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Jacobson, Staffan, Prof.ORCID iD iconorcid.org/0000-0002-3955-5746
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Publications (10 of 220) Show all publications
Larsson, E., Olander, P. & Jacobson, S. (2018). Boric acid as fuel additive: Friction experiments and reflections around its effect on fuel saving. Tribology International, 128, 302-312
Open this publication in new window or tab >>Boric acid as fuel additive: Friction experiments and reflections around its effect on fuel saving
2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 128, p. 302-312Article in journal (Refereed) Published
Abstract [en]

This paper investigates the friction reducing properties and fuel saving potential of a boric acid based fuel additive with remarkably promising results in field tests. The effect of normal load and sliding velocity on the friction behavior was studied with a reciprocating model test developed to mimic the dual lubrication from the fuel additive and the engine oil. Substantial friction reductions were achieved when repeatedly spraying the fuel additive on base oil lubricated surfaces. The friction energy loss was reduced by up to 76% compared to references without the fuel additive. We present combinations of assumptions regarding the fuel saving potential of this friction reduction that, if correct, explain the observed fuel efficiency improvements found in field tests.

Keywords
Fuel additive, Friction, Lubrication, Energy
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:uu:diva-366936 (URN)10.1016/j.triboint.2018.07.004 (DOI)000444929200030 ()
Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2018-11-28Bibliographically approved
Larsson, E., Olander, P. & Jacobson, S. (2018). Boric acid as fuel additive – Friction experiments and reflections around its effect on fuel saving. Tribology International, 128, 302-312
Open this publication in new window or tab >>Boric acid as fuel additive – Friction experiments and reflections around its effect on fuel saving
2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 128, p. 302-312Article in journal (Refereed) Published
Keywords
Fuel additive, Friction, Lubrication, Energy
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
urn:nbn:se:uu:diva-367107 (URN)10.1016/j.triboint.2018.07.004 (DOI)
Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2018-11-30
Roizard, X., Heinrichs, J., Buteri, A., Jacobson, S., Borgeot, M., Carpentiar, L., . . . Lallemand, F. (2018). Friction behavior of ferritic stainless steel in a strongly diluted alcohol solution of alkylphosphonic acid. Paper presented at 17th Nordic Symposium on Tribology (NORDTRIB), JUN 14-17, 2016, Hameenlinna, FINLAND. Tribology International, 118, 465-473
Open this publication in new window or tab >>Friction behavior of ferritic stainless steel in a strongly diluted alcohol solution of alkylphosphonic acid
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2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 118, p. 465-473Article in journal (Refereed) Published
Abstract [en]

The present study investigates the potential for using this more environmentally friendly lubrication at an industrial scale forming of stainless steel. Against this background we analyze the characteristics of the tribofilm formed on a stainless steel surface during sliding experiments performed in solutions containing alkylphosphonic acids, under various contact conditions. Specific tribological tests were designed to analyze the dynamics of the lubricating mechanism. It was found that both the grafting of molecules and the transformation of these into an efficient tribofihn are quick processes, irrespective of substrate roughness or contact pressure, systematically leading to low friction coefficient.

Keywords
Stainless steel, Forming, Low friction, Phosphonic acids
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-343657 (URN)10.1016/j.triboint.2017.04.027 (DOI)000423004700047 ()
Conference
17th Nordic Symposium on Tribology (NORDTRIB), JUN 14-17, 2016, Hameenlinna, FINLAND
Available from: 2018-05-09 Created: 2018-05-09 Last updated: 2018-05-09Bibliographically approved
Heinrichs, J., Olsson, M., Almqvist, B. & Jacobson, S. (2018). Initial surface failure and wear of cemented carbides in sliding contact with different rock types. Wear, 408-409, 43-55
Open this publication in new window or tab >>Initial surface failure and wear of cemented carbides in sliding contact with different rock types
2018 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 408-409, p. 43-55Article in journal (Refereed) Published
Abstract [en]

