1996 Fiscal Year Final Research Report Summary
STUDY ON MIXED LUBRICATION MECHANISMS OF FRACTAL SURFACES
| Project/Area Number |
07805015
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
設計工学・機械要素・トライボロジー
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
SUGIMURA Joichi Kyushu University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (20187660)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Tribology / Lubrication / Surface Roughness / Fractal / Hydrodynamic Lubrication / Mixed Lubrication / Contact. |
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| Research Abstract |
This project was aimed at establishing a theoretical ground for understanding mechanisms of film formation and contact in full hydrodynamic to mixed lubrication regimes on the basis of fractal representation of surface roughness. Mixed lubrication tests with regular microgrooves, measurements of film thickness and microcavity using a fluorensent microscope, and theoretical analyzes of hydrodynamic lubrication for fractal surfaces were conducted.
1.Mixed lubrication tests using copper specimens with regular microgrooves made by photoetching revealed that, when the angle between longitudinal direction of the grooves and the direction of motion was changed between 0 and 90 degrees, the friction coefficient and the film parameter for the onset of partial contact took on maximum at intermediate angles.
2.Point contact mixed-lubrication tests were conducted using a glass disk and steel balls having random roughness made by shot-blast. From fluorescent images and reflection images on the fluore
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scent microscope, decrease in the relative gap between the surfaces and increase in local asperity contact areas were obtained quantitatively.
3.Sliding and rolling tests were conducted with the ball/disk configuration, which showed that microcavities are generated under low macroscopic hydrodynamic pressure, and that modification of surface asperities by running-in cased increase in local hydrodynamic pressure leading to growth of microcavities.
4.A theory of hydrodynamic lubrication of fractal surfaces based on a perturbation method was established to show effects of fractal surcture on hydrodynamic lubrication. Numerical computations for an infinitely-wide inclined slider bearing were also conducted using simulated profiles created with the Fourier filtering method, and the results agreed with the theory.
5.Numerical computations of pressure for a finite width inclined bearing with simulated surfaces were conducted using a grid size of 512X512, which showed effects of fractal structures on load carrying capacity of the bearing. Less
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