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Publications (10 of 234) Show all publications
Björling, M., Habchi, W., Bair, S., Larsson, R. & Marklund, P. (2019). Erratum: Towards the true prediction of EHL friction (ed.). Tribology International, 133, 297-297
Open this publication in new window or tab >>Erratum: Towards the true prediction of EHL friction
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2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 133, p. 297-297Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73121 (URN)10.1016/j.triboint.2018.10.018 (DOI)
Note

Erratum in: Tribology International, vol. 66, p.19-26, DOI:10.1016/j.triboint.2013.04.008

Available from: 2019-03-06 Created: 2019-03-06 Last updated: 2019-03-06Bibliographically approved
Hultqvist, T., Vrček, A., Prakash, B., Marklund, P. & Larsson, R. (2019). Influence of lubricant pressure response on sub-surface stress in elastohydrodynamically lubricated finite line contacts. Journal of tribology, 141(3), Article ID 031502.
Open this publication in new window or tab >>Influence of lubricant pressure response on sub-surface stress in elastohydrodynamically lubricated finite line contacts
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2019 (English)In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 141, no 3, article id 031502Article in journal (Refereed) Published
Abstract [en]

In order to adapt to increasingly stringent CO2 regulations, the automotive industry must develop and evaluate low cost, low emission solutions in the powertrain technology. This often implies increased power density and the use of low viscosity oils, leading to additional challenges related to the durability of various machine elements. Therefore, an increased understanding of lubricated contacts becomes important where oil viscosity-pressure and compressibility-pressure behaviour have been shown to influence the film thickness and pressure distribution in EHL contacts, further influencing the durability. In this work, a finite line EHL contact is analysed with focus on the oil compressibility- and viscositypressure response, comparing two oils with relatively different behaviour and its influence on subsurface stress concentrations in the contacting bodies. Results indicate that increased pressure gradients and pressure spikes, and therefore increased localized stress concentrations, can be expected for stiffer, less compressible oils, which under transient loading conditions not only affect the outlet but also the edges of the roller

Place, publisher, year, edition, pages
ASME Press, 2019
Keywords
Elastohydrodynamic lubrication; Finite line contacts; Sub-surface stress; Transient loading
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-71551 (URN)10.1115/1.4041733 (DOI)000457029800007 ()2-s2.0-85057759100 (Scopus ID)
Funder
Swedish Energy Agency, 41215-1
Note

Validerad;2018;Nivå 2;2018-12-07 (johcin)

Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2019-02-21Bibliographically approved
Hansen, J., Björling, M. & Larsson, R. (2019). Mapping of the lubrication regimes in rough surface EHL contacts. Tribology International, 131, 637-651
Open this publication in new window or tab >>Mapping of the lubrication regimes in rough surface EHL contacts
2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 131, p. 637-651Article in journal (Refereed) Published
Abstract [en]

Understanding film formation in rough surface elastohydrodynamically lubricated (EHL) contacts have been an ongoing pursuit in lubrication science for more than half a century. This study furthers that quest by establishing a single combined friction and electrical contact resistance map that forms a clear and comprehensive overview of the lubrication performance. A ball-on-disc machine was operated under a wide variety of heavily loaded rolling/sliding contact conditions. Results show that while sweeping the contact over the SRR- and entrainment speed-domain, the primary sweep direction significantly affects running-in and consequently the transition from full-film to the mixed lubrication regime. Such knowledge sheds new light into the mechanisms that governs EHL film formation and the concurrent interplay with the mixed lubricated friction coefficient.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Rough surface EHL, Friction, Stribeck curve, Running-in
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-71681 (URN)10.1016/j.triboint.2018.11.015 (DOI)000456766000062 ()2-s2.0-85057507855 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-12-05 (johcin)

Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2019-02-21Bibliographically approved
Vrček, A., Hultqvist, T., Baubet, Y., Björling, M., Marklund, P. & Larsson, R. (2019). Micro-pitting and wear assessment of engine oils operating under boundary lubrication conditions. Tribology International, 129, 338-346
Open this publication in new window or tab >>Micro-pitting and wear assessment of engine oils operating under boundary lubrication conditions
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2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 129, p. 338-346Article in journal (Refereed) Published
Abstract [en]

Current state-of-the-art engine oils tend to enhance micro-pitting damage in rolling contacts under certain operating conditions. ZDDP anti-wear additive was shown to promote such behavior. However, in order to optimize an engine oil formulation for rolling contacts, further studies are needed to assess engine oils in terms of micro-pitting and wear damage. This investigation studies the micro-pitting and wear performance of a number of engine oils for rolling contacts in a ball-on-disc configuration under conditions prevalent in crankshaft roller bearing applications. Based on the results it was concluded that an engine oil containing higher blend of PAO base oil compared to the oil mixture of Group III and PAO has a lower tendency towards micro-pitting and wear.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-70731 (URN)10.1016/j.triboint.2018.08.032 (DOI)000447575600028 ()2-s2.0-85052642062 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-09-24 (inah)

