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  • 1.
    Abbasi, S.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Particle emissions from rail vehicles: A review2012In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 98Article in journal (Refereed)
    Abstract [en]

    Emission of airborne particles is a side effect from rail transport. This paper reviews recent research on particle emissions from rail vehicles. Both exhaust and non-exhaust particle emissions are characterized by size, morphology, composition, and size distribution. Current legislation, knowledge of adverse health effects, and available and proposed solutions for emission reductions are also treated. There has been much focus on exhaust emissions, but only a few limited studies have investigated non-exhaust particle emissions, which contain a significant amount of metallic materials. A new method for measuring the airborne wear particle emission rate (AWPER) is proposed as a first step to guide new legislations and to focus further research on non-exhaust airborne emission, i.e., research on the generation mechanisms for particle emissions and their adverse health effects. 

  • 2.
    Andersson, E.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Orvnäs, Anneli
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Persson, R.
    Passenger Trains Division, Bombardier Transportation, Västerås, Sweden.
    How to find a compromise between track friendliness and the ability to run at high speed2012In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 98Article in journal (Refereed)
    Abstract [en]

    When designing and optimizing a rail vehicle there is a contradiction between, on the one hand, stability on straight track at high speed and, on the other hand, reasonable wheel and rail wear in small- and medium-radius curves. This paper describes the process of developing and optimizing a track-friendly bogie. A simulation model has been used to investigate dynamic stability on straight track at high speeds along with the wheel and rail wear in sharper curves. The result is a bogie with relatively soft wheelset guidance allowing passive radial self-steering, which in combination with appropriate yaw damping ensures stability on straight track at higher speeds. This bogie has been tested according to EN 14363 at speeds up to about 300 km/h and in curves with radii ranging from 250 m and up. 

  • 3. Arvidsson, T.
    et al.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Modelling alternatives in the dynamic interaction of freight trains and bridges2014In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 104Article in journal (Refereed)
    Abstract [en]

    This paper focuses on studying the dynamic response of bridges under passing freight trains. To increase transport efficiency, infrastructure mangers are asked to allow for higher freight train speeds and higher axle loads. However, little work has been done on the influence of increased freight train speeds on bridges. In this paper a two-level factorial experiment was used to identify the most important factors in train-bridge interaction systems comprising the Swedish Steel Arrow freight train passing over simply supported beam bridges. Thereby, the effect of a simple 2D multibody model as opposed to moving forces was set in relation to variations in other key system parameters. Preceding the factorial experiment, four train models were compared to determine a relevant vehicle idealisation. Through the factorial design, effects of single parameters, as well as joint effects from simultaneous changes in several parameters, were evaluated. The type of load model was found to have a large effect, reducing the bridge deck response at resonance considerably for the four studied bridges of span 6, 12, 24 and 36 m. For the relatively light 24 and 36 m span bridges, clear resonance peaks from heavy freight train passages in the speed interval 50-150 km/h were much reduced.

  • 4. Bornet, Lucie
    et al.
    Andersson, A.
    Zwolski, J.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Influence of the ballasted track on the dynamic properties of a truss railway bridge2014In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 106Article in journal (Refereed)
    Abstract [en]

    This paper presents numerical and experimental analyses of a steel truss railway bridge. The main interest of this work is that dynamic experiments have been performed before and after the ballasted track was placed on the bridge. Consequently, it has been possible to quantify the effect of the ballast and the rails on the dynamic properties of the bridge. For that, two finite element models, with and without the ballasted track, have been implemented and calibrated using the experimental results. It appears that the ballast gives an additional stiffness of about 25-30% for the lowest three eigenmodes. This additional stiffness can be only partly explained by the stiffness of the ballast. In fact, it seems that this additional stiffness also results from a change of the support conditions.

  • 5.
    Casanueva, Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Krishna, Visakh V.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Jönsson, R.
    NTnet AB, Malmö, Sweden .
    Nelldal, Bo Lennart
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Payload optimization of articulated wagons considering train length and vehicle dynamic behaviour2016In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 110Article in journal (Refereed)
    Abstract [en]

    The Capacity4Rail EU project aims are improving the competitiveness and reliability of rail freight in order to make it more attractive for modern, more sophisticated market requirements. The work described in this paper, focuses on novel vehicle designs that can account for a higher payload per meter, both from the payload optimization and the vehicle dynamic response point of view. We analyze an articulated spine wagon composed of five car bodies and six bogies, of which four of them are shared between two car bodies. In the work package, there has been an effort to look into the implications of these very long wagons in all aspects of freight operation, and this paper focuses on two of these aspects: the gain in payload by using different configurations, and the analysis of the dynamic response of the running gear. The conclusion is that, from vehicle performance point of view, it is worth exploring the possibility of increasing payload by slightly reducing the dynamic behavior of the system, as the twelve-axle vehicle is much more flexible when it comes to modern multimodal transportation. © Civil-Comp Press, 2016.

