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Measurement, Interpretation and Classification of South African Track Geometry
Published in Kl. Knothe, St.L. Grassie, J.A. Elkins, Interaction of Railway Vehicles with the Track and its Substructure, 2018
Track geometry is generally defined in terms of track gauge, cross level, alignment, and vertical surface profile. The gauge is defined as the horizontal distance between two rails and is measured between the heads of the rails, at right angles to the rails, and in a plane 14mm below the top of the rail head. Cross-level or cant, is the difference between the elevations of the two rails with twist being the rate of change in cross-level. Alignment is the average lateral deviations of the two rails. and the vertical surface profile or top measurement is the average elevation of the two rails.
A methodology for alignment of measured rail profiles in turnouts as a basis for reliable vehicle/track interaction simulations
Published in Vehicle System Dynamics, 2023
Josef Fuchs, Gabor Müller, Kamil Sazgetdinov, Erich Wipfler, Ingolf Nerlich
In diagnostic vehicles, the track parameters and wear indicators are calculated starting from the measurement of rail profiles by means of contactless optical units. Generally, rail profile measurement systems use structured light vision sensors to measure cross section profiles of rails and calculate wear indicators based on differences of the measured profile data. In [4], a measurement system engineered by Mermec is presented which is used in diagnostic vehicles by the Swiss Federal Railway (SBB). This system consists of a laser diode and a charge-coupled device camera. When the laser line lights the rail profile contour, the camera record the reflected light and can determine the point coordinates of the profile in its reference frame. This described Laser Displacement Method (LDM) is one of the most common methods for rail profile measurements. However, this measurement method can be affected by environmental disturbances like outliers and profile diversity [5]. Outliers are mainly caused by reflections and projections of irrelevant areas (e.g. ballast). Profile diversity is caused by the fact that railway tracks do not contain only plain track zones (largest amount), but also joint and turnout zones. In turnout zones, profiles are more distorted due to the specific geometry conditions (e.g. guard rail area) [5]. In diagnostic vehicles for railway track inspection, these profiles are not considered in the wear assessment due to profile integrity.
Combining wavelet analysis of track irregularities and vehicle dynamics simulations to assess derailment risks
Published in Vehicle System Dynamics, 2023
Mariana A. Costa, João N. Costa, António R. Andrade, Jorge Ambrósio
A common practice among IMs is to use track geometry irregularities, collected by a track recording vehicle (TRV), for safety assessments and maintenance planning and prioritisation. In this study, the deterioration of track geometry is quantified in terms of four main parameters: (1) longitudinal level, (2) lateral alignment, (3) cross level, and (4) gauge. These four parameters are listed in the European Standard EN 13848-5 [7] as some of the main parameters that influence the vehicle response in terms of Y/Q. Figure 2 illustrates these four track parameters. Following Soleimanmeigouni et al. [1], the longitudinal level is the geometry of the track centreline projected onto a longitudinal vertical plane. Lateral alignment is the geometry of the track centreline projected onto a longitudinal horizontal plane. Cross level is the difference in the height of the adjacent running tables computed from the angle between the running surface and a horizontal reference plane. Gauge is the distance between the gauge profiles of two adjacent rails at a given location below the running surface. In terms of measured track irregularities, longitudinal level and lateral alignment are taken as the average between the measured values of the left and right rails, as shown, respectively, in Figure 2(a) and (b), whereas cross level and gauge are taken as the difference between the nominal and the measured values. Figure 2(c) shows the measured cross level as and the measured gauge as .
Formation mechanism of short-pitch rail corrugation on metro tangent tracks with resilient fasteners
Published in Vehicle System Dynamics, 2023
Wei Li, Zhijun Zhou, Xin Zhao, Zefeng Wen, Xuesong Jin
Short-pitch rail corrugation has recently become common on tangent tracks with resilient fasteners in China metro lines. The short-pitch rail corrugation can cause high-frequency wheel–rail vibration, annoying noise and failure of train and track components [1,2]. The resilient fasteners which can isolate wheel–rail vibration have been widely used. Rail fasteners consisting of rubber pads, steel plate and clips are used to connect the rails to sleepers or slabs of track. They not only transfer wheel–rail loads to supporting structures, but also provide appropriate resilience of the track. To reduce the vibration transmission of wheel–rail system, resilient rubber components such as rail pads, rubber wedge or rubber pads are introduced to the fasteners. For the resilient fasteners, the resilient rubber components are softer than those of conventional fasteners which have been mainly used in China metro lines. The main difference between the resilient fasteners and the conventional fasteners is stiffness value of resilient rubbers for the fastener system. For the resilient fasteners in China metro lines, the low vertical stiffness of less than 20 MN/m for the resilient rubbers are provided. For the conventional fasteners, the vertical stiffness of about 40–60 MN/m for the rubbers are used. For recent ten years, three types of the resilient fasteners called ‘Vanguard’, ‘Cologne-Egg’, ‘GJ-III’ have been used to mitigate vibrations in China metro lines. Their values of vertical stiffness are 5∼10 MN/m,10∼12 MN/m and 12∼14 MN/m, respectively. The Vanguard fastener (see Figure 1(a)) supports the rail web and keeps rail floating to provide exceptionally low vertical stiffness [1,3,4]. The Cologne-Egg fastener uses shear deformation of rubber materials to provide low vertical stiffness [5,6]. The GJ-III fastener uses compression deformation of soft rail pad and rubber pad to provide low vertical stiffness [1]. ‘DT’ series including DTVI, DTVII, DTVII2 etc. as the conventional fasteners are mainly used in non-special vibration reduction requirements section in China metro lines [1,3,5,7].