Available from: 2018-09-03 Created: 2018-09-03 Last updated: 2018-11-01Bibliographically approved
Vrček, A., Hultqvist, T., Baubet, Y., Björling, M., Marklund, P. & Larsson, R. (2019). Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction. Lubricants, 7(5), Article ID 42.
Open this publication in new window or tab >>Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction
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2019 (English)In: Lubricants, E-ISSN 2075-4442, Vol. 7, no 5, article id 42Article in journal (Refereed) Published
Abstract [en]

Under certain operating conditions, rolling contacts have been shown to experience some challenges when lubricated with engine oils containing zinc dialkyldithophosphate (ZDDP) anti-wear additive. In order to better understand the main damage mechanisms during various operating conditions, further studies are needed. This article studies micro-pitting and wear damages of bearing steel surfaces under mixed lubrication conditions in a ball-on-disc setup, lubricated with different engine oils. Based on the results, micro-pitting and wear damage is shown to be highly case-dependent. In general, PAO-based engine oil tends to eliminate micro-pitting damage compared to mineral-based engine oil at less severe lubricating conditions. Moreover, a critical lambda was found for both oils, where the highest micro-pitting damage was observed. 

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
micro-pitting, ZDDP, mild wear, surface-initiated fatigue
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-75059 (URN)10.3390/lubricants7050042 (DOI)000470959700003 ()2-s2.0-85066431252 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-27 (johcin)

Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-06-27Bibliographically approved
Vrček, A., Hultqvist, T., Baubet, Y., Marklund, P. & Larsson, R. (2019). Micro-pitting Damage of Bearing Steel Surfaces under Mixed Lubrication Conditions: Effects of Roughness, Hardness and ZDDP Additive. Tribology International, 138, 239-249
Open this publication in new window or tab >>Micro-pitting Damage of Bearing Steel Surfaces under Mixed Lubrication Conditions: Effects of Roughness, Hardness and ZDDP Additive
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2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 138, p. 239-249Article in journal (Refereed) Published
Abstract [en]

Micro-pitting presents a failure of the rolling/sliding contact metal asperities operating under boundary/mixed lubrication conditions. The studies have shown that micro-pitting failure competes with mild wear and that lubricant additives can have either detrimental or beneficial effects on micro-pitting evolution. This article describes a methodology to investigate micro-pitting damage on bearing steels using a twin-disc machine to better represent mechanical components, i.e. bearings, crankshafts, etc. In addition, effects of roughness, hardness and the ZDDP additive are presented and discussed. A sufficient hardness difference can completely eliminate micro-pitting damage mode. Furthermore, the presence of ZDDP anti-wear additive in fully formulated engine oil was shown to protect rougher surfaces and promote wear on smoother surfaces, thus completely eliminating the micro-pitting damage mode.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Micro-pitting, Mild wear, Hardness, ZDDP
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-75061 (URN)10.1016/j.triboint.2019.05.038 (DOI)2-s2.0-85066476632 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-27 (johcin)

Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-06-27Bibliographically approved
Wu, J., Mu, L., Feng, X., Lu, X., Larsson, R. & Shi, Y. (2019). Poly(alkylimidazolium bis(trifluoromethylsulfonyl) imide)-Based Polymerized Ionic Liquids: A Potential  High-Performance Lubricating Grease. Advanced Materials Interfaces, 6(5), Article ID 1801796.
Open this publication in new window or tab >>Poly(alkylimidazolium bis(trifluoromethylsulfonyl) imide)-Based Polymerized Ionic Liquids: A Potential  High-Performance Lubricating Grease
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2019 (English)In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 6, no 5, article id 1801796Article in journal (Refereed) Published
Abstract [en]

Polymers prepared from ionic liquids are widely called polymerized ionic liquids (PILs). Compared to monocationic and dicationic ILs, PILs have higher molecular weights, charge, and greater intermolecular interactions, which make PILs have a higher possibility to generate better lubricity. PILs of poly‐alkylimidazolium bis(trifluoromethylsulfonyl)imide (PImC6NTf2) is studied herein. Dicationic ILs of 1,1′‐(pentane‐1,5‐diyl)‐bis(3‐butylimidazolium) bis(trifluoromethylsulfonyl)imide (BIm5‐(NTf2)2) is used as additive to decrease the crystallization temperature of PImC6NTf2. Lubricity of PImC6NTf2 and PImC6NTf2+BIm5‐(NTf2)2, as well as BIm5‐(NTf2)2 for comparison is evaluated under severe conditions, i.e., 3.0 to 3.5 GPa and 200 °C. The rheological study suggests that PImC6NTf2 can be classified into grease. Tribological test results show that PImC6NTf2 has much better antiwear property than BIm5‐(NTf2)2, especially at 3.5 GPa. Adding 4% BIm5‐(NTf2)2 to PImC6NTf2 is able to reduce friction under high pressure. At 200 °C, PImC6NTf2 exhibits excellent lubricity. The mixture of 96%PImC6NTf2+4%BIm5‐(NTf2)2 shows even better antiwear property than neat PImC6NTf2 and exhibits the highest friction reducing property among the ILs at 200 °C. It is speculated that the robust strength of PILs and strong adhesion between PILs and solids are key factors in achieving the excellent antiwear property.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
grease, high pressure and high temperature, lubricity, polymerized ionic liquids
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-72623 (URN)10.1002/admi.201801796 (DOI)000460657100002 ()
Note