  • 6.
    Cha, Y.
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM).
    Gustafsson, M.
    Johansson, C.
    On particulate emissions from individual trains in tunnel environments2016In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 110Article in journal (Refereed)
    Abstract [en]

    In order to detect the concentrations and size distributions of airborne particles that were generated by individual moving trains on an underground railway platform, a series of real-time measurements were undertaken. The measurement range covered the ultrafine (less than 100 nm) and partly the fine (100 nm to 2.5 μm), but not the coarse fraction (2.5 to 10 μm). The results show that the individual trains with stop and start at the platform elevate substantially the particulate number concentrations with a diameter size greater than 100 nm. Two size modes of the particulate number concentrations are obtained. One mode peaks around 170 nm when a train stopped/started, while the other is around 30 nm when no train operated in the station. By using principal component analysis, four components are extracted from the thirty two-analyzed particulate sizes, indicating four different contributors in those detected particles. It is revealed from this study that the particulate matter released by individual moving trains (mainly through mechanical wear and turbulent resuspension) is a key contributing source of the fine particles on underground railway platforms, which can be separated from the background by their different size distributions. © Civil-Comp Press, 2016.

  • 7.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Instabilities in pressurized membranes2014In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 106Article in journal (Refereed)
    Abstract [en]

    This paper discusses instabilities occuring in thin pressurized membranes, important in biological as well as in engineering contexts. The membranes are represented by only their in-plane stress components, for which an incompressible isotropic hyper-elastic behavior can be assumed. The inherently non-linear response to pressurization can give instabilities in the forms of limit points with respect to a loading parameter, but also bifurcations and wrinkling. The hyper-elastic material model itself can also, under some circumstances, lead to a bifurcation situation. The instability situations can be included as constraints in a structural optimization. The paper discusses the formulation, the solution methods and some relevant instability situations. A numerical example considering the internal pressurization of a cylindrical pre-stressed membrane illustrates some aspects of instability.

  • 8. Höjer, M.
    et al.
    Bergseth, Ellen
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Nilsson, R.
    Lyu, Yezhe
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A noise related track maintenance tool for severe wear detection of wheel-rail contact2016In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 110Article in journal (Refereed)
    Abstract [en]

    An on-board measurement system has been developed that in real time identifies the probability for occurrence and also the exact location of severe wear in the wheelrail contact. Noise generated by the wheel-rail contact is a troublesome side effect both when railway vehicles negotiate curves and run on straight tracks. The concept behind this project is to use this noise as an indicator of the transition from the mild wear regime to the severe/catastrophic wear regime that implies high maintenance cost. At first tribometers were used in a laboratory study to investigate the relationships between wear and the emitted noise. Wear transitions from mild to severe wear were always accompanied by an increase in sound pressure of about 10 dB. The transitions also changed the sound pressure amplitude distribution from a narrow banded to a broader banded distribution. Secondly a full scale test in a small radius curve in a depot was carried out using a metro train, type C20. In agreement with the laboratory tests, the same kind of transfer from mild to severe wear was identified on the full scale tests in the depot. In addition, the sound pressure changed significantly, both in amplitude and in distribution, when transferring from mild to severe wear. By comparing the noise from the inner wheel-rail contact to noise from the outer wheel-rail contact a wear detection parameter for the outer wheel-rail contact is suggested. The third part of this project involves validation of the maintenance tool by operating the instrumented train in normal metro traffic, while at the same time collecting wear particles and making replicate casts of the rail at critical locations in the metro. Further comparison with weather data and a maintenance log has also been performed. © Civil-Comp Press, 2016.

  • 9.
    Johansson, C.
    et al.
    KTH. ELU Konsult AB, Stockholm, Sweden.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB, Stockholm, Sweden.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Preliminary dynamic assessment of railway bridges subject to higher speeds2012In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 98Article in journal (Refereed)
    Abstract [en]

    Swedish authorities have begun investigating the consequence of upgrading three of their major railway lines from 200 km/h to 250 km/h. The total track length is more than 1200 km and covers over 1000 bridges. Obviously, it is only possible to perform finite element analysis for a limited number of bridges for which the dynamic effects are considered to be a problem. Thus, as a consequence of the large number of bridges, a more efficient assessment approach has to be developed. The project initiated exemplifies the way in which a simple model may be used to help select a suitable bridge type or to identify existing bridges with dynamical problem so that they can be further assessed. This paper presents design curves to calculate the maximum acceleration in multi-span bridges. 

