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Active friction control by using CO2 and moisture
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.ORCID-id: 0000-0001-8157-4644
2019 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Nowadays the demand for intelligent control of tribological interactions is strongly increasing in various applications. We often strive to minimize friction but there are also many situations where high friction is desirable. In some cases, something in between, i.e. optimum friction, is attractive. Driven by the broad application prospects, many controllable friction systems regulated with external stimuli such as solvent, pH, temperature, electric potential, and magnetic field have been designed and fabricated. When external stimuli are imposed on the smart materials, the macroscopic physicochemical properties of the materials are dramatically changed, making controllable friction behavior to become possible. However, most of these exploratory works are in nano/micro size and it’s difficult to use these incredible methods in macroscale directly due to that macroscopic laws of friction do not generally apply to nanoscale contacts. This thesis attempts to find more versatile methods of friction control and try to find the possibility to achieve friction control at macro-size.

Firstly, since viscosity plays an important role in elastohydrodynamic lubrication (EHL) at macro-size, it is instigated if it would be possible to adjust friction by controlling viscosity in a lubricated contact. By exploiting the ability to adjust the viscosity of the switchable ionic liquids, 1,8-Diazabicyclo (5.4.0) undec-7-ene (DBU)/ glycerol mixture via the addition of CO2, the friction could be controlled in the EHL regime (Paper Ⅰ). In order to understand more about the lubricating mechanism of DBU/glycerol/CO2 mixture, the central film thickness of the lubricants as a function of the entrainment speed was investigated.

Secondly, due to that adhesion could have influence on boundary lubrication (BL) friction at macro-size, it is investigated if it would be possible to adjust friction in a lubricated contact by controlling environmental humidity, which can alter the H-bond types, leading the change of adhesion. By exploiting the ability to adjust the environmental humidity by various saturated salt solutions, friction behavior lubricated by Choline L-Proline ([Cho][Pro]) could be modulated in a wide range of relative humidities (RH) (Paper Ⅱ).

Ort, förlag, år, upplaga, sidor
Luleå: Luleå tekniska universitet, 2019.
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Nyckelord [en]
friction control
Nationell ämneskategori
Tribologi (ytteknik omfattande friktion, nötning och smörjning)
Forskningsämne
Maskinelement
Identifikatorer
URN: urn:nbn:se:ltu:diva-76512ISBN: 978-91-7790-488-5 (tryckt)ISBN: 978-91-7790-489-2 (digital)OAI: oai:DiVA.org:ltu-76512DiVA, id: diva2:1365871
Presentation
2019-12-05, E231, Luleå uninversity of technology, Luleå, 16:29 (Engelska)
Opponent
Handledare
Tillgänglig från: 2019-10-28 Skapad: 2019-10-25 Senast uppdaterad: 2019-11-06Bibliografiskt granskad
Delarbeten
1. A smart friction control strategy enabled by CO2 absorption and desorption
Öppna denna publikation i ny flik eller fönster >>A smart friction control strategy enabled by CO2 absorption and desorption
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2019 (Engelska)Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, nr 1, artikel-id 13262Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Intelligent control of friction is an attractive but challenging topic and it has rarely been investigated for full size engineering applications. In this work, it is instigated if it would be possible to adjust friction by controlling viscosity in a lubricated contact. By exploiting the ability to adjust the viscosity of the switchable ionic liquids, 1,8-Diazabicyclo (5.4.0) undec-7-ene (DBU)/ glycerol mixture via the addition of CO2, the friction could be controlled in the elastohydrodynamic lubrication (EHL) regime. The friction decreased with increasing the amount of CO2 to the lubricant and increased after partial releasing CO2. As CO2 was absorbed by the liquid, the viscosity of the liquid increased which resulted in that the film thickness increased. At the same time the pressure-viscosity coefficient decreased with the addition of CO2. When CO2 was released again the friction increased and it was thus possible to control friction by adding or removing CO2.

Ort, förlag, år, upplaga, sidor
Springer, 2019
Nationell ämneskategori
Kemiska processer Tribologi (ytteknik omfattande friktion, nötning och smörjning)
Forskningsämne
Kemisk teknologi; Maskinelement
Identifikatorer
urn:nbn:se:ltu:diva-76046 (URN)10.1038/s41598-019-49864-w (DOI)000485680900059 ()31519987 (PubMedID)2-s2.0-85072208170 (Scopus ID)
Anmärkning

Validerad;2019;Nivå 2;2019-09-18 (johcin)

Tillgänglig från: 2019-09-18 Skapad: 2019-09-18 Senast uppdaterad: 2019-10-25Bibliografiskt granskad

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