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Krishna, V. V., Jobstfinke, D., Melzi, S. & Berg, M. (2020). An integrated numerical framework to investigate the running safety of overlong freight trains. Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit
Open this publication in new window or tab >>An integrated numerical framework to investigate the running safety of overlong freight trains
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.

Keywords
Longitudinal train dynamics, pneumatic braking, in-train forces, longitudinal compressive forces, long trains, multibody simulation
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Fordonsteknik
Identifiers
urn:nbn:se:kth:diva-268638 (URN)10.1177/0954409720905203 (DOI)
Funder
EU, Horizon 2020, 730811
Available from: 2020-02-19 Created: 2020-02-19 Last updated: 2020-02-20
Andersson, E., Berg, M., Nelldal, B.-L. & Stichel, S. (2020). Varför behövs Nya Stambanor i Sverige?. Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Varför behövs Nya Stambanor i Sverige?
2020 (Swedish)Report (Other academic)
Abstract [sv]

Stora investeringar och omdaningar planeras i vårt transportsystem. Transporterna väntas öka starkt i framtiden och mera kapacitet måste skapas på ett hållbart sätt. Diskussionerna om vilka transportmedel som ska prioriteras, såväl som vilka objekt som vi ska satsa på, är livliga.

En viktig fråga är satsningen på Nya Stambanor avsedda för snabba persontransporter i de redan idag hårt belastade stråken Stockholm‒Göteborg och Stockholm‒Malmö, med ett stort antal mellanliggande orter. Denna typ av järnvägar finns redan eller planeras i de flesta av världens ledande ekonomier. Syftet med att bygga nya stambanor är att öka den totala kapaciteten för person- och godstrafik på järnväg, öka punktligheten och öka tillgängligheten genom korta restider. Det ger också förutsättningar för större regionala arbetsmarknader och ökat bostadsbyggande utanför storstäderna samt en bättre miljö. Nuvarande stambanor avlastas och lämnar plats för bl a effektivare godstransporter.

Denna rapport behandlar först järnvägens egenskaper. Järnvägen är det energieffektivaste transportmedel vi känner till, den tar liten plats och är mycket trafiksäker. Moderna tåg på modern bana är vårt snabbaste transportmedel till lands. Tåg kan bereda plats och komfort för arbete och avkoppling under resan. Enligt författarnas uppfattning bör dessa egenskaper göra järnvägen till ett förstahandsalternativ för effektiva och hållbara transporter i de segment där järnvägen är eller kan bli konkurrenskraftig.

Prognoser och analys, samt erfaren­heter från utlandet, visar att trafikunderlaget i Sverige är tillräckligt för nya stambanor. Med de förslagna banorna väntas järnvägens totala kapacitet öka till mer än det dubbla i de mest belastade stråken. En viktig faktor är att den snabba och långsamma tågtrafiken separeras. Denna åtgärd ger ökad kapacitet, utöver vad de dubblerade spåren ger, eftersom tågen kan köra tätare efter varandra och störningarna i tågtrafiken minskar.

Restiderna för orterna längs de nya stambanorna minskar kraftigt, i regel mellan 30 och 65%. Tillsammans med ökad turtäthet och minskade störningar ger det stora ökningar av tågtrafiken. De officiella prognoserna lider dock av ett antal allvarliga brister, varför både trafikökningen och den samhällsekonomiska lönsamheten beräkningsmässigt framstår som mindre än vad den enligt KTH:s prognoser och internationell erfarenhet borde vara.

Författarna anser att anläggningskostnaderna är rimliga i relation till nyttorna och jämfört med vad andra omställningar i samhällets transportsystem kostar. Detsamma gäller den engångs ”klimatskuld” som uppkommer vid de flesta satsningar för framtiden inom alla trafikslag. Nya transportslag i ett tidigt utvecklingsskede (elflyg, magnettåg, Hyperloop etc) är mycket osäkra beträffande när eller om de överhuvudtaget kommer att bli tillgängliga för användning i stor skala. I flera fall skulle krävas stora tekniska genombrott som vi idag inte känner till. Vi anser att man rimligen inte idag kan besluta att satsa på helt nya tekniska system för vilka framtiden är mycket osäker. Vi kan inte heller ”vänta och se”, eftersom ytterligare kapacitet behövs redan idag och ledtiderna är långa.