  • 10.
    Liu, Hailong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Jonsson, Lage Tord Ingemar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. FOI, Swedish Defence Research Agency, Division of CBRN Defence and Security, Umeå, Sweden..
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A pin-on-disc study of airborne wear particles from dry sliding wheel-rail contacts2016In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 110Article in journal (Refereed)
    Abstract [en]

    Pin-on-disc laboratory tests were carried out to identify the generation of airborne wear particles in wheel-rail contacts under different sliding velocities. The results show that the sliding velocity significantly influences both the number and size distribution of airborne wear particles. A comparison of the contact temperature was obtained during tests. For tests with high sliding velocities (1.2 and 3.4 m/s), the particle number concentration level was related to the elevated contact temperature in selected time intervals. Moreover, morphological and elemental analyses of collected particles and pin worn surfaces were studied by using a scanning electron microscope and field emission-scanning electron microscope. The data suggests that the oxide layers were detected within the pin's worn surfaces and an abundant presence of iron-oxide containing particles was observed. Therefore, it can be concluded that abundant fine and ultrafine airborne particles are more likely to be produced from an oxidative wear process in a wheel-rail contact under high sliding velocities.

  • 11.
    Lyu, Yezhe
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Bergseth, Ellen
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    The effect of Subzero temperature and snow on the tribology of wheel-rail contact2016In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 110Article in journal (Refereed)
    Abstract [en]

    The wheel-rail system operates in an open environment where the weather condition varies constantly. In this laboratory study, an investigation using a pin-on-disc tribometer placed in a temperature-controlled room was conducted to examine the effect of subzero temperature and snow on friction and wear at the wheel-rail contact. In temperature range from 3 to-15 °C (without snow) friction and wear were dominated by low temperature brittleness, which led to an increase in friction and wear. When temperature decreased down to-25 °C, an ice layer condensed on the pin and disc surfaces, which then melted during sliding and acted as a lubricant, leading to the sharp decrease of friction and wear. When snow crystals were added into the contact they melted into water droplets during sliding because of pressure melting and reduced the friction and wear following the boundary lubrication mechanism. With increasing temperature from-25 to 3 °C, friction performed monotonously decreasing because of the increasing thickness of the water layer. A large area of oxide flakes generated on the worn surfaces also significantly protected the contacting wheels and rails from severe wear. © Civil-Comp Press, 2016.

  • 12.
    Muld, Toma. W.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Henningson, D. S.
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Mode decomposition of flow structures in the wake of two high-speed trains2012In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 98Article in journal (Refereed)
    Abstract [en]

    Two different train geometries, the Aerodynamic Train Model (ATM) and the CRH1, are studied in order to compare the flow structures in the wake. The flow is simulated with Detached Eddy-Simulation and then decomposed into modes with Proper Orthogonal Decomposition. This study has found that the flow structures are indeed different for the two train models although the tails are rather similar. For the CRH1 the dominant flow structures twist one of the counter-rotating vortices and leaves the other straight. The convergence of the modes are investigated and it is shown that approximately the same number of snapshots are needed for both trains. 

  • 13. White, B. T.
    et al.
    Lewis, R.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Lyu, Yezhe
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    The contribution of iron oxides to the wet-rail phenomenon2016In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 110Article in journal (Refereed)
    Abstract [en]

    This paper reviews the current literature regarding iron oxide formation in the wheel-rail contact in order to assess the possible role of iron oxides in the "Wet-Rail" phenomenon, which causes low adhesion between the wheel and the rail. The paper discusses the structure and formation of oxides from a chemical perspective before analysing the direct tribological effects and outlining the techniques that have been used to study the oxide layers. This paper also suggests how knowledge of the subject could be expanded and how further understanding of the "Wet-Rail" phenomenon could lead to better mitigation methods, resulting in both economic and safety benefits.

  • 14.
    Zhu, Yi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Olofsson, Ulf
    KTH, Superseded Departments (pre-2005), Machine Design.
    Nilsson, R.
    Stockholm Public Transport AB, Stockholm, Sweden.
    A field test study of leaf contamination on railhead surfaces2012In: Civil-Comp Proceedings, ISSN 1759-3433, Vol. 98Article in journal (Refereed)
    Abstract [en]

    Leaves on train tracks cause low adhesion between wheels and rails, especially in the autumn. A Stockholm local traffic track with a long history of adhesion problems was subject to field tests of railhead contamination. Over a year, on five occasions under different conditions, the friction coefficient was measured using a hand-push tribometer and rail samples were taken. ESCA and GD-OES analyses were conducted to determine the composition of the top layer of rail contaminants. The blackish layer contains much higher contents of calcium, carbon, and nitrogen than other samples indicating a chemical reaction occurring from the surface to a depth of several microns. The thickness of the friction-reducing oxide layer predicts the friction coefficient and leaf contamination extent. 

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