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An adhesion model for wheel-rail contact at the micro level using measured 3d surfaces
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.ORCID iD: 0000-0003-2489-0688
2014 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 314, no 1-2, 162-170 p.Article in journal (Refereed) Published
Abstract [en]

Railway vehicles require a certain level of wheel-rail adhesion for efficient, reliable, and economical operation. A comprehensive wheel-rail contact model is useful for optimizing the adhesion, to simulate vehicle running conditions and to predict wear and rolling contact fatigue. A new contact model using measured 3D surfaces has been developed, comprising normal contact, rolling-sliding contact, flash temperature, and local friction coefficient models. This model can predict the local contact pressure, including the plasticity, local flash temperature, local tangential stress, local friction coefficient, and global adhesion coefficient. The influence of surface topography, creep, and speed on the adhesion coefficient, real contact area, and contact temperature is discussed. Results indicate that, due to increased contact area, the adhesion coefficient decreases with increased surface roughness, although the change is small. Furthermore, increasing speed reduces the adhesion coefficient due to the increasing contact temperature.

Place, publisher, year, edition, pages
2014. Vol. 314, no 1-2, 162-170 p.
Keyword [en]
Adhesion, Contact temperature, Local friction coefficient, Measured 3D surfaces, Rolling-sliding contact, Wheel-rail
National Category
URN: urn:nbn:se:kth:diva-133357DOI: 10.1016/j.wear.2013.11.031ISI: 000337018100022ScopusID: 2-s2.0-84899104604OAI: diva2:660972

QC 20140520. Updated from manuscript to article.

Available from: 2013-10-31 Created: 2013-10-31 Last updated: 2014-07-03Bibliographically approved
In thesis
1. Adhesion in the wheel-rail contact
Open this publication in new window or tab >>Adhesion in the wheel-rail contact
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To attract more customers and compete with other modes of transportation, railway transport needs to ensure safety, punctuality, high comfort, and low cost; wheel–rail adhesion, i.e., the transmitted tangential force in the longitudinal direction during driving and braking, plays an important role in all these aspects. Adhesion needs to be kept at a certain level for railway operation and maintenance. However, wheel−rail contact is an open system contact. Different contaminants can present between the wheel and rail surfaces, forming a third-body layer that affects the adhesion. Prediction of wheel–rail adhesion is important for railway operations and research into vehicle dynamics; however, this prediction is difficult because of the presence of contaminants.

This thesis deals with wheel–rail adhesion from a tribological perspective. The five appended papers discuss wheel–rail adhesion in terms of dry conditions, lubricated conditions, leaf contamination, iron oxides, and environmental conditions. The research methodologies used are numerical modelling, scaled laboratory experiments, and field tests. The research objective is to understand the mechanisms of the adhesion loss phenomenon. 

A numerical model was developed to predict wheel–rail adhesion based on real measured 3D surfaces. Computer simulation indicates that surface topography has a larger impact on lubricated than on dry contacts. Plastic deformation in asperities is found to be very important in the model. Ball-on-disc tests indicate that water can give an extremely low adhesion coefficient on smooth surfaces, possibly due to surface oxidation. Investigation of lubricated contacts at low speed indicates that oil reduces the adhesion coefficient by carrying a normal load, while adhesion loss due to water depends on the surface topography, water temperature, and surface oxidation. A field investigation indicates that leaves reduce the friction coefficient because of the chemical reaction between leaves and bulk materials. The thickness of the surface oxide layer was found to be an essential factor determining adhesion reduction. Pin-on-disc experiments found a transition in the friction coefficient with regard to the relative humidity, due to a trade-off between the water molecule film and the hematite on the surface. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. 31 p.
Trita-MMK, ISSN 1400-1179 ; 2013:15
Adhesion, wheel-rail contact, contaminants, tribology
National Category
Research subject
The KTH Railway Group - Tribology
urn:nbn:se:kth:diva-133342 (URN)978-91-7501-896-6 (ISBN)
Public defence
2013-11-22, F3, Lindstedtsvägen 26, KTH, Stockholm, 09:00 (English)

QC 20131031

Available from: 2013-10-31 Created: 2013-10-30 Last updated: 2013-10-31Bibliographically approved

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