Sammanfattningsvis är de nya stambanorna ett samhällsbyggnadsprojekt och en del i transportsektorns nödvändiga omställning. De ger korta restider och effektiva transporter mellan våra största städer, liksom till och från ett stort antal mellanliggande orter, med omnejd. Godstransporterna kan också få plats på spåren och de kan utvecklas och effektiviseras. Det handlar om hållbar mobilitet för människor och gods i framtiden.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. p. 24
Series
KTH Railway Group publications ; 20-01
Keywords
Järnväg, stambana, snabbtåg, höghastighetståg, kapacitet, hållbar utveckling
National Category
Transport Systems and Logistics
Research subject
Järnvägsgruppen - Effektiva tågsystem för persontrafik
Identifiers
urn:nbn:se:kth:diva-267214 (URN)978-91-7873-438-2 (ISBN)
Note

QC 20200205

Available from: 2020-02-04 Created: 2020-02-04 Last updated: 2020-02-05Bibliographically approved
Karis, T., Berg, M. & Stichel, S. (2019). Analysing the correlation between vehicle responses and track irregularities using dynamic simulations and measurements. Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit
Open this publication in new window or tab >>Analysing the correlation between vehicle responses and track irregularities using dynamic simulations and measurements
2019 (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]

Track irregularities play a key role in vehicle response, but it is not uncommon to find irregularities with similar statistical characteristics giving very different vehicle behaviour. It is therefore important to find a consistent way of describing track irregularities, which better matches the vehicle behaviour to facilitate an efficient track maintenance and vehicle acceptance testing. Various proposals have been made to resolve this issue, although with limited success. In the present paper, a methodology to break down the track–vehicle interaction into steps, by analysing the irregularity–response correlation in detail, is applied to both the measured and simulated data of a passenger coach. The results show a very good agreement and a high correlation coefficient between the vertical axle box acceleration and the second spatial derivative of the vertical track irregularities when analysing the simulated data, but not for the measured data. Parameter variations are carried out through simulations, in which the vertical track stiffness, vehicle unsprung mass, vertical primary suspension and different combinations of track irregularities are varied. The results show that track stiffness mainly affects the axle box acceleration whereas the primary vertical suspension stiffness and unsprung mass predominantly affect the vertical wheel–rail forces. Therefore, it is important to understand the influence of track stiffness, especially with the help of the measured data, and the methods that reduce its influence should be investigated in future works.

Place, publisher, year, edition, pages
Sage Publications, 2019
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-248967 (URN)10.1177/0954409719840450 (DOI)000503281700005 ()2-s2.0-85064008486 (Scopus ID)
Note

QC 20190507. QC 20200110

Available from: 2019-04-10 Created: 2019-04-10 Last updated: 2020-01-10Bibliographically approved
Mandal, N. K., Spiryagin, M., Berg, M. & Stichel, S. (2019). On the railhead material damage of insulated rail joints: Is it by ratchetting or alternating plasticity?. International Journal of Fatigue, 128, Article ID 105197.
Open this publication in new window or tab >>On the railhead material damage of insulated rail joints: Is it by ratchetting or alternating plasticity?
2019 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 128, article id 105197Article in journal (Refereed) Published
Abstract [en]

Railhead becomes severely stressed due to localised contact loadings. This is more critical in the vicinity of endposts of an insulated rail joint. Popular IRJ endpost materials are fibreglass (fb), polytetrafluoroethylene (ptfe) and nylon66 (ny). A 3D finite element analysis is carried out to study stress distributions in railhead material near the endposts. The progressive damage parameter, von Mises stress and other residual stress and strain plots indicate that plastic deformation and material degradation occur at sub-surface levels of the railhead material. Although fb and ptfe are better endpost materials than ny, ny displays superior performance over the other two.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2019
Keywords
FEA, Wheel/rail contact, Rail Joints, Fatigue damage, Endpost materials
National Category
Applied Mechanics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-260987 (URN)10.1016/j.ijfatigue.2019.105197 (DOI)000484647400020 ()
Note

