| 1. |
- Isaksson, Ove
(författare)
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Measurement of the influence of sliding velocity on oil film thickness in an elastohydrodynamic point contact
- 1991
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 4:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Experiments have been carried out to measure the film thickness between a sapphire disc and a polished steel ball when slippage is permitted between the two surfaces. The velocity sum of the two surfaces was kept constant during the measurements. The method used to determine the oil film thickness in the contact zone is optical interferometry. It was observed that the change in minimum film thickness was slight. When the sliding velocity was increased, the decrease in central film thickness was considerably larger than that of the minimum film thickness. In addition, the two side lobes, in which the minimum film thickness area occurs, were observed to become flatter as the sliding velocity was increased
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| 2. |
- Isaksson, Ove, et al.
(författare)
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Pressure-viscosity coefficient of a refrigerant-oil mixture : [Coefficient pression-viscositéd'un mélange frigorigène-huile]
- 1993
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Ingår i: International journal of refrigeration. - 0140-7007 .- 1879-2081. ; 16:2, s. 139-142
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Tidskriftsartikel (refereegranskat)abstract
- A coaxial cylinder viscosimeter has been used to determine the pressure-viscosity coefficient of a pure refrigeration oil and of a mixture of refrigerant and oil at gauge pressures up to 15 MPa. The test fluid, Gargoyle Arctic oil 300, is a naphthenic-base oil. The refrigerant was R22, chlorodifluoromethane, which is a commercially important refrigerant. In a gap apparatus the refrigerant-oil mixture has been visually inspected at different pressures. Two different mechanisms are involved in the refrigerant-oil mixture: the change in solubility with pressure and the change in viscosity with refrigerant concentration. If the mixture is pressurized with excess refrigerant available then the concentration of refrigerant will increase with increasing pressure and therefore the viscosity will decrease. If the concentration is kept at a constant level then the viscosity will increase with pressure. The results from the cylinder viscosimeter showed that the viscosity increase with pressure for the mixture was almost the same as for the pure oil
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| 3. |
- Åström, Henrik, et al.
(författare)
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Video recordings of an EHD point contact lubricated with grease
- 1991
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Ingår i: Tribology International. - 0301-679X .- 1879-2464. ; 24:3, s. 179-184
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Tidskriftsartikel (refereegranskat)abstract
- Optical interferometry has been used to study the film thickness of an EHD point contact lubricated with grease. The greases used were two lithium, two lithium complex and two sodium greases, all with NLGI grade two, the most common grade. They were based on one mineral oil of naphthenic type and one synthetic polyalphaolefin. The contact was lubricated without a continuous supply of grease and thus the film thickness decreased with time as the grease was gradually squeezed away from the contact area. The film thickness fluctuated during the measurement. To overcome this problem, the contact point was recorded with a video camera and the results evaluated after the tests. The video camera proved to be a powerful help in this evaluation. The tests were run at 20°C and under pure rolling conditions at a rolling velocity of 0.055 m s-1. The results from all greases showed a decreasing film thickness that tended to stabilize on about 0.2 μm after 40 cycles. The lithium and lithium complex greases showed strong local film thickness variations inside the lubricated contact, deviating from the normally horseshoe-shaped contact, during the first 20 to 40 cycles.
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| 4. |
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| 5. |
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| 6. |
- Gustafsson, Lennart, et al.
(författare)
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Measuring lubricant film thickness with image analysis
- 1994
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Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - 1350-6501 .- 2041-305X. ; 208:3, s. 199-205
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Tidskriftsartikel (refereegranskat)abstract
- Determining lubricant film thickness between contacting bodies under elastohydrodynamic (EHD) conditions is often simulated by using a ball/cylinder and transparent disc apparatus together with an interferometry technique. The simulated contact will have a point or elliptic shape and the light used can be white or monochromatic. The interference pattern is normally photographed with a regular camera or a video camera and the pictures are then evaluated by the naked eye of the observer. In most cases, only central or minimum thicknesses are evaluated.In this paper an image processing method for the analysis of film thickness is presented. This method makes it possible to extract considerably more information about film thickness fluctuations than is achievable by the naked eye. The method primarily matches hue (but also saturation and intensity values) from digitized colour interferometric images of the unknown film shapes with calibration values obtained with known geometric shapes.The method is shown to work well in the range from 95 up to 700 nm with white light and makes the results unbiased by the observer. Furthermore, absolute film thickness can be evaluated without prior knowledge about the fringe order in the interferogram.
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| 7. |
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| 8. |
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| 9. |
- Kassfeldt, Elisabet, et al.
(författare)
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Lubricant capability in squeeze-sliding motion
- 1993
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Ingår i: Thin films in tribology. - Amsterdam : Elsevier. - 0444897895 ; , s. 255-261
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Konferensbidrag (refereegranskat)abstract
- Nine different types of commercial lubricants have been tested in an apparatus which can produce squeeze and sliding motion simultaneously. It is found that lubricants with the same viscosity show big differences in lubricant capability in terms of wear and oil film collapse, and that these differences are due to the additives
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| 10. |
- Larsson, Roland, et al.
(författare)
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Simplified solution to the combined squeeze-sliding lubrication problem
- 1994
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 173:1-2, s. 85-94
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Tidskriftsartikel (refereegranskat)abstract
- The unfavourable elastohydrodynamic lubrication situation in combined squeeze and sliding motion has been analysed both theoretically and experimentally. In experiments a rotating roller impacted and rebounded on a lubricated surface. It was found that oil film breakdown always occurs at the end of the impact time, when the contact force is low. It has also been found that there exists an upper limit for the sliding velocity. Below this limiting velocity no oil film breakdown occurs. This paper is an initial attempt to explain theoretically why oil film breakdown takes place towards the end of the impact, and why an increasing sliding velocity reduces the capability of the oil film to separate the lubricated surfaces. If the oil film's elastic and damping behaviour are taken into consideration it can be shown that a considerable phase shift between maximum contact force and oil film breakdown will arise. It has been found that the squeeze action dominates the pressure formation in the contact and thus the hydrodynamic effect of sliding motion is moderate. Furthermore, several effects, such as non-Newtonian behaviour, surface roughness, temperature rise, starvation and deformations, which are not included in the theoretical model, may decrease the oil film thickness if the sliding velocity increases
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