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  • 1.
    Andersson, Evert
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Greenhouse gas emissions from rail services: Present and future2010Inngår i: Proceedings of Railways and Environment, 2010Konferansepaper (Fagfellevurdert)
  • 2.
    Andersson, Evert
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Nelldal, Bo-Lennart
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Trafik och logistik. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Fröidh, Oskar
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Trafik och logistik. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    TOSCA. Rail freight transport: Techno-economic analysis of energy and greenhouse gas reductions2011Rapport (Annet vitenskapelig)
    Abstract [en]

    In Stage 1 of the EU/FP7-funded project TOSCA (Technology Opportunities and Strategies toward Climate-friendly trAnsport) the techno-economical feasibility of different technolo-gies and means to reduce greenhouse gas (GHG) emissions is being analysed for different modes of transport. This is made over the long-term perspective until 2050, with 2009 as the reference year. This is the report on the rail freight transport market, applicable to the European Union (EU-27).The analysis presented in this report estimates that a number of efficient technologies and means are available, individually and in combination, to significantly reduce energy use and the resulting GHG emissions on the rail freight market until 2050. The analysis has considered the following technologies and means:

    – heavy freight trains (high payload capacity per metre of train as well as longer trains)

    – eco-driving, including traffic flow management

    – energy recovery

    – high-efficiency machinery in locomotives and electric supply

    – low air drag

    – incremental improvements, in particular reduced tare mass of wagons.

    Despite anticipated higher train speeds in most future train operations the above-mentioned technologies and means have, according to the analysis, the potential to reduce the average energy use per net-tonne-km (tkm) of payload by 40–50 % until 2050. As a consequence also the direct and indirect GHG emissions will be reduced. Energy use and GHG emissions are measured per net-tonne-km, assuming representative load factors in different operations.

  • 3.
    Andersson, Evert
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Nelldal, Bo-Lennart
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Trafik och logistik. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Fröidh, Oskar
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Trafik och logistik. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    TOSCA. Rail passenger transport: Techno-economic analysis of energy and greenhouse gas reductions2011Rapport (Annet vitenskapelig)
    Abstract [en]

    In Stage 1 of the EU/FP7-funded project TOSCA (Technology Opportunities and Strategies toward Climate-friendly trAnsport) the techno-economical feasibility of different technologies and means to reduce greenhouse gas (GHG) emissions is being analysed for the different modes of transport. This is made in the long-term perspective until 2050, with 2009 as the reference year. This is the report on rail passenger transport, applicable to the European Union (EU-27).The present report has been subject to review among railway experts, representing train suppliers, railway operators as well as academia. They have also responded to a questionnaire. Further, a workshop was held, where the report with assumptions and results was discussed.In the analysis presented in this report it is estimated that a number of efficient improvements that, individually and in combination, are available in order to significantly reduce energy use and the resulting GHG emissions on the rail passenger market until 2050. The analysis has considered different technologies and means:

    – low air drag

    – low train mass

    – energy recovery

    – eco-driving, including traffic flow management

    – space efficiency in trains (increasing payload per metre of train)

    – incremental improvements of energy efficiency, in particular reduced losses.

    Despite anticipated higher average train speeds in the future these combined approaches will, according to the analysis, have the potential to reduce the average specific energy use per passenger-km (pkm) in the order of 45–50 % in the very long term until 2050. As a consequ-ence also the direct and indirect GHG emissions will be reduced. The highest reductions are possible in city and regional rail operations. Reductions are more limited in high-speed opera-tions, because of the advanced technologies already applied. However, high-speed rail has today a comparatively low energy use per passenger-km, partly due to its high average load factor. To be consistent with other work packages of TOSCA, energy use and GHG emissions are measured per passenger-km, assuming representative load factors in different operations.

  • 4.
    Andersson, Evert
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Casanueva, Carlos
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Rail Systems and Rail Vehicles: Part 2: Rail Vehicles2016 (oppl. 1)Bok (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    This compendium is mainly intended for MSc education in rail vehicle engineering at KTH Royal Institute of Technology, Stockholm, Sweden. The objective is to give an overview and fundamental knowledge of different rail systems, followed by a more thorough introduction to rail vehicles. In this way most rail aspects are covered. The compendium consists of 20 chapters.