QC 20191010

Available from: 2019-10-10 Created: 2019-10-10 Last updated: 2019-11-26Bibliographically approved
Krishna, V. V., Berg, M. & Stichel, S. (2019). Tolerable longitudinal forces for freight trains in tight S-curves using three-dimensional multi-body simulations. Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit
Open this publication in new window or tab >>Tolerable longitudinal forces for freight trains in tight S-curves using three-dimensional multi-body simulations
2019 (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]

With the need for increasing length of freight trains, Longitudinal Train Dynamics (LTD) and its influence on the running safety becomes a key issue. LTD is a complex issue with contributions from both the vehicles and the operating conditions such as infrastructure design, braking regimes, etc. Standards such as the UIC Code 530-2 and EN-15839 detail the procedure for on-track propelling tests that should be conducted to determine the running safety of a single wagon. Also, it only considers a single S-curve and specifies neighbouring wagons and buffers. The resulting LTD would hence not be able to judge the effects of various heterogeneities in the train formation such as the adjacent wagons, buffer types, carbody torsional stiffnesses, curvatures, etc. Here, there is a potential of using three-dimensional multi-body simulations to develop a methodology to judge the running safety of a train with regards to its longitudinal dynamic behaviour, subjected to various heterogeneities. A tool based on three-dimensional multi-body simulations has been developed to provide Longitudinal Compressive Force (LCF) limits, tolerable LCF for wagon combinations passing through S-curves of varying curvatures and assess the sensitivities of the various heterogeneities present in the train. The methodology is applied to open wagons of the ‘Falns’ type on tight S-curves by calculating the corresponding tolerable LCF and the effect of various parameters on the same is discussed.

Place, publisher, year, edition, pages
Sage Publications, 2019
Keywords
S-curve; longitudinal train dynamics; freight wagons; longitudinal compressive forces; multi-body simulation; tolerable force; derailment.
National Category
Vehicle Engineering
Research subject
Järnvägsgruppen - Fordonsteknik
Identifiers
urn:nbn:se:kth:diva-250776 (URN)10.1177/0954409719841794 (DOI)2-s2.0-85064678218 (Scopus ID)
Funder
EU, Horizon 2020, 730811
Note

QC 20190520

Available from: 2019-05-06 Created: 2019-05-06 Last updated: 2019-10-23Bibliographically approved
Karis, T., Berg, M., Stichel, S., Li, M., Thomas, D. & Dirks, B. (2018). Correlation of track irregularities and vehicle responses based on measured data. In: Spiryagin, M Gordon, T Cole, C McSweeney, T (Ed.), The Dynamics of Vehicles on Roads and Tracks, Vol 2: . Paper presented at 25th Symposium of the International Association of Vehicle System Dynamics, IAVSD 2017; Rockhampton; Australia; 14 August 2017 through 18 August 2017 (pp. 1285-1290). CRC Press/Balkema, 2
Open this publication in new window or tab >>Correlation of track irregularities and vehicle responses based on measured data
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2018 (English)In: The Dynamics of Vehicles on Roads and Tracks, Vol 2 / [ed] Spiryagin, M Gordon, T Cole, C McSweeney, T, CRC Press/Balkema , 2018, Vol. 2, p. 1285-1290Conference paper, Published paper (Refereed)
Abstract [en]

Track geometry quality and dynamic vehicle response are closely related, but do not always correspond with each other in terms of maximum values and standard deviations. This can often be seen to give poor results in analyses with correlation coefficients or regression analysis. Measured data from the EU project DynoTRAIN is used in this paper to evaluate track-vehicle response. A single degree of freedom model is used as inspiration to divide track-vehicle interaction into three parts, which are analysed in terms of correlation. One part, the vertical axle box acceleration divided by vehicle speed squared (z(w)/v(2)) and the second spatial derivative of the vertical track irregularities (z(t)''), is shown to be the weak link with lower correlation coefficients than the other parts. Future efforts should therefore be directed towards investigating the relation between axle box accelerations and track irregularity second derivatives, while also including more vehicles.

