the ratio of surface roughness and elastohydrodynamic lubrication minimum oil film thickness was verified. To evaluate the formula, two disc tests were conducted. The estimated values agreed well with the experimental results. The friction coefficient can be estimated by using the new function of load ratio constructed by the maximum height surface roughness. And there is no effect of average surface roughness on the friction coefficient. And there is further fact that the maximum height of grooved surface by turning can be treated as the surface with roughness height from contact surface.

Original languageEnglish
Pages (from-to)676-684
Number of pages9
JournalToraibarojisuto/Journal of Japanese Society of Tribologists
Issue number9
Publication statusPublished - 2013



  • Elastohydrodynamic lubrication
  • Friction coefficient
  • Maximum height surface roughness
  • Minimum oil film thickness
  • Mixed lubrication condition
  • Roller test
  • Rolling-sliding contact
  • Surface roughness

ASJC Scopus subject areas

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

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