| 1. |
- Andersson, Joel, et al.
(författare)
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Semi-deterministic chemo-mechanical model of boundary lubrication
- 2012
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Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 156, s. 343-360
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Tidskriftsartikel (refereegranskat)abstract
- A model for tribofilm growth is developed. The model is used in combination with numerical contact mechanics tools to enable evaluation of the combined effects of chemistry and contact mechanics. The model is tuned with experimental data and is thereafter applied to rough surfaces. The growth of the tribofilm is evaluated for 3 different contact cases and short-term tribofilm growth behaviour is analyzed. The results show how tribofilms grow in patches. The model is expected to be used as a tool for analysis of the interaction between rough surfaces.
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| 4. |
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| 5. |
- Emadi, Maryam, et al.
(författare)
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Does your lubrication system conform to the concept of green chemistry?
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We frequently find “EAL” (environmentally acceptable lubricant or relevant such as “environmentally friendly,” “environmentally adapted,” “environmental benign,” “biodegradable,” “ecological,” “green,” in the title and keywords of tribology papers. It intimates "something good for environment" and may catch the readers' attention. However, one might feel unease because the definition of these terms is unclear. These terms are too loosely used with the authors’ satisfaction in most cases. Of course, lubrication engineering contributes to protect global environment by improving energy efficiency and prolonging machine life through reducing friction and wear. In this regard, lubrication itself is definitely one of the “green” technologies. This led a simple question – why adjectives such as “environmental” are used with lubrication? The unrivalled reference book in tribology defines “environmentally friendly lubricants” as “readily biodegradable in nature” [1]. We agree with it, but shall ask "is biodegradability enough for protection of global environment?" This motivated us to propose unambiguous criteria for EAL.
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| 6. |
- Fatima, Nowshir, et al.
(författare)
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Adsorption of ATF additives on wet clutch friction interfaces under water contaminated lubricant conditions
- 2014
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Konferensbidrag (refereegranskat)abstract
- Stable friction and positive slope of friction-speed is the typical criterion for a good clutch performance. Lubricated friction interfaces used for wet clutches produces different friction behavior depending on the lubricant conditions. Usually the lubricant conditions vary for different automatic transmission fluid (ATF) formulations implying e.g. water contamination and these conditions might influence the deterioration of the clutch plates. The aim of this paper is to verify additive adsorption on friction interfaces and ageing of the friction material in wet clutch system for a water contaminated commercial ATF (DEXRON® VI). Standard clutch plates are employed in an automated wet clutch test rig to evaluate the friction characteristics of the tested lubricant. For controlled test conditions (speed, contact pressure, oil temperature) and specific number of test cycles, the mean friction coefficient and the friction vs. speed relations are monitored during sliding test. The resultant tribofilms on the tested friction interface surfaces are characterized by means of Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM- EDS), Attenuated Total Reflectance -Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS analysis). The spectroscopic techniques were used to analyse adsorbed additives on friction interfaces and made it possible to correlate measured data to the specific friction behavior obtained after water contamination of the ATF.
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| 7. |
- Fatima, Nowshir, et al.
(författare)
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Degradation Mechanism of Automatic Transmission Fluid by Water as a Contaminant
- 2015
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Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : SAGE Publications. - 1350-6501 .- 2041-305X. ; 229:1, s. 74-85
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Tidskriftsartikel (refereegranskat)abstract
- The degradation mechanism of water contaminated Automatic Transmission Fluids (ATF) was experimentally investigated. Water contaminated ATF was tribotested in a full-scale wet clutch test rig to monitor the friction durability during clutch ageing, and was also statically aged in oven to evaluate the interaction of ATF with water. The bulk properties and chemical nature of the ATF were analysed using viscosity measurements, Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). It was shown that water presence in the ATF can increase the mean friction coefficient over a short time period, though in the long term perspective there is a higher loss of mean friction. Phase separation of the water-in-oil emulsion by centrifugation at 20000 rpm made it possible to examine the water phase using infrared 2spectroscopy. The spectroscopic analysis revealed the hydrophilic nature of certain ATF constituents, although the impact of water on the bulk properties like lubricant viscosity and thermal stability was insignificant. The analysis of the tribotests showed that the friction increase for water contamination was a short-term effect and likely due to the interaction between polar surface active additives and water. Even though no significant change has been found for thermal degradation or in bulk properties of the lubricant, the initially changed action of the water soluble additives and generation of high friction resulted in a total deterioration of the clutch performance during long term use.
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| 8. |
- Fatima, Nowshir, et al.
(författare)
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Influence of water on the tribological properties of zinc dialkyl-dithiophosphate and over-based calcium sulfonate additives in wet clutch contacts
- 2015
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 87, s. 113-120
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Tidskriftsartikel (refereegranskat)abstract
- Usually the wet clutch lubricant properties vary with different formulations of base oil types and additives. The aim of this paper was to evaluate the effect of water on the performance of additives in ATF. Simplified lubricants, ZDDP and over-based Ca-sulfonates detergent additives in an API Group I mineral base oil, were employed to compare with the commercial fully-formulated automatic transmission fluid (DEXRON®VI) during water-contamination. A full-scale wet clutch test rig was used to evaluate the frictional response due to water contamination of the lubricants. Fourier Transform Infrared Spectroscopy was utilized to evaluate the variation in the solubility of these polar organic additives in the water phase and Karl-Fischer titration was utilized to evaluate the post-test water content for different formulations.
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| 9. |
- Fatima, Nowshir, et al.
(författare)
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Surface chemistry of wet clutch influenced by water contamination in automatic transmission fluids
- 2016
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 96, s. 395-401
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Tidskriftsartikel (refereegranskat)abstract
- Lubricated friction interfaces used for wet clutches produces different friction behaviour depending on the lubricant conditions. Usually the lubricant conditions vary for water contamination in automatic transmission fluid (ATF). The presence of water retards the ATF performance by increasing the friction and can influence the deterioration of the clutch plates. Water as a polar contaminant can change the absorbability of the surface active additives, which might cause the characteristic friction behaviour. The aim of this paper is to verify the surface chemistry of tribotested standard friction interfaces lubricated with water contaminated commercial ATF (DEXRON® VI). The evidences of the influence of water on ATF performances were shown by surface analyses
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