Study of Fluid Film Formation and Friction Characteristics of Radial Lip Seals

Yuki Sato, Joichi Sugimura, Yuji Yamamoto

Research output: Contribution to journalArticlepeer-review


Oil seals that show sealing efficiency with the presence of a sufficient surface roughness on the sliding surface and oil seals that show leakage due to very low surface roughness were studied by measuring the oil film thickness on the sliding surface in sealing, pumping, and leakage states. At a low dimensionless characteristic number G, the coefficient of friction of seal, which have low roughness and do not develop pumping action was lower than the coefficient of friction of seals which have larger surface roughness and develop sealing action. The sealing ability of seals increased with an increase of the parameter G. At the maximal parameter G, the coefficient of friction of seals with sealing ability was two times higher. The average oil film thickness in the state of sealing on seals with a rough surface and sealing ability grew gradually smaller from the oil vessel side toward the air side, the thickness being ∼ 1-10 μm. At the state of pumping, the oil film thickness was larger than at the state of sealing. At the state of sealing, many microscopic cavities develop on the sliding surface and the surface area that was covered by cavities increased with the speed of shaft rotation. On the other hand, the oil film thickness of material (FKM-B) with low roughness, smooth surface, and no sealing ability was ∼ 1 μm and oil film had a smooth profile in a wide range of the sliding surface. A change of the speed of rotation caused practically no change. The development of microscopic cavities was not observed.

Original languageEnglish
Pages (from-to)307-320
Number of pages14
JournalJapanese Journal of Tribology
Issue number3
Publication statusPublished - 2003
Externally publishedYes

All Science Journal Classification (ASJC) codes

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


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