Validerad;2019;Nivå 2;2019-03-11 (johcin)

Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-06-14Bibliographically approved
Björling, M., Habchi, W., Bair, S., Larsson, R. & Marklund, P. (2018). Correction to: Friction reduction in elastohydrodynamic contacts by thin-layer thermal insulation (ed.) [Letter to the editor]. Tribology letters, 66(4), 1-1
Open this publication in new window or tab >>Correction to: Friction reduction in elastohydrodynamic contacts by thin-layer thermal insulation
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2018 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, no 4, p. 1-1Article in journal, Letter (Refereed) Published
Abstract [en]

The original version of this article unfortunately contained a mistake. The correct information is given below. [ABSTRACT FROM AUTHOR]  Copyright of Tribology Letters is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-71140 (URN)10.1007/s11249-018-1079-x (DOI)
Available from: 2018-10-08 Created: 2018-10-08 Last updated: 2018-10-08Bibliographically approved
Wu, J., Huang, X., Berglund, K., Lu, X., Feng, X., Larsson, R. & Shi, Y. (2018). CuO nanosheets produced in graphene oxide solution: An excellent anti-wear additive for self-lubricating polymer composites. Composites Science And Technology, 162, 86-92
Open this publication in new window or tab >>CuO nanosheets produced in graphene oxide solution: An excellent anti-wear additive for self-lubricating polymer composites
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2018 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 162, p. 86-92Article in journal (Refereed) Published
Abstract [en]

In the present work, graphene oxide is used as template to produce CuO nanosheets, which solves aggregation and dispersion problems of CuO nanosheets resulting in improved lubricating performance. SEM and AFM studies show that CuO nanosheets are present in fusiform flake shape with a thickness, width and length of around 13, 400 and 1000 nm, respectively. CuO nanosheets were added to the carbon fibers reinforced Polytetrafluoroethylene (CF/PTFE) to study their lubricating performance. It is interesting, from fractured surfaces of composites, to find that CuO nanosheets enhance the interface properties between carbon fibers and PTFE. The wear resistance property of CF/PTFE is remarkably improved after filling CuO nanosheets. For example, the wear rate is reduced by 51% after filling 1.5 wt % CuO nanosheets. The wear resistance improvement effect of CuO nanosheets is much better than that of commercial CuO nanogranules and CuO nanorods. Worn surfaces and counter-surfaces studying indicates that CuO nanosheets can not only prevent the rubbed-off of PTFE or the detachment of CF, but also improve the properties of transfer films, which greatly reduce the adhesive wear and abrasive wear.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-68387 (URN)10.1016/j.compscitech.2018.04.020 (DOI)000438180500010 ()2-s2.0-85046114065 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-05-09 (andbra)

Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2018-08-09Bibliographically approved
Hultqvist, T., Shirzadegan, M., Vrček, A., Baubet, Y., Prakash, B., Marklund, P. & Larsson, R. (2018). Elastohydrodynamic lubrication for the finite line contact under transient loading conditions. Tribology International, 127, 489-499
Open this publication in new window or tab >>Elastohydrodynamic lubrication for the finite line contact under transient loading conditions
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2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 127, p. 489-499Article in journal (Refereed) Published
Abstract [en]

Research related to elastohydrodynamic lubrication (EHL) has led to improved performance and durability of machine elements where non-conformal contact geometries interact. Only a relatively small portion of the EHL literature has, however, dealt with the lubricating performance of finite line contacts under non-steady conditions, commonly found in many practical applications. The purpose of this work has thus been to further understand the behaviour of finite line EHL contacts under transient conditions by studying a finite length roller subjected to a time varying load using a full-system finite element approach. The transient load was shown to initiate oscillations in the system, governed by waves of lubricant moving through the contact, affecting both pressure and film thickness throughout the contact.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Elastohydrodynamic lubrication, Finite line contacts, Transient loading, Finite elements
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-70211 (URN)10.1016/j.triboint.2018.06.035 (DOI)000442334100048 ()2-s2.0-85049452630 (Scopus ID)
Funder
Swedish Energy Agency, 41215-1
Note

Validerad;2018;Nivå 2;2018-08-06 (andbra)

Available from: 2018-08-06 Created: 2018-08-06 Last updated: 2018-09-10Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9110-2819

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