The initial wear, deformation and degradation of cemented carbide in contact with different rock types are studied using a crossed cylinder sliding test. The sliding distance is limited to centimetres at a time, interrupted by successive SEM analysis. This allows for careful studies of the gradually changing microstructure of the cemented carbide during the test. Five different rock types are included; granite, metal sulphide ore, mica schist, quartzite and marble. All rock types are very different in microstructure, composition and properties. The cemented carbide grade used for the evaluation contains 6 wt% Co and fine (~ 1 µm) WC grains, a grade commonly used in rock drilling. The results show that the cemented carbide microstructure becomes altered already during the very first contact with rock. The initial wear rate and wear character is highly influenced by the rock type. The initial wear of the cemented carbide is highest against quartzite and lowest against marble.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:uu:diva-351006 (URN)10.1016/j.wear.2018.04.017 (DOI)000436482000005 ()
Funder
Knowledge Foundation, 20150193
Available from: 2018-05-17 Created: 2018-05-17 Last updated: 2018-09-12Bibliographically approved
Heinrichs, J., Olsson, M., Yvell, K. & Jacobson, S. (2018). On the deformation mechanisms of cemented carbide in rock drilling: Fundamental studies involving sliding contact against a rock crystal tip. International journal of refractory metals & hard materials, 77, 141-151
Open this publication in new window or tab >>On the deformation mechanisms of cemented carbide in rock drilling: Fundamental studies involving sliding contact against a rock crystal tip
2018 (English)In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 77, p. 141-151Article in journal (Refereed) Published
Abstract [en]

Cemented carbide is a composite material, most commonly consisting of tungsten carbide grains in a metallic matrix of cobalt. The combination of a hard ceramic phase in a ductile metallic matrix combines high hardness and ability to withstand plastic deformation with toughness to avoid cracking and fracturing. Since these properties are very important in rock drilling, cemented carbides are frequently used in such applications. In earlier work, it was found that granite in sliding contact with considerably harder cemented carbides not only results in plastic deformation of the cemented carbide composite, but also in plastic deformation of some of the individual WC grains. The latter observation is remarkable, since even the two hardest granite constituents (quartz and feldspar) are significantly softer than the WC grains. This tendency to plastic deformation of the WC grains was found to increase with increasing WC grain size. The present investigation aims to increase the understanding of plastic deformation of cemented carbides in general, and the individual WC grains in particular, in a situation representative for the rock drilling application. The emphasis is put on explaining the seemingly paradoxical fact that a nominally softer counter material is able to plastically deform a harder constituent in a composite material. The experimental work is based on a scratch test set-up, where a rock crystal tip slides against a fine polished cemented carbide surface under well-controlled contact conditions. The deformation and wear mechanisms of the cemented carbide are evaluated on the sub micrometer scale; using high resolution FEG-SEM, EDS, EBSD, BIB and FIB cross-sectioning. The size of the Co-pockets, together with the shape and size of WC grains, turned out to be decisive factors in determining the degree of carbide deformation. The results are discussed with respect to their industrial importance, including rock drilling.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-363321 (URN)10.1016/j.ijrmhm.2018.04.022 (DOI)000445989200018 ()
Funder
Knowledge Foundation
Available from: 2018-10-16 Created: 2018-10-16 Last updated: 2018-11-28Bibliographically approved
Westlund, V., Heinrichs, J. & Jacobson, S. (2018). On the Role of Material Transfer in Friction Between Metals: Initial Phenomena and Effects of Roughness and Boundary Lubrication in Sliding Between Aluminium and Tool Steels. Tribology letters, 66(3), Article ID 97.
Open this publication in new window or tab >>On the Role of Material Transfer in Friction Between Metals: Initial Phenomena and Effects of Roughness and Boundary Lubrication in Sliding Between Aluminium and Tool Steels
2018 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 3, article id 97Article in journal (Refereed) Published
Abstract [en]

