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Proceedings of the Institution of Mechanical Engineers Part F: Journal of Rail and Rapid Transit

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ISSN (Print) 0954-4097 - ISSN (Online) 2041-3017
Published by Sage Publications

[700 journals]

Non-stationary random vibration of a coupled vehicle-slab track system using a parallel algorithm based on the pseudo excitation method
- Authors: Zhang, J; Zhao, Y, Zhang, Y.-h, Jin, X.-s, Zhong, W.-x, Williams, F. W, Kennedy, D.
  Pages: 203 - 216
  Abstract: A parallel algorithm based on the pseudo excitation method (PEM) is applied to investigate the non-stationary random response of a vertically coupled vehicle–slab track system subjected to random excitation induced by track irregularity. The vehicle is simplified as a multibody system with 10 degrees of freedom and the slab track is represented by a three layer Bernoulli–Euler beam model which includes the rail, slab and roadbed. Linear wheel–rail contact provides interaction between the vehicle and slab track models. The track irregularity is assumed to be a Gaussian random process with zero mean value and the non-stationary random response of the coupled vehicle–slab track system is solved using a combination of PEM and step-by-step integration. A parallel algorithm based on PEM is used to accelerate the computation and the effectiveness of the proposed method is verified by the Monte Carlo method. The basic random performance of the coupled vehicle–slab track system is analysed and the effects of the vehicle speed and slab track parameters on the random responses of the vehicle and slab track are investigated. The results indicate that the vehicle speed has a significant effect on the random response of the coupled vehicle–slab track system and that the rail pad parameters are the most important of the slab track parameters discussed.
  PubDate: 2013-04-09T08:33:57-07:00
  DOI: 10.1177/0954409712458403|hwp:master-id:sppif;0954409712458403
  Issue No: Vol. 227, No. 3 (2013)
Representation of mechanic hysteresis in a railway track using the Preisach model
- Authors: Koc, W; Wilk, A, Chrostowski, P, Grulkowski, S.
  Pages: 217 - 228
  Abstract: This paper presents an implementation of the classic scalar Preisach model to describe the hysteresis phenomenon created in a railway track subjected to lateral (in the horizontal plane) displacements. The principles of the Preisach theory and the scalar mathematical model of the mechanical hysteresis that is based on statistically distributed modified hysteresis operators are briefly presented. This article presents the characteristic states of the track displacements under lateral forces and their interpretation using the Preisach phase diagram. Formulas are presented that allow the calculation of the trajectory of the track displacements using the Preisach distribution function (PDF) and the Everett function (EF). Identification methods for the PDF and EF presented in the literature are discussed. A mathematical formula for the calculation of the EF on the basis of the major hysteresis loop is presented. The implemented hysteresis model is validated by comparing simulation results with experimental data. A good level of agreement between the two sets of results is observed which confirms the validity of the proposed model. The shape of the hysteresis loop created in the rail track depends on the stress state in the rails. It is suggested that this observation could be used to create an effective method to assess axial forces in continuous welded rail track.
  PubDate: 2013-04-09T08:33:57-07:00
  DOI: 10.1177/0954409712460008|hwp:master-id:sppif;0954409712460008
  Issue No: Vol. 227, No. 3 (2013)
The effect of enhanced curving forces on the behaviour of canted ballasted track
- Authors: Priest, J. A; Powrie, W, Le Pen, L, Mak, P, Burstow, M. C.