  • 5.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Preface to special issue on the Green Train programme2014Inngår i: International Journal of Rail transportation, ISSN 2324-8378, E-ISSN 2324-8386, Vol. 2, nr 1Artikkel i tidsskrift (Fagfellevurdert)
  • 6.
    Berg, Mats
    KTH, Tidigare Institutioner, Farkostteknik.
    Understanding wear and profile changes of wheels and rails2004Inngår i: Proceedings of Conference on Advancing Practical Strategies for Wheel/Rail Interface Management, 2004Konferansepaper (Annet vitenskapelig)
  • 7.
    Berg, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Stensson Trigell, AnnikaKTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Selected and extended papers from the 21st symposium of the International Association of Vehicle System Dynamics: held at the Royal Institute of Technology (KTH), Stockholm, Sweden, August 17-21, 20092010Konferanseproceedings (Fagfellevurdert)
  • 8.
    Berg, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Stensson Trigell, AnnikaKTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Special Issue: State of the Art Papers of the 21st IAVSD Symposium2009Konferanseproceedings (Fagfellevurdert)
  • 9.
    Berggren, Eric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Simulation, Development and Field Testing of a Track StiffnessMeasurement Vehicle2005Inngår i: 8th Interntaional Heavy Haul Conference, Rio de Janeiro, 2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new vehicle for continuous measurement of vertical track stiffness has been built by Banverket. Two oscillatingmasses of the vehicle excite the track dynamically and the track stiffness is calculated from measured axle box forces andaccelerations. The stiffness is given as a complex quantity and presents both the magnitude and the phase. The repeatability isvery good, and some promising results for soft subsoils are shown. Both overall measurements at higher speeds (up to 60km/h) and detailed investigations (below 10 km/h) can be performed.

  • 10. Bhiwapurkar, M. K.
    et al.
    Saran, V. H.
    Goel, V. K.
    Mansfield, N.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Study of human comfort under thermal and vibratory environment using physiological indices2009Inngår i: 16th International Congress on Sound and Vibration 2009, ICSV 2009, 2009, s. 4376-4383Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Besides the vibrations, passenger discomfort is influenced by various other factors such as, the environmental factors of noise, temperature, humidity and visual stimuli, etc. The discomfort can be measured both subjectively and objectively. Rammohan25 studied the influence of backrest support and handgrip contractions on acute metabolic, respiratory, and cardiovascular responses during exposure to whole-body vibration (WBV). In the present work, discomfort of passengers subjected to whole body random vibrations, environmental factors such as temperature, humidity and noise level variations by assessing their effect on various physiological parameters like, Pulse Rate, Respiration Rate, Galvanic Skin Response, Skin Temperature, Heart Rate, Heart Rate Variability and ECG values has been studied. The study was conducted on the three axes vibration simulator developed in the Laboratory, IIT Roorkee, India as a mock-up of a railway vehicle. The simulator room has a controlled temperature and humidity environment and its noise level can also be controlled. A BIOPAC system was used for data acquisition along with various modules for measuring physiological parameters. The mean and standard deviation of physiological parameters, possibly indicating the human comfort or discomforts for the 12 subject is found out. The design of experiment (ANOVA) was employed to quantify the relationships between measured responses and the input factors. The results show that some physiological parameters viz, pulse rate, SKT and HR show variation in vibration condition at 0.6 m/s2. It is also found that all the parameters affected by noise level and temperature show significant variation between no vibration condition and vibration condition.

  • 11. Bhiwapurkar, M. K.
    et al.
    Saran, V. H.
    Harsha, S. P.
    Goel, V. K.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Effect of magnitudes and directions (mono-axis and multi-axis) of whole body-vibration exposures and subjects postures on the sketching performance2011Inngår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 225, nr F1, s. 71-83Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Whole-body vibrations in trains are known to affect the performance of sedentary activities such as reading, writing, sketching, working on a computer, etc. The objective of the study was to investigate the extent of disturbance perceived in sketching task by seated subjects in two postures under mono-and multi-axis Gaussian random vibration environment. The study involved 21 healthy male subjects in the age group of 23-32 years. Random vibrations were generated both in mono-and multi-axial directions in the frequency range of 1-10 Hz at 0.5, 1.0, and 1.5 m/s(2) rms (root mean square) amplitude. The subjects were required to sketch given geometric figures such as a circle, triangle, rectangle, and square with the help of ball-point pen under given vibration stimuli in two postures (sketch pad on lap and sketch pad on table). The deviation in distortion with respect to the given figure is represented in terms of percentage distortion. The influence of vibrations on the sketching activity was investigated both subjectively and by two specifically designed objective methods, namely, RMS (root mean square methodology) and area methods. The judgements of perceived difficulty to sketch were rated using seven-point semantic judgement scale. The percentage distortion and difficulty in sketching activity increased with an increase in vibration magnitude. Both subjective evaluation and the RMS method revealed that the task was affected more while sketching on the table. The percentage distortion was affected similarly and maximum in all the vibration directions except for the vertical, while sketching difficulty was found to be higher only with longitudinal and multi-axis vibration direction. The subjective evaluation also revealed that there was no effect of the type of entity chosen on the sketching difficulty.

