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Friction in Elastohydrodynamic Lubrication
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today, with increasing demands on industry to reduce energy consumption and emissions, the strive to increase the efficiency of machine components is maybe bigger than ever. This PhD thesis focus on friction in elastohydrodynamic lubrication (EHL), found in, among others, gears, bearings and cam followers. Friction in such contacts is governed by a complex interaction of material, surface and lubricant parameters as well as operating conditions. In this work, experimental studies have been conducted that show how friction varies over a wide range of running conditions when changing parameters like lubricant viscosity, base oil type, surface roughness and lubricant temperature. These measurements have also been used to predict the friction behaviour in a real gear application. Numerical modeling of elastohydrodynamic (EHD) friction and film thickness are important for increased understanding of the field of EHL. Due to the high pressure and shear normally found in EHD contacts it is crucial that appropriate rheological models are used. An investigation has been carried out in order to assess the friction prediction capabilities of some of the most well founded rheological models. A numerical model was used to predict friction coefficients through the use of lubricant transport properties. Experiments were then performed that matches the predicted results rather well, and the deviations are discussed. The numerical model in combination with experimental measurements are used to investigate the friction reducing effect of diamond like carbon (DLC) coatings in EHL. A new mechanism of friction reduction through thermal insulation is proposed as an alternative to the current hypothesis of solid-liquid slip. These findings opens up for new families of coatings where thermal properties are in focus that may be both cheaper, and more effective in reducing friction in certain applications than DLC coatings of today.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2014. , 290 p.
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Research subject
Machine Elements
URN: urn:nbn:se:ltu:diva-17478Local ID: 38f483ca-704f-452a-ad7b-04227026aa99ISBN: 978-91-7439-999-8 (print)ISBN: 978-91-7583-000-1 (electronic)OAI: diva2:990483
Godkänd; 2014; 20140825 (marbjo); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Marcus Björling Ämne: Maskinelement/Machine Elements Avhandling: Friction in Elastohydrodynamic Lubrication Opponent: Professor H P Evans, Cardiff School of Engineering, Cardiff University, Cardiff, Wales, UK Ordförande: Professor Roland Larsson, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 2 oktober 2014, kl 09.00 Plats: E231, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29Bibliographically approved

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