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- Baart, Pieter, et al.
(författare)
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Non-Newtonian effects on film formation in grease lubricated radial lip seals
- 2009
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Ingår i: Society of Tribologists and Lubrication Engineers annual meeting & exhibition 2009. - Red Hook, NY : Curran Associates, Inc.. - 9781615674374 ; , s. 140-142
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Konferensbidrag (refereegranskat)abstract
- This study investigates the high shear rheology of grease and determines whether the "normal stress effect" can significantly contribute to film formation in radial lip seal applications. Rheology measurements and a rheology model for the grease have been developed to model the normal stress at high shear rates. Subsequently, a seal lip model is developed to predict lift forces, generated by the normal stress effect. The model predicts lift forces over 50% of the seals specific lip force for low contact pressure bearing seals.
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| 3. |
- Baart, Pieter, et al.
(författare)
-
Review of the lubrication, sealing, and pumping mechanisms in oil- and grease-lubricated radial lip seals
- 2009
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Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - 1350-6501 .- 2041-305X. ; 223:3, s. 347-358
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Tidskriftsartikel (refereegranskat)abstract
- Radial lip seals are successfully used since the 1940s to seal lubricated systems. Despite extensive experimental and theoretical research in the field, it is still not fully clear how these seals function. Experimental studies, found in the public literature, show that the relatively high surface roughness of the seal lip is very important for good and reliable performance. In addition, the pressure distribution under the lip seems to be a critical factor. Six fundamental hypotheses are presented on the lubrication, pumping, and sealing mechanisms to explain the working principles of these seals. It is generally accepted that lubrication results from micro-elastohydrodynamic film build up between the rough seal surface and the shaft. Non-symmetrical tangential deformations of the lip surface are observed during experiments and assumed to act like spiral groove bearings that generate a pumping action and lubricant film. Another hypothesis suggests that the lubricant will behave non-Newtonian under the very high shear rates experienced in operating conditions. This will reduce friction because of shear-thinning and enhances sealing. Macroscopic aids, like hydrodynamic pumping aids and engineered asperity patterns on the shaft, do improve seal performance. Almost all public literature discusses oil-lubricated radial lip seals while many seals are grease lubricated, especially in certain technical fields. Due to the non-Newtonian behaviour of grease, the lubrication, sealing, and pumping mechanisms are assumed to differ from the oil-lubricated seals. Lower friction and improved protection against contamination are measured, and it is expected that the interest in grease lubrication will rapidly grow in future.
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