  • 12. Bhiwapurkar, M. K.
    et al.
    Saran, V. H.
    Harsha, S. P.
    Goel, V. K.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Influence of Mono-axis Random Vibration on Reading Activity2010Inngår i: Industrial Health, ISSN 0019-8366, E-ISSN 1880-8026, Vol. 48, nr 5, s. 675-681Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent studies on train passengers' activities found that many passengers were engaged in some form of work, e.g., reading and writing, while traveling by train. A majority of the passengers reported that their activities were disturbed by vibrations or motions during traveling. A laboratory study was therefore set up to study how low-frequency random vibrations influence the difficulty to read. The study involved 18 healthy male subjects of 23 to 32 yr of age group. Random vibrations were applied in the frequency range (1-10 Hz) at 0.5, 1.0 and 1.5 m/s(2) rms amplitude along three directions (longitudinal, lateral and vertical). The effect of vibration on reading activity was investigated by giving a word chain in two different font types (Times New Roman and Anal) and three different sizes (10, 12 and 14 points) of font for each type. Subjects performed reading tasks under two sitting positions (with backrest support and leaning over a table). The judgments of perceived difficulty to read were rated using 7-point discomfort judging scale. The result shows that reading difficulty increases with increasing vibration magnitudes and found to be maximum in longitudinal direction, but with leaning over a table position. In comparison with Times New Roman type and sizes of font, subjects perceived less difficulty with Anal type for all font sizes under all vibration magnitude.

  • 13. Bruni, Stefano
    et al.
    Vinolas, Jordi
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Polach, Oldrich
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Modelling of suspension components in a rail vehicle dynamics context2011Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 49, nr 7, s. 1021-1072Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Suspension components play key roles in the running behaviour of rail vehicles, and therefore, mathematical models of suspension components are essential ingredients of railway vehicle multi-body models. The aims of this paper are to review existing models for railway vehicle suspension components and their use for railway vehicle dynamics multi-body simulations, to describe how model parameters can be defined and to discuss the required level of detail of component models in view of the accuracy expected from the overall simulation model. This paper also addresses track models in use for railway vehicle dynamics simulations, recognising their relevance as an indispensable component of the system simulation model. Finally, this paper reviews methods presently in use for the checking and validation of the simulation model.

  • 14.
    Burgelman, Nico
    et al.
    TU Delft.
    Sichani, Matin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Li, Zili
    TU Delft.
    Dollevoet, R
    TU Delft.
    Enblom, Roger
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Comparison of wheel/rail contact models applied for online vehicle dynamic simulation2013Konferansepaper (Fagfellevurdert)
  • 15. Burgelman, Nico
    et al.
    Sichani, Matin Sh
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Enblom, Roger
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Li, Zili
    Dollevoet, Rolf
    Influence of wheel-rail contact modelling on vehicle dynamic simulation2015Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 53, nr 8, s. 1190-1203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a comparison of four models of rolling contact used for online contact force evaluation in rail vehicle dynamics. Until now only a few wheel-rail contact models have been used for online simulation in multibody software (MBS). Many more models exist and their behaviour has been studied offline, but a comparative study of the mutual influence between the calculation of the creep forces and the simulated vehicle dynamics seems to be missing. Such a comparison would help researchers with the assessment of accuracy and calculation time. The contact methods investigated in this paper are FASTSIM, Linder, Kik-Piotrowski and Stripes. They are compared through a coupling between an MBS for the vehicle simulation and Matlab for the contact models. This way the influence of the creep force calculation on the vehicle simulation is investigated. More specifically this study focuses on the influence of the contact model on the simulation of the hunting motion and on the curving behaviour.

  • 16. Carlbom, P.
    et al.
    Berg, Mats
    KTH, Tidigare Institutioner                               , Farkost- och flygteknik.
    Passengers, seats and carbody in rail vehicle dynamics2002Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 37, s. 290-300Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reliable models of passengers, seats and carbody are essential in order predict ride comfort of rail vehicles. This paper extends previously presented models of passenger-carbody interaction to include vertical seating dynamics. The proposed basic model is based on experimental modal analysis of a rail vehicle with and without passengers. The nations of human-body normalized apparent mass and seat transmissibility are fundamental an the modelling. The possibility of using reduced and approximate gels is also discussed in the paper. The proposed models are easy to use and implemented in commercial rail vehicle software.

  • 17.
    Casanueva, Carlos
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Enblom, Roger
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. Bombardier Transportation, Swedem.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Comparison of wear prediction models for different contact conditions2016Inngår i: Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics (IAVSD 2015), Graz, Austria, 17-21 August 2015 / [ed] Martin Rosenberger, Manfred Plöchl, Klaus Six, and Johannes Edelmann, CRC Press, 2016, s. 871-878Konferansepaper (Fagfellevurdert)
    Abstract [en]

     Simulation of wheel and rail wear allows to predict long term profile evolution and thus, study the consequences of wheel damage in the dynamic behaviour of the vehicle, or study future maintenance requirements. Several models have been developed which try to solve the wear issue by relating the energy dissipated in the wheel-rail contact to the worn out material, from which two can be highlighted (Tg/A and Archard) which have significant differences on contact level. Even though, the prediction of long term wheel profile evolution has been validated with these two models, which means that for regular applications they seem to have an equivalent behaviour. In this work similarities and differences between the long term wear prediction methodologies are analysed, discussing their actual limitations. Then, these differences are exploited in specific operational cases to compare their wear prediction performance.

