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Elastohydrodynamic lubrication for the finite line contact under transient loading conditions
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.ORCID iD: 0000-0002-7285-6639
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.ORCID iD: 0000-0003-2772-4861
SKF, Nieuwegein.
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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. Vol. 127, p. 489-499
Keywords [en]
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: urn:nbn:se:ltu:diva-70211DOI: 10.1016/j.triboint.2018.06.035ISI: 000442334100048Scopus ID: 2-s2.0-85049452630OAI: oai:DiVA.org:ltu-70211DiVA, id: diva2:1236834
Funder
Swedish Energy Agency, 41215-1
Note

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

For correction, see: Hultqvist T., Shirzadegan M., Vrcek A., Baubet Y., Prakash B., Marklund P., Larsson R. (2020). Corrigendum to “Elastohydrodynamic lubrication for the finite line contact under transient loading conditions” [Tribol Int 127 (2018) 489–499], Tribology International, vol 150, art 106414. doi: https://doi.org/10.1016/j.triboint.2020.106414

Available from: 2018-08-06 Created: 2018-08-06 Last updated: 2024-03-08Bibliographically approved
In thesis
1. Transient elastohydrodynamic lubrication: Effects of geometry, surface roughness, temperature, and plastic deformation
Open this publication in new window or tab >>Transient elastohydrodynamic lubrication: Effects of geometry, surface roughness, temperature, and plastic deformation
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The urgent need to reduce greenhouse gas emissions in combination with an increased use of sustainable energy resources have led to immense efforts on improving energy efficiency of mechanical systems. Consequently, modern machine elements are typically lubricated with low viscosity oils and designed to endure an increasingly high power density. This typically implies that the surfaces in contact are separated by thinner lubricant films that must carry higher loads. Thereby, in order to improve the durability and efficiency of future machine elements, an improved fundamental understanding of the predominant lubrication mechanisms must be achieved. This thesis concerns numerical simulation of non-conformal lubricated contacts where significant elastic deformations in combination with hydrodynamic effects govern the lubricating film formation, typically found in e.g., rolling element bearings, gears, and cam-follower systems. Such contacts relate to a lubrication regime known as elastohydrodynamic lubrication (EHL), which is often studied using simplifying assumptions due to its multiphysical nature. Typical simplifications of the EHL problem may include e.g., steady-state conditions, perfectly elastic surfaces, isothermal conditions, and Newtonian lubricant behaviour. However, such simplifications may be progressively relieved because of a continuously improved computer performance and the use of increasingly efficient numerical methods. In this work, time dependent simulations of EHL contacts are conducted with the purpose of improving the fundamental understanding of the predominant lubrication mechanisms. This is achieved by the development and utilisation of novel models and modelling techniques, specifically developed for the conducted investigations focusing on e.g., temperature, plastic deformation, surface roughness, and contact geometry. The developed models are all an extension of a full-system finite element modelling approach that was relatively recently introduced to the EHL community. Important findings from this work relate to the influence of transient fluctuations in EHL contacts, which occur due to both transient loads and moving surface roughness. It is shown that in the case of transient loading of a finite line EHL contact, a steady state assumption may overestimate the minimum film thickness and underestimate the maximum pressure over time due to the formation of lubricant waves travelling through the contact. Furthermore, thermal and non-Newtonian effects on viscosity may be necessary to consider in both qualitative and quantitative studies of roughness within the EHL contact, especially under sliding conditions and short wavelength roughness. Lastly, transient fluctuations related to the over-rolling of surface features are shown to potentially increase the pressure within the EHL contact to such an extent that plastic deformations of the contacting surfaces occur. The models established in this work may provide researchers and engineers with ways to improve their studies of transient EHL contacts. The salient findings from the conducted studies also open up for interesting directions that may be extended to potentially improve the lubrication theories currently in use and thereby improve the design of future machine elements that employ non-conformal contacts.

Place, publisher, year, edition, pages
Luleå University of Technology, 2020
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-78886 (URN)978-91-7790-603-2 (ISBN)978-91-7790-604-9 (ISBN)
Public defence
2020-09-25, E632, Luleå, 09:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, P41215-1
Available from: 2020-05-19 Created: 2020-05-15 Last updated: 2023-09-05Bibliographically approved

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Hultqvist, TobiasShirzadegan, MohammadVrček, AleksPrakash, BrahamMarklund, PärLarsson, Roland

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