RTR 4/2010 17 Hard rails in tight curves ones, and several short-pitch ones merge into long-pitch ones again too. This has consequences for the mean depths of corrugations, which may fall after initially rising on account of differing numbers of corrugations. It is only once a high corrugation intensity has been reached that the corrugation lengths remain uniform. The characteristic measurement logs are produced from this time onwards, and the mean corrugation depth no longer declines. This point in time has not yet been reached for any of the thirty measurement sections in this particular experimental curve. For that reason, it is difficult to issue a judgment sufficiently supported by facts on the basis of the available mean values alone. The decision on whether or not the time has come for grinding the inner rail is usually taken considering the mean corrugation depth as a comparative parameter. After a period of five years and a load on the track of approximately 150 million gross tonnes, the mean corrugation depth is generally less than 0.10 mm. It is only at two measuring points at the end of the curve that higher values of up to 0.18 mm were measured, affecting the steel grades “370 LHT” and “R 350 HT”. ning metre (-/m) and the corrugation intensity (as a percentage). The parameters of vertical wear (W1, mm), lateral wear (W3 at less than 45°, mm) and the worn area (A, mm2) were recorded throughout the whole of the observation period over the entire length of the curve, as were the highest and lowest values. Diagrams were produced to assist in the interpretation of these wear parameters for each measurement point of the inner and outer rail for each of the individual rail profiles. 3 Results 3.1 Rail corrugations caused by wheel skid At the beginning of the investigation, both short-pitched and long-pitched rail corrugations developed and were irregularly distributed. This confirms a phenomenon that had been observed on earlier occasions. It is only once the corrugations cover the whole of the sections being measured that the corrugation intensity tends towards 100%. In the course of time, the long-pitch corrugations evolve into several short-pitch Corus provided rails of the types “350 SHH” and “380 MHH”, while Voestalpine provided the types “R 350 HT”, “370 LHT” and “400 UHC”. The sequence of the rails (Fig. 2) was computed using a “fairness factor”, which was intended to consider the dependency of wear on the actual position within the curve as accurately as possible and to ensure a fair comparison of the various grades of steel. New welding instructions for these rails needed to be developed at short notice. Looking back with the benefit of five years’ experience of the experimental track, it is now possible to ascertain that the method chosen was indeed a successful one. Even at the time of writing, there is no such thing as a standard solution for the welding of rails made of hard materials. 2 Arrangement and execution of measurements After the test rails had been laid and ground on 27 June 2003, the zero measurements of the whole curve were made by the University of Innsbruck on 2 July 2003. These have since been followed by ten further measurements of the rail corrugations and wear at a rate of two measurements per year (in the winter and summer months), which it was hoped would reveal any influence of climatic environmental conditions. Two measuring points (on the inside and outside) were set up on each of the 60-metre test-rail sections approximately one third and two thirds along each of them. At each of the measurement cross-sections, the top surface of the inner rail was measured over a length of four metres with a Cemafer mechanical longitudinal profile measuring device. The recorded data was digitised and interpreted according to the length of the rail corrugations caused by wheel skid, their depth, their number and their intensity. On each occasion, a measurement was made of track 2 (i.e. at 33 mm from the bolt contact point on the running edge in the direction of the middle of the rail head. The corrugation intensity (expressed as a percentage) is defined as the product of the number of medium-pitch corrugations and the mean corrugation length relative to the measured length and is used as a comparative parameter in the interpretation of the results. The measurement of the wear parameters (vertical and lateral wear) was performed at each measurement cross-section on the inner and outer rail using an electronic transverse-profile measuring device of the “MiniProf” type. The presentation of the values measured on the inner rail is done by indicating the mean corrugation depth (in mm), the mean medium-pitch corrugation length (in mm), the mean number of corrugations per runFig. 2: Arrangement of the sixty-metre experimental rails and numbering of the measurement cross-sections (Diagram: DVV) Fig. 3: Lateral wear on the outer rails of the curve [mm] at the measurement cross-sections along the length of the curve (Source of Figs. 3–5: the authors)
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