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A wear tolerant slip-ring assembly, individual spring-wire brushes in a v-grooved metal-graphite ring
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Tribomaterial, Tribomaterials)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Tribomaterial, Tribomaterials)
2014 (English)In: Proceedings of the 27th International Conference on Electrical Contacts, VDE Verlag GMBH Berlin Offenbach , 2014, 237-243 p.Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
VDE Verlag GMBH Berlin Offenbach , 2014. 237-243 p.
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
URN: urn:nbn:se:uu:diva-239221OAI: oai:DiVA.org:uu-239221DiVA: diva2:773706
Conference
27th International Conference on Electrical Contacts, Dresden, Germany, June 22-26, 2014
Available from: 2014-12-19 Created: 2014-12-19 Last updated: 2017-12-15
In thesis
1. Tribology of Metal-Graphite Composites: A Study of Sliding Electrical Contact Surfaces
Open this publication in new window or tab >>Tribology of Metal-Graphite Composites: A Study of Sliding Electrical Contact Surfaces
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

An environmentally sustainable production of electrical power is important for preserving the earth’s natural resources. In order to utilize this power as efficiently as possible, it is of great importance to minimize the losses, for example in sliding electrical contacts. A sliding electrical contact is where current is transferred from one rotating to one stationary component and power is lost due to friction and contact resistance. Also in some signal applications, high performance sliding contacts are crucial to ensure stable signal transfer with low noise. Although sliding electrical contacts are primarily designed for good electrical performance, the system will benefit also from optimization of the tribological properties.

The aim of this thesis is to increase the fundamental knowledge of the tribological and electrical performance of metal-graphite composite materials for sliding electrical contacts. The influence of mechanical and electrical load was investigated. Different stationary materials, from pure copper to nanocomposite coatings, were tested against copper- and silver-graphites. Two complementary test setups were used, one with reciprocating and one with unidirectional sliding. Surface analysis was essential to gain deepened understanding of the influence of the interaction on the surfaces. Especially my novel imaging of cross-sections has advanced the level on knowledge in this research field.

On the stationary material surface, a tribofilm forms with constituents from the metal-graphite and the surrounding atmosphere. Cross-sectioning reveals a material flow that indicates turbulence. Furthermore, the presence of oxides in the tribofilm is not necessarily detrimental for the contact resistance as long as there is also pure metal available. The presence of graphite is vital for low friction and wear. It is shown that the tribological and electrical behaviour of this system is only marginally influenced by the material selection of the stationary contact. Increasing the metal content in the composite, on the other hand, greatly reduces the contact resistance while there is no significant impact on friction and wear. The mechanical load has to be optimized to compromise between low wear (achieved with low load) and low contact resistance (achieved with high load). Pure mechanical tests show a lower friction and higher wear rate in comparison to tests with a five ampere current.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 75 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1565
Keyword
tribology; tribofilm; surface analysis; wear; friction; electrical contacts; metal-graphite; contact resistance; cross-section; nanocomposite coating; copper; silver
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
urn:nbn:se:uu:diva-329860 (URN)978-91-513-0079-5 (ISBN)
Public defence
2017-11-10, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2017-10-20 Created: 2017-09-22 Last updated: 2017-10-30

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Grandin, MartinaWiklund, Urban

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