Place, publisher, year, edition, pages
CRC Press/Balkema, 2018
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-252948 (URN)000468325100124 ()2-s2.0-85061540737 (Scopus ID)9781138035713 (ISBN)
Conference
25th Symposium of the International Association of Vehicle System Dynamics, IAVSD 2017; Rockhampton; Australia; 14 August 2017 through 18 August 2017
Note

QC 20190611

Available from: 2019-06-11 Created: 2019-06-11 Last updated: 2019-06-11Bibliographically approved
Karis, T., Berg, M., Stichel, S., Li, M., Thomas, D. & Dirks, B. (2018). Correlation of track irregularities and vehicle responses based on measured data. Vehicle System Dynamics, 56(6), 967-981
Open this publication in new window or tab >>Correlation of track irregularities and vehicle responses based on measured data
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2018 (English)In: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 56, no 6, p. 967-981Article in journal (Refereed) Published
Abstract [en]

Track geometry quality and dynamic vehicle response are closely related, but do not always correspond with each other in terms of maximum values and standard deviations. This can often be seen to give poor results in analyses with correlation coefficients or regression analysis. Measured data from both the EU project DynoTRAIN and the Swedish Green Train (Gröna Tåget) research programme is used in this paper to evaluate track–vehicle response for three vehicles. A single degree of freedom model is used as an inspiration to divide track–vehicle interaction into three parts, which are analysed in terms of correlation. One part, the vertical axle box acceleration divided by vehicle speed squared ((Formula presented.)) and the second spatial derivative of the vertical track irregularities ((Formula presented.)), is shown to be the weak link with lower correlation coefficients than the other parts. Future efforts should therefore be directed towards investigating the relation between axle box accelerations and track irregularity second derivatives.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
Keywords
Wheel–rail force, axle box acceleration, track irregularities, vehicle response, dynoTRAIN, Green train, gröna tåget
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-228004 (URN)10.1080/00423114.2017.1403634 (DOI)000428600600006 ()2-s2.0-85034829859 (Scopus ID)
Note

QC 20180517

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2019-09-20Bibliographically approved
Marsilla, M., Berg, M., Krishna, V. V., Jobstfinke, D., Melzi, S. & Gisbert, R. (2018). D3.2 – Safety precautions in train configuration and brake application.
Open this publication in new window or tab >>D3.2 – Safety precautions in train configuration and brake application
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2018 (English)Report (Other academic)
Abstract [en]

For extensive rail freight transportation, one action to improve its capacity and efficiencyis to run long trains. From an European perspective this typically means running freight trains longer than 800-900 m. However, there are technical challenges associated with long-train operation.During traction (acceleration) the longitudinal tensile coupler forces can be significant, in particular if all locomotives are positioned in the front of the train. This might cause coupler breakage and thus loss of train integrity and safety risks.During braking (retardation) the longitudinal compressive coupler forces can become very large, especially when the braking is applied only from the front and when the braking signal is propagating slowly by the pneumatics through the main braking pipe. This issue is further emphasized when payload-dependent braking devices of the wagons do not fully match the payloads in question and when the brake blocks are of different materials. The large compressive forces may cause derailment when the train negotiates curves, in particular tight S-curves with radii such as 150 m, 170 m, etc.DYNAFREIGHT WP3 is devoted to different aspects of operation of long freight trains. In particular Task 3.1 and the present task, Task 3.2, are closely related assuming that the locomotives of the trains are not physically connected but use radio communication. It is also assumed that the traditional (P) UIC braking pneumatic system is used, thus electrically controlled pneumatic (ECP) braking is not introduced. Moreover, all couplers are assumed to consist of side buffers and central screw couplers.The work in these two DYNAFREIGHT tasks is carried out in collaboration with that of WP5 in the Shift2Rail member project Future Freight Locomotive for Europe (FFL4E). This joint work can be seen as a continuation of the work in the European project MARATHON in which some of the DYNAFREIGHT WP3 partners participated.Given the specifications defined in Task 3.1 of radio communication and traction&braking scenarios of long-train operation, the objective of Task 3.2 is to address the challenges indicated above and provide safety precautions when operating long freight trains. The Task 3.2 work rests on simulations, verified by measurements, and are split in three parts: braking pneumatics, 1D longitudinal dynamics and 3D derailment risk analysis. The pneumatics result is an important input to the 1D simulations, whose result in terms of longitudinal compressive forces (LCFs) is compared with tolerable LCFs found in the 3D analysis.In this D3.2 report Chapter 2 describes in more detail the simulation methodology adopted, the simulation tools that have been further devloped and some verifications against measurements. The first application, suggested by the FFL4E WP5 partners and consisting of an existing coal train operation with two locomotives (front+rear), is thensimulated in Chapter 3. In Chapter 4 longer and more heterogeneous freight trains are 

