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Proceedings of the Institution of Mechanical Engineers Part F: Journal of Rail and Rapid Transit [6 followers] Follow

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0954-4097 - ISSN (Online) 2041-3017
Published by Sage Publications

[718 journals] [SJR: 0.449] [H-I: 21]

Simulation study of thermally initiated rail defects
- Authors: Scott, D; Fletcher, D, Cardwell, B.
  Pages: 113 - 127
  Abstract: Ultrasonically detected ‘squat-type’ rail defects are becoming increasingly common on railways throughout the world. On the London Underground (LU) these defects are found on three lines. Focussing on the difference between these lines and others on the LU network has identified vehicles with modern AC traction characteristics as a common theme found only on problem lines. Metallurgical analysis of the defects found that the mechanisms for generation and growth are not consistent with conventional rolling contact fatigue, with evidence of significant thermal input. The defects are only found on open sections. The areas most susceptible to the defects are those where low-speed running is more common. A mathematical model of the traction package has been used to examine the forces and thermal input generated at the wheel–rail interface with modern wheel-spin control systems under wheel slip and adhesion recovery conditions. The outputs have been analysed to assess whether sufficient forces and temperatures are generated to explain the observed rail damage. The results suggest that under certain circumstances wheel-spin recovery generates sufficient rail surface energy for martensitic transformation. Additional modelling suggests that thermal input from wheel-spin aids crack propagation and that regions of slightly degraded (wet as opposed to leaf or oil contaminated) rail adhesion are sufficient to initiate these flaws.
  PubDate: 2014-01-12T22:39:49-08:00
  DOI: 10.1177/0954409712465697|hwp:master-id:sppif;0954409712465697
  Issue No: Vol. 228, No. 2 (2014)
Comparison of dynamic effects of high-speed traffic load on ballasted track using a simplified two-dimensional and full three-dimensional model
- Authors: Nguyen, K; Goicolea, J, Galbadon, F.
  Pages: 128 - 142
  Abstract: The vertical dynamic actions transmitted by railway vehicles to the ballasted track infrastructure are evaluated taking into account models with different degrees of detail. In particular, this matter has been studied from a two-dimensional finite-element model to a fully coupled three-dimensional multibody finite-element model. The vehicle and track are coupled via a nonlinear Hertz contact mechanism. The method of Lagrange multipliers is used for the contact constraint enforcement between the wheel and rail. Distributed elevation irregularities are generated based on power spectral density distributions, which are taken into account for the interaction. Due to the contact nonlinearities, the numerical simulations are performed in the time domain, using a direct integration method for the transient problem. The results obtained include contact forces, forces transmitted to the infrastructure (sleeper) by railpads, and envelopes of relevant results for several track irregularities and speed ranges. The main contribution of this work is to identify and discuss coincidences and differences between discrete two-dimensional models and continuum three-dimensional models, as well to assess the validity of evaluating the dynamic loading on the track with simplified two-dimensional models.
  PubDate: 2014-01-12T22:39:49-08:00
  DOI: 10.1177/0954409712465710|hwp:master-id:sppif;0954409712465710
  Issue No: Vol. 228, No. 2 (2014)
Substitution of corrugated sheets in a railway vehicle's body structure by a multiple-requirement based selection process
- Authors: Wennberg, D; Stichel, S, Wennhage, P.
  Pages: 143 - 157
  Abstract: To simplify construction, reduce weight and improve mechanical properties, a sandwich panel substitution process is performed on corrugated sheets in the floor and roof of a rail vehicle car body. A requirement based selection is used to design the sandwich panels with the corrugated sheet mechanical characteristics as boundaries. Car body stiffness is evaluated by modal analysis. The derived panels reduce the mass of the car body by 600–700 kg. Results show the varying importance of the longitudinal, transverse and shear properties of the floor and roof panels, as well as how efficient the corrugated sheets actually are.
  PubDate: 2014-01-12T22:39:49-08:00
  DOI: 10.1177/0954409712467139|hwp:master-id:sppif;0954409712467139
  Issue No: Vol. 228, No. 2 (2014)
The application of an enhanced Brute Force algorithm to minimise energy costs and train delays for differing railway train control systems
- Authors: Zhao, N; Roberts, C, Hillmansen, S.
  Pages: 158 - 168
  Abstract: This paper demonstrates an enhanced Brute Force algorithm application for optimising the driving speed curve by trading off reductions in energy usage against increases in delay penalty. A simulator is used to compare the train operation performance with different train control system configurations when implemented on a section of high-speed line operating with two trains, including differences in journey time and train energy consumption. Results are presented using six different train control system configurations combined with three different operating priorities. Analysis of the results shows that the operation performance can be improved by eliminating the interactions between trains using advanced control systems or optimal operating priorities. The algorithm is shown to achieve the objectives efficiently and accurately. Control system configurations with intermediate levels of complexity (e.g. European Train Control System Levels 2 and 1 with in-fill) when coupled with the optimisation process have been shown to have similar performance to the more advanced control system.