  • 18.
    Chaar, Nizar
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Dynamic wheel-rail force measurements and simulations of a high-speed train running on two tracks with different flexibility and irregularitiesArtikkel i tidsskrift (Annet vitenskapelig)
  • 19.
    Chaar, Nizar
    et al.
    KTH, Tidigare Institutioner, Farkostteknik.
    Berg, Mats
    KTH, Tidigare Institutioner, Farkostteknik.
    Experimental and numerical modal analyses of a loco wheelset2004Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 41, nr Suppl., s. 597-606Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wheelset structural flexibility is believed to have a major influence on the vehicle-track dynamics. Several studies have related the structural flexibility of the wheelset to fluctuations of wheel-rail forces, rail and wheel corrugation, etc. This paper reports part of an ongoing project that studies the effects of wheelset structural flexibility on the vehicle-track dynamics. The paper focuses on experimental and numerical modal analyses of a loco wheelset in the frequency range of 0-500 Hz. Major issues related to modal analyses and modelling of wheelset are presented along with respective results. The results from numerical modal analysis were in good agreement with those obtained from the experiment. In addition, the wheelset had fairly low eigenfrequencies. Reduced versions of the generated wheelset model will be used in coming work in on-track numerical simulations in order to determine the effects of wheelset structural flexibility on the vehicle-track dynamics. Results from these simulations will be validated against existing experimental on-track results.

  • 20.
    Chaar, Nizar
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Simulation of vehicle-track interaction with flexible wheelsets, moving track models and field tests2006Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 44, nr Suppl., s. 921-931Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Vehicle-track dynamic interaction emerged as a key multi-aspect subject following the development in high-speed and high axle-load trains. In this context. wheelset structural flexibility and track flexibility are the two main factors that contribute to high frequency content of the wheel-rail forces and influence the vehicle-track damage. Appropriate wheelset and track flexibility models are hence of great importance in pertinent numerical simulations. The present study comprises vehicle-track dynamic simulations considering wheelset structural flexibility and advanced moving track models. Simulated wheel-rail forces are then validated against measured data. The effects of the wheelset structural flexibility and track flexibility on the wheel-rail forces are investigated in the frequency range 0-150 Hz. The influence of track modelling and pertinent data on the simulation results is particularly assessed through a set of moving track models. Measured track data, i.e. irregularities, roughness and flexibility support the simulations. It is confirmed that track flexibility with appropriate modelling and data is important when examining the vehicle-track interaction. In the present case study, the influence of wheelset structural flexibility on the lateral wheel-rail forces is quite significant too.

  • 21.
    Chaar, Nizar
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Vehicle-track dynamic simulations of a locomotive considering wheelset structural flexibility and comparison with measurements2005Inngår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, ISSN 0954-4097, Vol. 219, nr 4, s. 225-238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wheelset structural flexibility, that is the elastic deformation of the wheelset as a structure, can significantly influence the vehicle-track dynamic interaction. In this paper on-track simulations considering flexible wheelsets, modelled through eigenmodes derived from a finite element model, are presented and compared with on-track measurements. The effects of the wheelset structural flexibility on track forces, in the frequency range 0-100 Hz, are investigated. Results from parametric studies are also presented. The present application is a Swedish Rc7 locomotive having rather slender wheelsets. It is shown that both lateral and vertical track forces are significantly influenced by the wheelset flexibility and that the agreement with measurements is fairly good. The wheelset flexibility increases the lateral track forces. The track representation in the present context is important and the used so-called moving track model needs improvements.

  • 22.
    Diedrichs, Ben
    et al.
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Berg, Mats
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Krajnovic, Sinisa
    Large eddy simulations of a typical European high-speed train inside tunnels2004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This article presents our results of external aerodynamics, obtained with Large Eddy Simulations(LES), about a typical European passenger-stock insidetunnels. The focal points are the aerodynamic forces andtheir typical frequencies applied to the tail. Two trainlengths and three tunnels are employed in the study tomodel the conditions of double and single-track bores.Owing to the relatively high numerical cost associated with LES for external train aerodynamics we could only afford sufficient spatial grid resolution on our shortest train. The flow simulations confirm the existence of coherent structures alongside the body that give rise to continuously propagating pressure disturbances. These disturbances with a relatively small amplitude and high spatial frequency cannot affect the ride comfort. Still,they are found to influence the flow separation about the tail, which is regarded as one of the candidate mechanisms to impair the ride comfort and running stability.

