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An integrated numerical framework to investigate the running safety of overlong freight trains
KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group. (Spårfordon)ORCID iD: 0000-0002-4477-971x
KTH, School of Engineering Sciences (SCI), Engineering Mechanics.ORCID iD: 0000-0002-2571-4662
2020 (English)In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017Article in journal (Refereed) Published
Abstract [en]

Long freight trains up to 1500 m in length are currently not in regular operation in Europe. One of the important reasons for the same is high inter-wagon forces generated during the operation, especially when pneumatic (P-type) brake systems are used. For long trains with multiple locomotives at different positions along the train, radio communication with necessary fail-safe mechanisms can be used to apply the brakes. Long freight train operation on a given line is subjected to various attributes such as braking/traction scenarios, loading patterns, wagon geometries, brake-block materials, buffer types, track design geometries, etc., which are referred to as heterogeneities. The complex longitudinal train dynamics arising in the train due to various heterogeneities play a major role in determining its running safety. In this context, the maximum in-train force refers to the maximum force developed between any two wagons along the train during operation. The tolerable longitudinal compressive force is the maximum compressive force that can be exerted on a wagon without resulting in its derailment. Here, the authors adopt a bottom-up approach to model pneumatic braking systems and inter-wagon interactions in multibody simulation environments to study the complex longitudinal train dynamics behavior and estimate maximum in-train forces and tolerable longitudinal compressive forces, subjected to various heterogeneities. These two force quantities intend to facilitate a given freight train operation by providing guidelines regarding the critical heterogeneities, that currently limit its safe operation. In doing so, the authors propose the notion to have an operation-based approval for long freight trains using the simulations-based tool.

Place, publisher, year, edition, pages
SAGE Publications , 2020.
Keywords [en]
Longitudinal train dynamics, pneumatic braking, in-train forces, longitudinal compressive forces, long trains, multibody simulation
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Fordonsteknik; Vehicle and Maritime Engineering; Järnvägsgruppen - Effektiva tågsystem för godstrafik
Identifiers
URN: urn:nbn:se:kth:diva-268638DOI: 10.1177/0954409720905203ISI: 000514530600001Scopus ID: 2-s2.0-85081658945OAI: oai:DiVA.org:kth-268638DiVA, id: diva2:1394460
Funder
EU, Horizon 2020, 730811
Note

QC 20200603

Available from: 2020-02-19 Created: 2020-02-19 Last updated: 2022-06-26Bibliographically approved
In thesis
1. Long freight trains and long-term rail surface damage
Open this publication in new window or tab >>Long freight trains and long-term rail surface damage
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Track damage due to progressively increasing tonnage, especially due to longer and heavier freight trains, is one of the major problems faced in the European rail sector. In this context, to stay competitive, optimal track maintenance practices, track-friendly vehicles and safe operations of long freight trains assume prominence.

This PhD thesis studies long freight train operations and the long-term rail surface damage that they cause, to build a computer simulation-based framework for maintenance planning and assessment of running safety. 

The framework is formulated with four parts: long freight train operations, vehicle dynamics, rail surface damage and track maintenance. This is followed by a literature survey on each of the subtopics and how they are linked to each other.Safe operation of long freight trains in infrastructure bottlenecks such as S-curves is studied using three-dimensional multi-body simulations. Based on this, guidelines to build long freight trains and driving scenarios that can keep longitudinal in-train forces within acceptable limits have been provided. 

Multi-body simulation models of various freight bogies, including a novel design, are built and their dynamic running behaviour studied according to EN standards. The key focus is on track-loading and to this effect, methodologies for simulations-based assessment of `track-friendliness' of various bogie designs are studied. Various approaches to quantify rail surface damage using multi-body simulations in the form of wear and Rolling Contact Fatigue (RCF) are studied. Based on this, measures to ascertain similarities and differences in results from different approaches have been put forward. 

The impact of track maintenance, in the form of periodic rail reprofiling activities in different networks, on the evolution of rail surface damage is studied. It is found that optimal maintenance planning can be tailored depending on the type of traffic on the network.

Finally, various parts of the framework have been brought together to form a `train-track interaction' approach to facilitate optimal maintenance planning.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022. p. 95
Series
TRITA-SCI-FOU ; 2022:01
Keywords
track friendliness; rail surface damage; multi-body simulation; longitudinal train dynamics; track maintenance; rolling contact fatigue, wear
National Category
Mechanical Engineering Vehicle Engineering Applied Mechanics
Research subject
Engineering Mechanics; Vehicle and Maritime Engineering; Järnvägsgruppen - Effektiva tågsystem för godstrafik
Identifiers
urn:nbn:se:kth:diva-307653 (URN)978-91-8040-130-2 (ISBN)
Public defence
2022-03-09, U1, Brinellvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
EU, Horizon 2020
Available from: 2022-02-07 Created: 2022-02-02 Last updated: 2022-06-25Bibliographically approved

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Krishna, Visakh VBerg, Mats

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