| 1. |
- Almqvist, Andreas, et al.
(författare)
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Selected papers from those presented at the 3rd International Tribology Symposium of IFToMM
- 2014
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 26:5, s. 273-275
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Selected papers presented at the 3rd International Tribology Symposium of the International Federation for the Promotion of Mechanism and Machine Science (IFToMM) are discussed. The 3rd International Tribology Symposium of IFToMM was organized by the Division of Machine Elements of Luleå University of Technology in Sweden from March 19 21, 2013. The symposium was held in the university campus, providing a perfect forum for the tribologists for presenting their latest research and exchange of ideas. The participants were also given the opportunity to experience the snowy landscape during a memorable outdoor dinner. The symposium attracted 146 participants from 26 countries along with 92 papers spread over 32 sessions. These papers covered the fundamental and applied aspects of wide ranging topics such as friction, wear, lubrication, lubricants, tribology in hostile environment, tribomaterials, solid lubricants, surface engineering, and tribotesting.
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| 2. |
- Berglund, Kim, et al.
(författare)
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Evaluating lifetime performance of limited slip differentials
- 2014
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 26:3, s. 189-201
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Tidskriftsartikel (refereegranskat)abstract
- Extensive research has been performed regarding wet clutch function and performance. Although wet clutches are used in both automatic transmissions and limited slip differentials in cars, most research has been performed for wet clutches incorporated in automatic transmissions. The operating conditions of wet clutches in automatic transmissions differ from the operating conditions of the wet clutches used in limited slip differentials. Therefore, a method and a test bench to use in the investigation of the degradation of limited slip differentials were developed in this work. The typical operating conditions of the limited slip differential and the differences compared with wet clutches incorporated in automatic transmissions were also addressed. Tests performed showed that the developed test bench and method can be used to address differences in frictional response over time for different types of operating condition
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| 3. |
- Dhakal, Nayan, et al.
(författare)
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Tribological behaviour of UHMWPE composites lubricated by polyvinylpyrrolidone‐modified water
- 2022
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Ingår i: Lubrication Science. - : John Wiley & Sons. - 0954-0075 .- 1557-6833. ; 34:1, s. 42-53
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Tidskriftsartikel (refereegranskat)abstract
- Tribological characteristics of ultra-high molecular weight polyethylene (UHMWPE) composites with 10% short carbon fibres (SCF) lubricated in water with polyvinylpyrrolidone (PVP) as a modifier were investigated. The aqueous solutions with varying concentrations of PVP were prepared, and their viscosity-enhancing action, friction-reducing properties and anti-wear performances were studied under different loading conditions equivalent to 10 and 20 MPa of contact pressures at a constant sliding speed of 20 mm/s. The results showed that PVP is an excellent viscosity modifier for water. PVP-modified water exhibited excellent performance compared to distilled water, reducing the wear and friction coefficient of neat UHMWPE up to 25%. The anti-wear properties of UHMWPE-SCF composite were also improved with PVP modified water lubrication, yielding a maximum reduction of wear up to 45%. PVP seems to be a promising additive of modifying the lubricating properties of distilled water for water-based lubrication.
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| 4. |
- Eriksson, Erland, et al.
(författare)
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Electrical resistivity and conductivity of greases : an initial study
- 2002
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 15:1, s. 33-50
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Tidskriftsartikel (refereegranskat)abstract
- Investigations of railway wagons fitted with rolling-element bearings have shown damage to the bearings from the passage of electric current. This also occurs in railway wagons without an electric energy consumption of their own, because of residual currents from electric locomotives. This phenomenon gives rise to technical, financial, and even safety problems. This paper reviews research in the field of rolling-element bearings exposed to electric currents. The paper also reports on an ongoing study undertaken to understand the mechanism of current flow and the role of lubricants in the associated damage, and to identify the possibilities of minimising bearing damage. The obvious solution to this problem is to use optimised greases, i.e., with high electrical conductivity and good lubricating ability. In the preliminary work reported here a number of greases for railway use were tested to determine their electrical conductivity in static and dynamic situations. These tests were performed using specially designed apparatus, and significant initial information about the electrical properties of greases has been obtained in this research, for example, that there is a correlation between the electrical conductance under static and dynamic conditions. All the greases tested showed comparatively high resistivity values, which could be one explanation for the bearing damage observed.