  • 23.
    Diedrichs, Ben
    et al.
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Berg, Mats
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Krajnovic, Sinisa
    Large eddy simulations of the flow around high-speed trains cruising inside tunnels2004Inngår i: ECCOMAS 2004 - European Congress on Computational Methods in Applied Sciences and Engineering / [ed] P. Neittaanmäki, T. Rossi, S. Korotov, E. Oñate, J. Périaux, and D. Knörzer, 2004, s. 1-21Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stability and ride comfort of high-speed rolling stock are, for reasons of external aerodynamics, dependent on the external design in conjunction with properties of the vehicle dynamics and the design of the infrastructure, herein referring to the confining tunnel walls. It is a fact that some Japanese high-speed trains are quite prone to tail vehicle vibrations only inside tunnels, while (to the authors' knowledge) other nation's comparable train systems are not. In this context the current work describes our results of external aerodynamics, calculated with large eddy simulations, about two simplified train models inside two double track tunnels with comparable blockage ratio. These models are based on the German Inter-City Express 2 and the Japanese Series 300 Shinkansen trains. The focal points of this study are the origin of unsteady aerodynamic tail forces, their spectral characteristics and the impact of spontaneously emerging coherent flow structures adjacent to the train's surfaces. Full scale tests of the above trains have shown that only the Shinkansen train is subjected to a reduced ride comfort inside tunnels, with a quite obvious lateral vibration at about 2 Hz at top speed (300 km/h). Our unsteady flow calculations have successfully predicted the more detrimental lateral aerodynamic forces. In addition, a spectral analysis of the unsteady side force resulted in a quite prominent frequency at the Strouhal number of 0.09 (based on the speed and height of the train), which correlates well with the Japanese full scale tests.

  • 24.
    Diedrichs, Ben
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Stichel, S.
    Krajnovic, S.
    Vehicle dynamics of a high-speed passenger car due to aerodynamics inside tunnels2007Inngår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 221, nr 4, s. 527-545Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High train speeds inside narrow double-track tunnels using light car bodies can reduce the ride comfort of trains as a consequence of the unsteadiness of the aerodynamics. This fact was substantiated in Japan with the introduction of the series 300 Shinkansen trains more than a decade ago, where the train speed is very high also in relatively narrow tunnels on the Sanyo line.

    The current work considers the resulting effects of vehicle dynamics and ride comfort with multi-body dynamics using a model of the end car of the German high-speed train ICE 2. The present efforts are different from traditional vehicle dynamic studies, where disturbances are introduced through the track only. Here disturbances are also applied to the car body, which conventional suspension systems are not designed to cope with.

    Vehicle dynamic implications of unsteady aerodynamic loads from a previous study are examined. These loads were obtained with large eddy simulations based on the geometry of the ICE 2 and Shinkansen 300 trains.

    A sensitivity study of some relevant vehicle parameters is carried out with frequency response analysis (FRA) and time domain simulations. A comparison of these two approaches shows that results which are obtained with the much swifter FRA technique are accurate also for sizable unsteady aerodynamic loads. FRA is, therefore, shown to be a useful tool to predict ride comfort in the current context.

    The car body mass is found to be a key parameter for car body vibrations, where loads are applied directly to the car body. For the current vehicle model, a mass reduction of the car body is predicted to be most momentous in the vicinity of 2 Hz.

  • 25.
    Diedrichs, Ben
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Krajnovic, Sinisia
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    On the aerodynamics of car body vibrations of high-speed trains crusing inside tunnels2008Inngår i: ENGINEERING APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS, ISSN 1994-2060, Vol. 2, nr 1, s. 51-75Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aerodynamically induced car body vibrations of high-speed trains inside tunnels have for approximately two decades been recognized as a problem in Japan, while other nations' high-speed rail services have not reported similar problems. In order to shed light on this contradiction the scope of the present paper is to primarily explore tail car vibrations of Deutsche Bahn AG's high-speed train ICE 2 and Japan Railways series 300 Shinkansen train. Despite similarities of these two trains the problems are reported only for the latter. Several large eddy simulations are carried out to predict the aerodynamics around simplified and smooth models of the above mentioned trains inside tunnels. The results focus on the ability to resolve PPD (propagating pressure disturbances) generated alongside the bodies, unsteady aerodynamic forces and their corresponding frequencies. Mesh refinement studies are undertaken for both train models, where mesh independence is quite a challenge for this type of application. Affordable meshes appropriate for LES could only be achieved for models confined to a typical car length. For smooth models and for a model with three generic inter-car gaps, the high spatial frequency of the resolved PPD does not make them sufficient to upset the ride quality of a car. A low frequency mode that strongly affects the forces of the tail of the Shinkansen models is described, which is caused by the confinement of the tunnel walls. A study of the implications of the lateral distance to the wall is further investigated. The findings reveal that the effects of the low frequency mode intensify with a narrow wall clearance, corresponding to the nominal lateral position of the train.

  • 26.
    Dirks, Babette
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Enblom, Roger
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. Bombardier Transportation, Sweden .
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Prediction of wheel profile wear and crack growth - comparisons with measurements2016Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 366, s. 84-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model which can predict the length of the surface crack and crack depth in rails was developed in a previous study by the authors B. Dirks, R. Enblom, A. Ekberg, M. Berg (2015) []. In the present study, verification of this crack prediction model in combination with a wear prediction model was done against wheel measurements. For a period of 15 months, the wheels of three units of a Stockholm commuter train were measured with respect to wear and crack development for verification of the wheel life prediction tool. Vehicle-track dynamics simulations were used to calculate the forces and contact positions for the wear and crack prediction models. It can be concluded that the wear prediction model gives reasonable results, especially considering the large scatter in the wheel profile measurements. Although the wheel life prediction tool could not be verified, since the crack prediction model had to be recalibrated for the current wheel application, the results appear promising.