  PubDate: 2014-01-12T22:39:49-08:00
  DOI: 10.1177/0954409712468231|hwp:master-id:sppif;0954409712468231
  Issue No: Vol. 228, No. 2 (2014)
Simple flexible wheelset model for low-frequency instability simulations
- Authors: Casanueva, C; Alonso, A, Eziolaza, I, Gimenez, J. G.
  Pages: 169 - 181
  Abstract: As a general rule, the multi-body simulation models used by railway vehicle designers consider the wheelsets to be fully rigid, thus leading to possible errors when calculating the critical speed of the vehicle under study. This article suggests a wheelset model that takes into account wheelset flexibility for the study of dynamic stability. The model is simple to implement, easily parameterised, and can be applied to both conventional and variable gauge wheelsets. The parameters corresponding to wheelset flexibility that most influence the critical speed of high-speed and variable gauge vehicles are also analysed.
  PubDate: 2014-01-12T22:39:49-08:00
  DOI: 10.1177/0954409712468253|hwp:master-id:sppif;0954409712468253
  Issue No: Vol. 228, No. 2 (2014)
An investigation into the use of asphalt layers to control stress and strain levels in railway track foundations
- Authors: Esmaeili, M; Amiri, S, Jadidi, K.
  Pages: 182 - 193
  Abstract: A hot mixed asphalt layer can be inserted between the ballast and subgrade layers in the foundations of rail tracks to improve the stress and strain distributions in these layers and also reduce track vibrations and level of damage in the track’s superstructure. These phenomena depend on various parameters such as the manner of operation of the railway and the mechanical characteristics of the foundations. This study is devoted to the derivation of analytical equations that describe the tensile strain on the asphalt layer and compression stress in the subgrade layer in terms of these parameters. A series of numerical analyses have been performed using the KENTRACK simulation code in which the railway axle load, asphalt thickness, ballast modulus and California bearing ratio of the subgrade were varied. The obtained values of the maximum tensile strain in the asphalt and compression stress on the subgrade were analysed using a least squares method in order to extract correlation equations that consider the maximum tensile strain in the asphalt layer and compression stress on the subgrade layer in terms of the varied parameters. A comparison of the obtained simulation results with measured data reported in the literature shows a good agreement between the results.
  PubDate: 2014-01-12T22:39:49-08:00
  DOI: 10.1177/0954409712468850|hwp:master-id:sppif;0954409712468850
  Issue No: Vol. 228, No. 2 (2014)
Particle image velocimetry of the underfloor flow for generic high-speed train models in a water towing tank
- Authors: Jonsson, M; Wagner, C, Loose, S.
  Pages: 194 - 209
  Abstract: The underfloor flow field of three different 1:50 generic high-speed train models hauled through a water towing tank at a speed of 4 m/s (Reynolds number = 0.24 x 106) over smooth ground, rough ground, and ground with sleepers is measured by means of two-component particle image velocimetry. The reference train model, consisting of four cars, features inter-car gaps and two bogies per car. These features are removed and all gaps are closed to create the smooth train configuration whereas the rough train configuration has all the gaps but no bogies. The lowest underfloor flow velocities and velocity gradients at the ground are observed for the smooth train model on the ground with sleepers. Furthermore, the measurements reveal that any additional irregularity of the underbody leads to regions characterised by flow acceleration in the otherwise Couette-like flow and this increases the possibility of ballast flight. Therefore, it is concluded that a smooth underbody can lower the risk of ballast flight. The results obtained for the reference train model are compared with those of a full-scale measurement. It is shown that the results of the water towing tank experiments with the scaled train model reflect the main characteristics of the underfloor flow of the full-scale measurements.
  PubDate: 2014-01-12T22:39:49-08:00
  DOI: 10.1177/0954409712470607|hwp:master-id:sppif;0954409712470607
  Issue No: Vol. 228, No. 2 (2014)
Tread braking of railway wheels - temperatures generated by a metro train
- Authors: Teimourimanesh, S; Vernersson, T, Lunden, R, Blennow, F, Meinel, M.
  Pages: 210 - 221
  Abstract: Tread braking of railway wheels results in the kinetic energy of the train being dissipated into the wheel and blocks in the form of heat. This heat is further conducted into adjacent structures, notably the cold rail, and also transferred into the surroundings by convection and radiation. Heat partitioning between wheel and block is, for short time periods, controlled by local thermal interactions at the contact point and by the conductive properties of the bodies. However, for a metro train that performs longer periods of intermittent braking (or for drag braking) convective and radiation cooling properties of the components come into play. In the present study, results from brake rig tests and from in-field testing of a metro train are presented and used to calibrate a simulation model. It is found that the cooling level of the wheels of the metro train is substantially lower than for the wheels of a freight wagon. Moreover, it is found that the first axle on the metro train is exposed to higher cooling levels than the remaining axles. In a numerical example, temperatures of tread braked wheels are calculated using the new findings for a metro train, and the results obtained are compared with wheel temperatures as calculated assuming freight wagon conditions.
  PubDate: 2014-01-12T22:39:49-08:00
  DOI: 10.1177/0954409712470608|hwp:master-id:sppif;0954409712470608
  Issue No: Vol. 228, No. 2 (2014)