  Pages: 229 - 244
  Abstract: The performance of railway ballast depends not only on the characteristics of the ballast itself but also the magnitude, frequency and number of axle loads imposed by the trains running on the track it supports. Recent trends towards more frequent and faster trains have highlighted some potential limitations of ballasted railway track. In particular, the introduction of tilting trains on the UK West Coast Main Line, which allowed train operating speeds to be increased over much of the route, has coincided with the sporadic occurrence of localized areas of ballast migration. This phenomenon involves ballast particles moving from the high side of a canted section of track to the low side, exposing the sleeper ends on the high (outer) side of the curve, reducing the lateral resistance of the track and therefore increasing maintenance requirements. This paper reports the results of an investigation carried out to try to identify the underlying mechanism responsible for this behaviour. Measurements of sleeper end displacements under the passage of trains were made at two locations which had experienced ballast migration. Analysis of the measured data together with numerical modelling of the forces imposed on the track structure suggest that the increased speed and typical axle loads of the tilting trains result in larger lateral forces and larger rotation of the sleeper (in the vertical plane) than for a train consisting of a locomotive plus trailing vehicle, as was previously used on the route. It is hypothesized that this leads in turn to a slow but progressive movement of the ballast down the slope of the canted track. However, given the highly localized nature of the ballast migration sites, other factors such as an irregular sub-base stiffness and ballast depth may also contribute to the phenomenon and further work is required to determine the combinations of circumstances that may trigger this effect.
  PubDate: 2013-04-09T08:33:57-07:00
  DOI: 10.1177/0954409712458623|hwp:master-id:sppif;0954409712458623
  Issue No: Vol. 227, No. 3 (2013)
Wayside gauge face lubrication: How much do we really understand?
- Authors: Eadie, D. T; Oldknow, K, Santoro, M, Kwan, G, Yu, M, Lu, X.
  Pages: 245 - 253
  Abstract: Wayside gauge face lubrication is widely used to minimize rail wear. Scientific understanding of this process is limited; however, there have been significant recent improvements in application equipment. In this paper the process is analyzed in terms of a number of interacting sub-processes, and the factors thought to be important for lubricant and application equipment are reviewed. Wheel/rail contact conditions (pressure and temperature) are also identified as significant variables. Grease stability and retentivity are significant factors that affect lubricant performance; however, significant knowledge gaps exist about the factors that influence grease pick up and carry down especially at the extremes of operating temperatures. Laboratory (two-roller rig measurement of retentivity) and field evaluation (rail friction measurements of carry down) gave the same relative ranking for the tested grease samples. Areas for future research in the area are identified.
  PubDate: 2013-04-09T08:33:57-07:00
  DOI: 10.1177/0954409712459306|hwp:master-id:sppif;0954409712459306
  Issue No: Vol. 227, No. 3 (2013)
Measurements and simulation of the dynamic responses of a bridge-embankment transition zone below a heavy haul railway line
- Authors: Shi, J; Burrow, M. P. N, Chan, A. H, Wang, Y. J.
  Pages: 254 - 268
  Abstract: Chinese Railways is seeking to increase the capacity of many of its heavy haul railway lines by increasing their utilization and at the same time increasing axle loads from 250 to 300 kN. These projected increases in railway traffic may result in accelerated deterioration of the railway network. A vulnerable part of the network, are bridge–embankment transition zones which frequently experience high degradation rates. To investigate the possible implications of the forecasted increases in railway traffic on these structure, a study was carried out which consisted of instrumenting a transition zone to measure accelerations under existing loads and building a three-dimensional finite element dynamic model of the bridge–embankment transition to predict the effects of the anticipated future traffic. The results of the study indicated that commonly used measures of stability, safety and substructure damage would remain within specified limits, despite the projected increases in axle load. However, excessive wear of the wheel and or rail may occur.
  PubDate: 2013-04-09T08:33:57-07:00
  DOI: 10.1177/0954409712460979|hwp:master-id:sppif;0954409712460979
  Issue No: Vol. 227, No. 3 (2013)
Maximising heat dissipation from ventilated wheel-hub-mounted railway brake discs
- Authors: Galindo-Lopez, C. H; Tirovic, M.