  • 27.
    Dirks, Babette
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Enblom, Roger
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Prediction of wheel profile wear and crack growth: Comparisons with measurements2015Inngår i: CM 2015 - 10th International Conference on Contact Mechanics of Wheel / Rail Systems, 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A model which can predict the surface crack length and crack depth in rails was developed in a previous study by the authors1. In the present study, this crack prediction model in combination with a wear prediction model is verified against wheel measurements. For a period of 15 months, the wheels of three units of a Stockholm commuter train were measured with respect to wear and crack development. Vehicle-track dynamics simulations were used to calculate the forces and contact positions for the wear and crack prediction models. It can be concluded that the wear prediction model gives reasonable results, especially considering the large scatter in the wheel profile measurements. Although the crack prediction model had to be adjusted for the current wheel application, the results appear promising.

  • 28.
    Dirks, Babette
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Enblom, Roger
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. Bombardier Transportation, Sweden.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Prediction of wheel profile wear and crack growth: comparisons with measurementsManuskript (preprint) (Annet vitenskapelig)
  • 29.
    Dirks, Babette
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Enblom, Roger
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. Bombardier Transportation, Sweden.
    Ekberg, A.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    The development of a crack propagation model for railway wheels and rails2015Inngår i: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695, Vol. 38, nr 12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rolling contact fatigue (RCF) and wear of railway wheels and rails are the main phenomena that affect their maintenance costs. When crack propagation and wear rates can be predicted, maintenance planning can be optimised, and cost-effective measures can be developed. Several RCF models exist, but none which can be used in combination with vehicle dynamics simulations and can predict the actual crack depth. This study shows the development of a crack propagation model that can be applied for both railway wheels and rails. Two unknown material parameters in the model were calibrated against crack measurements in a curve on the Dutch railways over a period of 5years. Two different RCF models were used to calculate the stress magnitudes for the propagation model. The propagation model can be used in combination with vehicle-track dynamics simulations and shows promise in predicting the actual crack depth and/or surface length. Further research is needed to determine the model’s validity for other operational conditions.

  • 30.
    Enblom, Roger
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Emerging engineering models for wheel/rail wear simulation2005Inngår i: Proceedings of the 8th International Conference Railway Engineering, London, June 29-30, 2005, 2005Konferansepaper (Fagfellevurdert)
  • 31.
    Enblom, Roger
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Impact of non-elliptic contact modelling in wheel wear simulation2008Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 265, nr 9-10, s. 1532-1541Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Advances in simulation of railway wheel wear in the sense of material removal have drawn the attention to the importance of wheel–rail contact modelling. As a further step of enhancing the used simulation procedure in direction of increased generality and reduced need for application-dependent calibration, the focus of this investigation is the influence of non-elliptic contact models on the wheel wear rate and profile shape. To facilitate evaluation the semi-Hertzian contact procedure Stripes, developed by INRETS in France, has been implemented.

    To investigate the capabilities of Stripes to assess the contact area and pressure, shape comparisons have been made with other numerical methods for a set of wheel–rail contact situations. The referenced results are based on the linear elastic half-space assumption, elastic finite element analysis, and elastic–plastic finite element analysis. For reference also the elliptic contact area according to Hertz is shown as given by the contact data table of the multi-body simulation code.

    After exploring the properties of the Stripes procedure with respect to contact area estimation and pressure distribution, the focus is moved to the influence on wear rate, being the principal objective of this investigation. First the wear distribution over the contact patch is studied and compared to results using the elliptic model from the MBS code Gensys and the non-elliptic approach with Kalker's code Contact. Finally the evolution of the wheel profile is simulated for a few typical cases.

    This investigation of wear distributions over non-elliptic patches under different operating conditions indicates significant differences compared to both Contact and the applied Hertzian approach. The expansion from single contact occasions to complete simulations indicates comparable material removal rates but relocation towards the flange side. This tendency is apparent in all of the cases shown, however limited to initial wear in tangent run or reasonably mild curve negotiation.

  • 32.
    Enblom, Roger
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Proposed procedure and trial simulation of rail profile evolution due to uniform wear2008Inngår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 222, nr 1, s. 15-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A procedure for numerical simulation of rail wear and the corresponding profile evolution has been formulated. The wear is assumed to be uniform in the sense that the profiles remain constant along the track portion to be investigated. A simulation set is selected defining the vehicles running on the track, their operating conditions, and contact parameters. Several variations of input data may be included together with the corresponding occurrence probability.

    Simulation of multi-body dynamics is used to calculate contact forces and positions, and Archard's wear equation is applied for the calculation of wear depth. Wear coefficients as a function of contact pressure and relative sliding velocity are collected from different test results.

