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- Höglund, Erik, et al.
(författare)
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Experimental Investigation of the Shear Strength of Lubricants Subjected to High Pressure and Temperature
- 1986
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Ingår i: Journal of tribology. - : ASME International. - 0742-4787 .- 1528-8897. ; 108:4, s. 571-577
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Tidskriftsartikel (refereegranskat)abstract
- In order to evaluate the relationship between limiting shear strength and pressure for a lubricant an experimental apparatus has been built. Pressures up to 2. 2 GPa and temperatures up to 200 degree C are attainable simultaneously. Thus the limiting shear strength-pressure relationship has been surveyed in a wide range. Several types of natural and synthetic lubricants have been tested. The results show that all the mineral oils tested behave in quite a similar way. Synthetic lubricants do not show this behavior, but the relationship between limiting shear strength and pressure depends strongly upon the chemical base of the synthetic lubricants. The behavior of grease does not differ from that of liquid lubricants. The pressures at which the lubricants change from a liquid to a solid behavior have also been measured.
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- Höglund, Erik
(författare)
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Influence of polyalkylmethacrylate and sulphurized ester on oil film thickness in an elastohydrodynamic point contact
- 1987
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 115:1-2, s. 223-234
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this investigation is to determine how additives in a base oil affect the central oil film thickness in an elastohydrodynamic rolling point contact. The experiments have been carried out using a sapphire disc and a steel ball and the film thickness has been measured by means of optical interferometry. A detailed description of the apparatus is given.Two different additives have been used, polyalkylmethacrylate (PMA) and sulphurized ester (SE). Each of them have been mixed in a superrefined naphthenic base oil at five different concentrations.The results show that the central oil film thickness increases with increasing concentration of additive. This is because the additives increase the oil viscosity. If this effect is compensated for, 0.1 wt.% PMA or 0.63-2.5 wt.% SE give the best relative oil film build-up. There is consequently no reason to use more additive in the base oil unless one wants to have a thicker oil film because of the viscosity-increasing effect
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- Höglund, Erik
(författare)
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Relationship between lubricant shear strength and chemical composition of the base oil
- 1989
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 130:1, s. 213-224
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Tidskriftsartikel (refereegranskat)abstract
- A new method for the experimental evaluation of the shear strength of lubricants at high pressures and temperatures is presented. The main parts of the experimental apparatus are a lubricated sintered-carbide surface and an impacting steel ball. A picture-processing system is used to examine the ball trajectory after impact and to calculate the limiting shear strengthpressure coefficient of the lubricant. Using this apparatus the influence of the chemical composition of the base oil on the limiting shear strengthpressure coefficient has been investigated. It was found that the chemical structure of the oil is of major importance in determining the shear strength. Additives have no significant effect on the shear strength.
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