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Open System Tribology and Influence of Weather Condition
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).ORCID iD: 0000-0001-7560-6232
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). (SYSTEM- O KOMPONENTDESIGN)ORCID iD: 0000-0003-4447-3363
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). (SYSTEM- O KOMPONENTDESIGN)ORCID iD: 0000-0003-2489-0688
2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 32455Article in journal (Refereed) Published
Abstract [en]

The tribology of an open system at temperatures ranging between 3 degrees C and -35 degrees C, with and without snow, was investigated using a pin-on-disc tribometer mounted in a temperature-controlled environmental chamber. The relationship between the microstructure and ductility of the materials and the tribology at the contacting surfaces was investigated. The study shows that during continuous sliding, pressure causes snow particles to melt into a liquid-like layer, encouraging the generation of oxide flakes on the contact path. The friction coefficient and wear rate are dramatically reduced through an oxidative friction and wear mechanism. In the absence of snow, the tribological process is controlled by the low temperature brittleness of steel in the temperature range from 3 degrees C to -15 degrees C. At these temperatures, cracks are prone to form and extend on the worn surfaces, resulting in the spalling of bulk scraps, which are crushed into debris that increases the friction coefficient and wear rate due to strong abrasion. When the temperature falls to -25 degrees C, an ice layer condenses on the metal surfaces and relaxes the tribological process in the same way as the added snow particles, which significantly decreases the friction and wear.

Place, publisher, year, edition, pages
Nature Publishing Group, 2016. Vol. 6, article id 32455
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-192723DOI: 10.1038/srep32455ISI: 000382158800001PubMedID: 27573973Scopus ID: 2-s2.0-84984843708OAI: oai:DiVA.org:kth-192723DiVA, id: diva2:974455
Note

QC 20160926

Available from: 2016-09-26 Created: 2016-09-20 Last updated: 2018-04-03Bibliographically approved
In thesis
1. Railway Open System Tribology
Open this publication in new window or tab >>Railway Open System Tribology
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Tribology in the railway system is of increasing interest in the new railway era due to the demand for higher speed and load capacity. Since railway vehicles operate in an open environment, their performance depends greatly on temperature, humidity and natural and artificial contaminants. Meanwhile, the “feedback” of railway vehicles to the surroundings, such as noise and airborne particles, is of great importance to the human health and the environment. Therefore, this thesis aims to investigate the strong interaction between railway tribology and the open environment. The effects of temperatures from -35 °C to 20 °C, relative humidity from 40% to 85%, natural contaminants such as ice particles on friction, wear, noise and airborne particle emissions at the wheel–rail and wheel–block brake contacts have been investigated in both lab- and full-scale contexts.

Papers A and B investigated the effect of temperature, humidity and ice particles on the friction and wear at unoxidized and oxidized wheel–rail contacts. The results indicate that increasing humidity reduces the wear at unoxidized contacts. A decrease in temperature tends to intensify the wear until an ice layer has condensed on the wheel and rail surfaces at -25 °C. Ice particles encourage the generation of oxide flakes at the contacting path, largely inhibiting the wear process.

Paper C, which was a lab-scale test, studied the friction, wear and noise generation from pre-oxidized wheel–rail contact with varied surface features. Major results include that the wear regime transition from mild wear to severe wear is always accompanied by an increase in noise level of 10 dB and a broader bandwidth of noise.

Paper D was a validation of the major findings of paper C in a full-scale test, which also saw an increase in noise level as well as a broader bandwidth when the wheel–rail contact transformed from mild to severe wear.

Paper E studied the effect of humidity on the friction, wear and airborne particle emissions of three railway brake-block materials. The results show that cast iron generated the highest friction coefficient, wear and particle emission, and organic composite the lowest levels.

Paper F conducted a thorough literature review on the open system tribology at the wheel–rail contact. Commonly seen parameters such as temperature, humidity and natural and artificial contaminants on friction, wear, noise and particle emissions were investigated.

Abstract [sv]

Järnvägsfordonen arbetar i en öppen miljö, vars prestanda och livslängd i form av friktion och nötning beror på temperatur, luftfuktighet samt naturliga och konstgjorda föroreningar. Samtidigt är återkopplingen, som järnvägsfordon ger till omgivningen i form av buller och luftburna partiklar, av stor betydelse för människors hälsa. Därför är målsättningen med denna avhandling att undersöka den starka samverkan som finns mellan järnvägsfordon och den öppna miljön.

Effekten av, temperaturer från -35 °C till 20 °C, relativ fuktighet från 40 % till 85 % och naturliga föroreningar som snö, på friktion, slitage, buller och luftburna partikelutsläpp vid hjulräls- och hjulblockbromskontakter har undersökts, både i laboratorier och i full skala.

Manuskript A och B undersökte effekten av temperatur, luftfuktighet och snö på friktionen och nötning vid oxiderade och icke-oxiderade hjulrälskontakter. Resultaten visar att en ökad luftfuktighet, minskar nötningen vid icke-oxiderade kontakter. Minskning av temperaturen tenderar att intensifiera nötningen, tills is kondenseras på hjul- och rälsytorna vid -25 °C. Iskristallerna, ökar hastigheten på genereringen av oxidflingor i kontakten, och förhindrar i stor utsträckning nötningsprocessen.

Manuskript C, som är ett laboratorieprov, studerade friktionen, nötningen och ljudgenerering från föroxiderade hjulrälskontakter med varierande yttopografi. Viktiga resultat, är att övergången, från mild nötning till svår nötning, alltid åtföljs av en ökad ljudnivå och en ökning av ljudets bandbredd.

Manuskript D är en fullskalevalidering av huvudresultatet från Manuskript C, vilket också uppvisade en ökning av ljudnivån om hjulrälskontakten gick från mild till svår nötning åtföljt av en ökning av ljudets bandbredd.

Manuskript E studerade effekten av luftfuktighet på friktion, nötning och luftburna nötningspartiklar av tre olika blockbromsmaterial. Resultaten visar att gjutjärn genererade den högsta friktionskoefficienten, nötningsnivån och halten av partikelutsläpp. Blockbromsar tillverkade av organisk komposit, uppvisade den lägsta nivån för alla tre uppmätta parametrar.

Manuskript F redovisar en litteraturgenomgång, hur det öppna systemet, påverkar tribologin i hjul-järnvägskontakten. Parametrar som temperatur, fuktighet, naturliga och konstgjorda föroreningar på friktion, slitage, buller och partikelutsläpp diskuterades i detalj.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 50
Series
TRITA-ITM-AVL ; 2018:6
Keyword
Wheel; Rail; Brake; Environmental conditions; Tribology; Noise; Particle, Hjul; Räl; Broms; Miljöförhållanden; Tribologi; Ljud; Partiklar
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-225339 (URN)978-91-7729-710-9 (ISBN)
Public defence
2018-04-27, Gladan, Brinellvägen 85, Stockholm, 11:04 (English)
Supervisors
Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2018-05-15Bibliographically approved

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