    Trial calculations of four non-lubricated and two lubricated curves with radii from 303 to 802 m show qualitatively reasonable results in terms of profile shape development and difference in wear mechanisms between gauge corner and rail head. The wear rates related to traffic tonnage are, however, overestimated and the lubrication efficiency underestimated.

    It is expected that model refinements in terms of environmental influence and contact stress calculation are useful to improve the quantitative results.

  • 33.
    Enblom, Roger
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Simulation of railway wheel profile development due to wear: influence of disc braking and contact environment2005Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 258, nr 7-8, s. 1055-1063Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper addresses issues related to braking and wheel-rail contact conditions in the context of wheel wear simulation. The KTH approach to the topic includes Archard's wear model with associated wear maps, vehicle dynamics simulation and railway network definition. In previous work at KTH certain variations in operating conditions have been accounted for through empirically estimated average scaling factors. The objective of the current research is to be able to include such variations in the set of simulations. In particular the influence of disc braking as well as varying friction and lubrication conditions are investigated. Both environmental factors like moist and contamination and deliberate lubrication need to be considered. As part of the associated contact analysis the influence of local elastic deformation on the sliding velocity has been separately investigated.

  • 34.
    Enblom, Roger
    et al.
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Berg, Mats
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Tentative Formulation of Simulation of Rail Profile Evolution due to Uniform WearArtikkel i tidsskrift (Annet vitenskapelig)
  • 35.
    Enblom, Roger
    et al.
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Berg, Mats
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Towards calibrated wheel wear simulation: a comparison between traditional approach and novel methods2004Inngår i: Proceedings of the 6th International Conference on Railway Bogies and Running Gears, Budapest, September 13-16, 2004., 2004Konferansepaper (Fagfellevurdert)
  • 36.
    Enblom, Roger
    et al.
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Berg, Mats
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    Wheel Wear Modelling Including Disc Braking and Contact Environment: Simulation of 18 Months of Commuter Service in Stockholm2004Inngår i: Proceedings of the 14th International Wheelset Congress, 2004Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    This paper addresses some aspects of modelling and validation of wheel wear simulation. In previous work at KTH the influences of braking and lubrication have been accounted for through empirically estimated average scaling factors. The current research shows how to include those effects in the set of simulations instead. Disc braking has been included in the simulation set and a wear map for moist contact conditions based on recent tribometer tests has been drafted and tested. Good agreement with measurements from theStockholmcommuter service is achieved. It is concluded that the model improvements accounted for are sufficient for adequate simulation of tread wear but that further development of the flange / gauge corner contact modelling is needed.

  • 37. Evans, J.
    et al.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Challenges in simulation of rail vehicle dynamics2009Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 47, nr 8, s. 1023-1048Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rail vehicle dynamic simulation has progressed a long way from its origins as a research tool. Modern multibody software packages are used as an essential part of the design process for new vehicles and for investigating service problems with existing vehicles. Increasingly, simulation is being used as part of the vehicle acceptance process in place of on-track testing. This state of the art paper for the 21st IAVSD Symposium in Stockholm in August 2009 surveys the current applications for rail vehicle dynamic modelling. The process of reducing a complex mechanical system to a mathematical representation is invariably subject to compromise and open to individual interpretation. The level of detail and choice of idealisation of suspension components will depend on the application, and in the real world it also depends on the availability of information about the system. This paper discusses appropriate modelling choices for different applications, and comments on best practice for the idealisation of suspension components, wheel/rail contact conditions and modelling inputs such as track geometry. The validation of simulation results is increasingly important, and this paper discusses recent trends in this area. Finally, the paper takes a brief look forward to future simulation issues.

  • 38.
    Forsberg, Tobias
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Andersson, Evert
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Condition Monitoring of Train Ride Stability2007Inngår i: Proceedings of the 7th International Conference on Railway Bogies and Running Gears, BOGIE'07, Budapest, September 3-6, 2007, 2007, s. 271-280Konferansepaper (Fagfellevurdert)
  • 39. Jendel, T.
    et al.
    Berg, Mats
    KTH, Tidigare Institutioner                               , Farkost- och flygteknik.
    Prediction of wheel profile wear - Methodology and verification2002Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 37, s. 502-513Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A wheel profile wear prediction toot is presented and verified by using a case study. A methodology is introduced that is based an a load collective concept, where representative vehicle-track simulations are chosen to take into account parameters that affect wheel wear. Key parts of the toot are load collective design, vehicle-track simulations, wheel-rail contact response calculations, wear calculations and wheel profile updating. Simulated and measured wheel profiles and corresponding scalar wear measures agree well.

