1990 Fiscal Year Final Research Report Summary
Effects of Surface Roughness and Visco-Elastic or Elastic-Plastic Characteristics in Ehl
| Project/Area Number |
63460086
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
機械要素
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| Research Institution | Kyushu Institute of Technology |
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Principal Investigator |
KANETA Motohiro Kyushu Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (90039123)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUDA Kennji Kyushu Institute of Technology, Faculty of Engneering, Lecturer, 工学部, 講師 (40229480)
NISHIKAWA Hiroshi Kyushu Institute of Technology, Faculty of Engineering, Research Associate, 工学部, 助手 (40208161)
SUZUKI Hiroshi Kyushu Institute of Technology Faculty of Computer Science and Systems Engineeri, 情報工学部, 助教授 (00144204)
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| Project Period (FY) |
1988 – 1990
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| Keywords | Tribology / Rolling contact / EHL theory / Surface roughness / Non-Newtonian fluid / Wall slip / Micro-EHL / Modulus of Elasticity |
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| Research Abstract |
Using optical interferometry technique film profiles in circular elastohydrodynamic contacts are examined with several kinds of fluid under wide ranges of loads and speeds. As a result, it was suggested that in order to have a clearer understanding of the cause of surface failure and methods for its prevention, the elastohydrodynamic lubrication (EHL) theory should be reconstructed by considering the solidification phenomenon of lubricating oils, effects of the difference in elastic moduli of the contacting surfaces, pressure components parallel to the contacting surfaces and surface roughness. The main results obtained are summarized as follows :
(1) In pure rolling, the oil film in EHL exhibits solid-like behavior. However, in sliding the flow characteristics of EHL film depend on the molecular structure of lubricating fluids. That is, a solidified or closely packed oil collapses under external shearing force, and the film shape exhibits a tapered wedge so that the minimum film thickn
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ess becomes thinner than the theoretical prediction. Some oils, however, slip at or near the interface between the fluid and the surfaces, and consequently they keep their closely packed state during the pass through the contact region.
(2) If the contacting bodies are different in their elastic moduli, the EHL film shape is markedly influenced by the slide/roll ratio even if the rolling or entrainment velocity is kept constant. In particular, if the surface having a low elastic modulus is faster than that having a high elastic modulus, a local thickening of the film (dimple) occurs in the contact surface in place of the flat plateau predicted by the EHL theory.
(3) Asperities behave differently in rolling and sliding. In pure rolling, the film behavior is almost the same as that obtained using the smooth surfaces, although the asperity has a microconstriction on the leading edge by the squeeze action. However, in sliding, the film shape is markedly affected by the position and the lay of asperity. In particular, when there exists the wall slip, the film profile changes with time. Less
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