  Pages: 269 - 285
  Abstract: Improvement of convective heat dissipation from wheel-mounted discs presents a unique challenge due to the existence of a secondary air flow (in the circumferential direction), between the vanes and wheel web. Although this flow reduces pumping efficiency (air mass flow), it promotes air mixing between different channels and increases turbulence. Beginning with the existing design, a procedure was developed to maximise convective heat dissipation based on specific post-processing procedures and monitored parameters. These included the secondary flow (behind the vanes), air speed in the channels at specific planes and points, global air flow pattern and the distribution of the convective heat transfer coefficient. By analysing these plots and graphs it was possible to identify areas where flow and heat transfer characteristics could be improved. Ultimately, the specific power dissipation (the product of the average convective heat transfer coefficient and the disc wetted area), provided a single quantitative measure of disc design effectiveness in convective cooling. The newly developed design showed an increase in convective heat dissipation of over 10% when compared with the existing disc.
  PubDate: 2013-04-09T08:33:57-07:00
  DOI: 10.1177/0954409712462337|hwp:master-id:sppif;0954409712462337
  Issue No: Vol. 227, No. 3 (2013)
Impact of superelevation deficiencies on the loading pattern of railway sleepers
- Authors: Sadeghi, J; Shoja, H.
  Pages: 286 - 295
  Abstract: Although the loads transferred from a rail to a sleeper and from the sleeper to the ballast have been thoroughly investigated in the literature, little attention has been paid to the influence of superelevation deficiency (SED) on the loading pattern of the sleeper. A thorough field investigation into the effects of SED on the mechanical behavior of railway sleepers was carried out in this research. For this purpose, several load cells were installed above and beneath a sleeper in order to record the loads transferred from the rail to the sleeper and from the sleeper to the ballast, for a railway track with various SED levels. The results obtained were analyzed and a mathematical model for the loading pattern on the sleeper was developed. This model is a function of axle load, train speed, sleeper length and SED. Application of the proposed model in the design of sleepers indicates that SED can have a considerable impact on the sleeper design parameters. Consequently, the sleeper design method can be improved by adding correction factors to the conventional formulation of sleeper bending moments.
  PubDate: 2013-04-09T08:33:57-07:00
  DOI: 10.1177/0954409712460978|hwp:master-id:sppif;0954409712460978
  Issue No: Vol. 227, No. 3 (2013)
Feasibility of discontinuous electrification on the Great Western Main Line determined by train simulation
- Authors: Hoffrichter, A; Silmon, J, Schmid, F, Hillmansen, S, Roberts, C.
  Pages: 296 - 306
  Abstract: The UK has a number of main line railway routes that are not yet electrified. Some of these routes are under active consideration for electrification and the UK Government has recently announced the electrification of the Great Western Main Line (GWML). Railway electrification requires a large capital investment in infrastructure. Areas with limited clearance, such as tunnels and sections through overbridges, are particularly expensive to electrify. In this paper, train performance on the GWML, from London Paddington to Cardiff and vice versa, is modelled for three cases: no electrification; full electrification; and electrification that does not include tunnels, most notably the Severn Tunnel. The modelled trains were: the High Speed Train hauled by pairs of Class 43 diesel-electric locomotives; the nine-car Class 390; and Intercity Express Programme (IEP) trains formed as straight electric or bi-mode multiple units. Bi-mode trains combine electric and diesel traction in the same train. The considered IEP trains included both five-car and eight-car bi-mode options. Journey time, energy consumption and CO2 emissions were determined in each case. Electrification of the route will result in a reduction in energy consumption, carbon emissions and journey time, with the longest trains offering the greatest benefit. Under normal conditions, all modelled trains were able to complete the journey under discontinuous electrification. However, a small reduction in entry speed into the Severn Tunnel resulted in stalling of the exclusively electric trains. Bi-mode rail vehicles completed the journey in all cases and, as to be expected, also when tunnel entry speed is reduced; journey time, energy consumption and carbon emissions are not majorly impacted compared to exclusively electric operation.
  PubDate: 2013-04-09T08:33:57-07:00
  DOI: 10.1177/0954409712461341|hwp:master-id:sppif;0954409712461341
  Issue No: Vol. 227, No. 3 (2013)