  • 40.
    Karis, Tomas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Järnvägsteknik.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Analysing the correlation between vehicle responses and track irregularities using dynamic simulations and measurementsManuskript (preprint) (Annet vitenskapelig)
  • 41.
    Karis, Tomas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Analysing the correlation between vehicle responses and track irregularities using dynamic simulations and measurements2019Inngår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 42.
    Karis, Tomas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Li, M.
    Trafikverket, Borlange, Sweden..
    Thomas, D.
    SNC Lavalin, Bromma, Sweden..
    Dirks, B.
    Bombardier Transportat, Vasteras, Sweden..
    Correlation of track irregularities and vehicle responses based on measured data2018Inngår i: 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, s. 1285-1290Konferansepaper (Fagfellevurdert)
    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.

  • 43.
    Karis, Tomas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Li, Martin
    Trafikverket.
    Thomas, Dirk
    SNC-Lavalin.
    Dirks, Babette
    Bombardier Transportation.
    Correlation of track irregularities and vehicle responses based on measured data2018Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 56, nr 6, s. 967-981Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 44.
    Krishna, Visakh V
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Tolerable longitudinal forces for freight trains in tight S-curves using three-dimensional multi-body simulations2019Inngår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 45. Li, M. X. D.
    et al.
    Berggren, E. G.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Assessment of vertical track geometry quality based on simulations of dynamic track-vehicle interaction2009Inngår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 223, nr 2, s. 131-139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study assessing vertical track geometry quality based on simulations of dynamic track-vehicle interaction is presented in this article. The dynamic model is composed of track, vehicle, and wheel-rail contact with moving irregularities and is solved in the frequency domain by fast Fourier transform or in the time domain by constructing a filter function based on system identification. Frequency-dependent stiffness and loss factor of railpads are used in this study. Numerical simulations are carried out for a 120 km long track to demonstrate the potential benefits of enhancing track quality assessment by calculating wheel-rail forces.

  • 46. Li, M. X. D.
    et al.
    Berggren, E. G.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Persson, I.
    Assessing track geometry quality based on wavelength spectra and track-vehicle dynamic interaction2008Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 46, nr Suppl. S, s. 261-276Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a study of assessing track geometry quality (longitudinal level and alignment) by the use of dynamic track-vehicle simulations and wavelength spectra analysis. Two simulation models are developed: one is based on the software package GENSYS, which provides realistic simulations of the nonlinear dynamic behaviour of a vehicle running on real track. and (he other one is based on a newly developed linear track-vehicle model. which is Suitable for effectively calculating wheel-rail forces for very long track sections. The linear model. first proposed in 11,21 to assess vertical track geometry quality (longitudinal level), is extended in the present paper to simulate lateral track-vehicle dynamic interaction and, thus, to assess lateral track geometry quality (alignment) as well. Numerical results are presented to compare the simulation results with online measurement and to demonstrate the possibilities of enhancing track quality assessment and maintenance by simulations of track-vehicle interaction.

  • 47. Li, Martin
    et al.
    Persson, Ingemar
    Spännar, Jan
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    On the use of second-order derivatives of track irregularity for assessing vertical track geometry quality2012Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 50, nr SUPPL. 1, s. 389-401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper studies the use of second-order derivatives of track irregularities (longitudinal level, LL) for assessing vertical track geometry quality. Both a single-degree-of-freedom and a three-DOF vehicle-track model are investigated in order to explain theoretically why from the aspect of vehicle-track dynamic interaction it is relevant to consider not only the amplitudes of LL but also their second-order derivatives (LL2). Simulation results are then presented to demonstrate that dynamic vertical track forces are more correlated with the second-order derivatives (LL2) than to the amplitudes (LL) themselves. A comparison of the power spectral density (PSD) spectra for typical track reveals that it is more convenient to use the PSD spectra for the second-order derivatives than for the amplitudes, as the curves for the second-order derivatives are flat within the short wavelength range. Finally, the practical use of derivatives within the maintenance management system in order to achieve improved assessment of track geometry quality is also discussed.

  • 48. Lundén, Roger
    et al.
    Ekberg, Anders
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för teknikvetenskap (SCI), Centra, Järnvägsgruppen, JVG.
    Grassie, Stuart
    Special edition of "Wear" to contain CM2015 proceedings2016Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 366, s. 1-2Artikkel i tidsskrift (Fagfellevurdert)
  • 49.
    Mandal, Nirmal Kumar
    et al.
    Cent Queensland Univ, Ctr Railway Engn, Rockhampton, Qld 4702, Australia..
    Spiryagin, Maksym
    Cent Queensland Univ, Ctr Railway Engn, Rockhampton, Qld 4702, Australia..
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    On the railhead material damage of insulated rail joints: Is it by ratchetting or alternating plasticity?2019Inngår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 128, artikkel-id 105197Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 50.
    Marsilla, Maria
    et al.
    Stadler Rail Valencia.
    Berg, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Krishna, Visakh V
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Jobstfinke, Daniel
    Technische Universität Berlin (TUB).
    Melzi, Stefano
    Politecnico di Milano (POLIMI).
    Gisbert, Rafael
    Stadler Rail Valencia.
    D3.2 – Safety precautions in train configuration and brake application2018Rapport (Annet vitenskapelig)
    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).

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