In the absence of a lubricant, the friction we measure in sliding contact between metals is typically high and quite erratic, with rapid fluctuations. If we filter out these rapid fluctuations, we can typically also notice slower trends, which can lead to quite dramatic friction changes. Unless careful studies are performed, the cause to this behaviour cannot be understood. How come a material couple cannot be characterised with a specific coefficient of friction? The present paper sets out to add understanding to this area, by conduction and analysing an experimental series involving sliding between a needle-like aluminium tip against tool steel flats. The load is high enough to cause substantial plastic deformation of the aluminium needle; its tip becomes formed by the contact against the tool steel. These small-scale, low sliding distance tests facilitate detailed studies of the initial stages of various friction trends, and the effects of initial surface roughness and shifts of this roughness caused by material transfer between the sliding surfaces. Specifically, the effects on the transfer and friction behaviour from presence or absence of a boundary lubricant film and atmospheric oxygen were studied. It was found that very smooth sliding surfaces can offer low-friction conditions for these metal types. However, the smooth sliding interface is very fragile. In all unlubricated cases tested, it very rapidly (in less than a few mm sliding) became ruined due to transfer, and the friction level correspondingly increased. The boundary lubricant could only offer low friction in cases where the flat steel surface was very smooth. The lubricant also facilitated smoothening of transferred aluminium. As long has been well known, boundary lubrication films typically do not totally hinder direct metallic contact in solid to solid contact. The present results strengthen this view and further suggests that in these direct contacts one of the major friction reducing effects of the lubricant is to efficiently limit transfer, which otherwise acts to make the sliding surface rough.

Place, publisher, year, edition, pages
SPRINGER/PLENUM PUBLISHERS, 2018
Keywords
Friction, Roughness, Material transfer, Lubrication, Friction fundamentals
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:uu:diva-360176 (URN)10.1007/s11249-018-1048-4 (DOI)000437046400001 ()
Funder
Swedish Research Council, 621-2013-5858
Available from: 2018-09-12 Created: 2018-09-12 Last updated: 2018-09-12Bibliographically approved
Elo, R., Heinrichs, J. & Jacobson, S. (2018). Surface texturing to promote formation of protective tribofilms on combustion engine valves. Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, 232(1), 54-61
Open this publication in new window or tab >>Surface texturing to promote formation of protective tribofilms on combustion engine valves
2018 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 232, no 1, p. 54-61Article in journal (Refereed) Published
Abstract [en]

In a combustion engine, the valve system controls the flow of gases in to and out of the combustion chamber.The contacting surfaces experience a harsh tribological situation with high temperatures, high speed impacts, corrosiveenvironment and high closing forces causing micro sliding in the interface. The components have to endure in the rangeof hundreds of millions to a billion operational cycles, resulting in extreme demands on low wear rate. Such low wearrates can be accomplished by the protective action from tribofilms forming from oil residues, avoiding a pure metal-tometalcontact. Such tribofilms are found on well-functioning engine valves from a variety of engines, but some stationarygas engines experience problems with wear occurring seemingly randomly at normal running conditions. For somereason, the tribofilm has not protected the surfaces sufficiently, causing wear. One way to combat the random behaviourcould be to promote robust function of the protective tribofilms by texturing the valve sealing surfaces to improve thecapture and storage of oil residues. By stabilising the supply in this way, the damage from periods with low access totribofilm forming material could be reduced. The present work demonstrates that turning of the valve seat inserts,creating valleys perpendicular to the sliding motion, can be developed into a useful solution. The amount and localisationof tribofilms became more predictable and stable than without the texture, leading to reduced component wear. Thevalleys should not be too wide, since this increased the amount of exposed metal if the tribofilm flaked off. When havingthe same width, the deeper valleys showed less flaking off of the tribofilm.