studied with the second locomotive at different positions. Some simulations have alsobeen carried out with three locomotives assuming that the second and third locomotives give identical traction/braking commands, see Chapter 4.Last but not least, Chapter 5 gives guidelines for long-train operation with respect to safety precautions in train configurations (locomotive positions, wagon types, coupler performance, brake block material, payloads), traction and braking scenarios, and tracklayout (gradients, horizontal curves).

Publisher
p. 206
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-261377 (URN)
Projects
DYNAFREIGHT (Shift2Rail Grant no. 730811)
Funder
EU, Horizon 2020, 730811
Note

QC 20191008

Available from: 2019-10-04 Created: 2019-10-04 Last updated: 2019-10-08Bibliographically approved
Pintado, P., Ramiro, C., Berg, M., Morales, A. L., Nieto, A. J., Chicharro, J. M., . . . Garcia, E. (2018). On the mechanical behavior of rubber springs for high speed rail vehicles. Journal of Vibration and Control, 24(20), 4676-4688
Open this publication in new window or tab >>On the mechanical behavior of rubber springs for high speed rail vehicles
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2018 (English)In: Journal of Vibration and Control, ISSN 1077-5463, E-ISSN 1741-2986, Vol. 24, no 20, p. 4676-4688Article in journal (Refereed) Published
Abstract [en]

There are many engineering design problems that call for rubber components as the best solution. Vulcanized rubber has found its way into all sorts of devices, from the universal automobile pneumatic tire to the ubiquitous compliant bushing. Some high-speed rail vehicle suspensions make use of rubber, not only in the air spring itself, but also in the auxiliary spring. The mechanical characteristics of this component influence vehicle dynamics and, therefore, accurate spring models with which to conduct dynamic analysis would make for powerful design tools. Nevertheless, the mechanical behavior of rubber defies simple modeling on account of stress relaxation, creep, set, viscosity, internal friction, and nonlinear stress-strain relations. Despite the advances in the micromechanical understanding of these phenomena, as well as in the macroscopic modeling of rubber spring behavior, there is ample room for refinement, and this is precisely the goal of this paper. The mechanical behavior of a particular rubber spring for high speed rail vehicles has been characterized. The results reveal the necessary components of the model, and suggest the appropriate procedure for parameter extraction. Our model proposal consists of three elements in parallel: a nonlinear elastic spring; a soft friction element; and a Maxwell viscous component. The characterization procedure takes into account both stress relaxation and nonlinear elasticity. The proposed model accurately reproduces experimental results and may then be used with confidence in any type of numerical simulation. Nevertheless, for this statement to be true, the problem of numerical softening potentially induced by soft friction models should be resolved. The paper will show that a trailing moving average filter, seamlessly tied to the model, wipes out the softening effect.

Place, publisher, year, edition, pages
Sage Publications, 2018
Keywords
Rubber springs, force relaxation, creep, smooth friction, viscosity, characterization, simulation
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-235999 (URN)10.1177/1077546317732206 (DOI)000445778100003 ()2-s2.0-85045298605 (Scopus ID)
Note

QC 20181016

Available from: 2018-10-16 Created: 2018-10-16 Last updated: 2018-10-16Bibliographically approved
Stichel, S., Casanueva, C., Berg, M. & Hossein Nia, S. (2018). Wear and RCF prediction based on improved contact mechanics modelling. In: : . Paper presented at 11th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, CM 2018; Delft; Netherlands; 24-27 September 2018.
Open this publication in new window or tab >>Wear and RCF prediction based on improved contact mechanics modelling
2018 (English)Conference paper, Oral presentation with published abstract (Other academic)
Keywords
wheel-rail contact, RCF, wear
National Category
Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-245040 (URN)
Conference
11th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, CM 2018; Delft; Netherlands; 24-27 September 2018
Note

QC 20190305

Available from: 2019-03-05 Created: 2019-03-05 Last updated: 2019-03-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2571-4662

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