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| 5. |
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| 6. |
- Glavatskikh, Sergei B., et al.
(författare)
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Oil film thickness measurement by means of an optic lever technique
- 2000
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 13:1, s. 23-35
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Tidskriftsartikel (refereegranskat)abstract
- Oil film thickness in hydrodynamic bearings is a fundamental parameter influencing overall hydrodynamic bearing performance. Knowledge of this thickness allows bearing performance to be optimized. For the small hydrodynamic bearings that are usually used in laboratory test facilities, a very small sensor (e.g., <2 mm) is required because of space limitations. Commercially available eddy-current and capacitance sensors are too large to be mounted in the pad of such a bearing. An alternative approach is to use sensors based on optical methods, such as the optic lever technique. The main idea in this technique is to detect the intensity of a light beam reflected from a target surface. This intensity is a function of the distance between the sensor and the target. This paper reports the specific features of the optic lever technique as used for measurements of oil film thickness. The design, calibration procedure, and main characteristics of an optical sensor are discussed. A test rig for the calibration of oil film thickness sensors is also presented. The sensor response curve has two parts, linear and non-linear; using the linear part results in high sensitivity in the micrometre range. The influence of different types of oil on the output signal of the sensor has also been investigated. Experiments with different target velocities have shown that this sensor can be used for accurate and reliable measurement of oil film thickness in hydrodynamic bearings
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| 7. |
- Gondal, A. K., et al.
(författare)
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Studies on tribological behaviour of two oil soluble molybdenum compounds under reciprocating sliding conditions
- 1993
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 5:4, s. 337-359
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Tidskriftsartikel (refereegranskat)abstract
- The use of oil-soluble organo-molybdenum compounds in engine oils can help in fuel conservation by reducing engine friction and increase durability by improving wear characteristics. The tribological behaviour of molybdenum dialkyldithiophosphate (MoDDP) was studied with a SRV Optimol tester under reciprocating sliding conditions. The studies were conducted under nonconformal contact conditions on En-31 steel and conformal contact conditions on piston ring and liner materials. The results indicated that the frictional behaviour of these additives is shear sensitive. Shear sensitivity is influenced by materials, operating conditions and the interaction of MoDDP with additives present in the oil. MoDDP when used in base oil was found to increase the scuff resistance of ring and liner materials. The use of the additive reduced friction and wear (running in as well as normal) under nonconformal contact conditions, while under conformal contact conditions its effect was selective and limited.
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| 8. |
- Gren, Per, et al.
(författare)
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Feasibility of using digital speckle correlation in the study of seal contacts
- 2009
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 21:4, s. 123-134
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents studies of the contact between a soft rubber specimen and glass counterface using the Digital Speckle Correlation method, which provides information of displacements and structural similarities between recorded images. The setup is designed with a real contact and changes in the contact can be varied. Microscopic images using laser light illumination for different displacements are recorded and correlated. The results show that the contact area can be identified both for dry and lubricated contacts. The method can be applied on different geometries, surface roughness and lubricants. Influences of scars and contaminations, e.g. wear particles, may also be analysed.
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| 9. |
- Hatami, Sepehr, 1981, et al.
(författare)
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Tribological properties of powder metallurgical tool steels used in powder compaction pressing dies
- 2011
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Ingår i: Lubrication Science. - : Wiley. - 0954-0075 .- 1557-6833. ; 23:3, s. 139-152
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Tidskriftsartikel (refereegranskat)abstract
- The tribological properties of two powder metallurgical (PM) tool steels, high and low nitrogen containing, are investigated by means of three different wear tests: ball-on-disc, rubber wheel and scratch test. The ball-on-disc tests showed two distinct friction curves corresponding to each material. In order to simulate the tribosystem existing in metal powder compaction dies, the rubber wheel and the scratch test were modified. The rubber wheel test was performed using ferrous powder instead of sand, and scratch testing was carried out by sliding a powder compact over the tool steels. The scratch tests indicated a higher steady-state coefficient of friction for the low nitrogen containing PM steel as compared with the high nitrogen containing alloy. Additionally, the results from the rubber wheel tests were in agreement with industrial experiences, showing the low nitrogen containing tool steel to suffer from severe galling. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 10. |
- 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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