Keywords
Tribofilm formation, combustion engine valve, surface texture, rig testing, scanning electron microscopy
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-335323 (URN)10.1177/1350650117739738 (DOI)000419852700006 ()
Available from: 2017-12-04 Created: 2017-12-04 Last updated: 2018-02-22Bibliographically approved
Larsson, E., Olander, P. & Jacobson, S. (2018). Tribofilm formation of a boric acid fuel additive – Investigation of tribofilm properties. In: : . Paper presented at Nordtrib 2018, June 18-21, 2018, Uppsala, Sweden.
Open this publication in new window or tab >>Tribofilm formation of a boric acid fuel additive – Investigation of tribofilm properties
2018 (English)Conference paper, Oral presentation with published abstract (Other academic)
Keywords
Boric acid, Fuel additive, Lubrication, Tribofilm
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
urn:nbn:se:uu:diva-367109 (URN)
Conference
Nordtrib 2018, June 18-21, 2018, Uppsala, Sweden
Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2018-11-30
Heinrichs, J., Kawakami, A., Mikado, H., Wiklund, U., Kawamura, S. & Jacobson, S. (2018). Wear mechanisms of WC-Co cemented carbide tools and PVD coated tools used for shearing Cu-alloy wire. In: : . Paper presented at Nordtrib, June 18-21, Uppsala, Sweden.
Open this publication in new window or tab >>Wear mechanisms of WC-Co cemented carbide tools and PVD coated tools used for shearing Cu-alloy wire
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2018 (English)Conference paper, Oral presentation with published abstract (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-367110 (URN)
Conference
Nordtrib, June 18-21, Uppsala, Sweden
Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2018-11-30
Larsson, E., Olander, P. & Jacobson, S. (2017). Boric acid as a lubricating fuel additive - Simplified lab experiments to understand fuel consumption reduction in field test. Paper presented at 21st International Conference on Wear of Materials (WOM), MAR 26-30, 2017, Long Beach, CA, USA. Wear, 376, 822-830
Open this publication in new window or tab >>Boric acid as a lubricating fuel additive - Simplified lab experiments to understand fuel consumption reduction in field test
2017 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 376, p. 822-830Article in journal (Refereed) Published
Abstract [en]

In field tests, a boric acid based fuel additive has led to reduced fuel consumption. The reduction was substantial, an average of 6 and 10% in passenger cars and diesel generators respectively. Aiming towards improved understanding of mechanisms behind the fuel saving, three methods to mimic the effect of the additive in the piston-ring/cylinder contact have been evaluated. A reciprocating cylinder/flat configuration with ball bearing steel against grey cast iron was used, and it was lubricated with base oil. The different methods were as following: A) repeated spraying of a small amount of the boric acid solution onto the surfaces, B) predeposition of a boric acid layer on the flat surface and C) a combination of method A) and B). The three methods all showed effects of the additive, spanning from about 20% to 50% reductions (in the latter case, from roughly 0.1 to 0.05 in coefficient of friction averaged over the stroke). The greatest potential of the additive was seen with local coefficient of frictions lower than 0.020 in tests at room temperature with Method C. This means a reduction of around 75% compared to the lowest levels measured for the reference tests run without the additive. The most stable friction test was Method A, where a small amount of boric acid solution was repeatedly sprayed onto the lubricated sliding surfaces. In this type of test, friction reductions of roughly 20% and 40% were found at 100 C and room temperature respectively. The tribological and chemical mechanisms of boric acid in this test configuration are yet not fully understood and more studies are needed. However, the observed poor stability of the tribofilms containing boron and oxygen complicates such activities.

Keywords
Boric acid, Lubrication, Friction, Fuel consumption, Fuel additive
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-329131 (URN)10.1016/j.wear.2017.01.105 (DOI)000403904000093 ()
Conference
21st International Conference on Wear of Materials (WOM), MAR 26-30, 2017, Long Beach, CA, USA
Funder
VINNOVA
Available from: 2017-10-10 Created: 2017-10-10 Last updated: 2017-11-29Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3955-5746

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