PSI - Issue 4

Uwe Oßberger et al. / Procedia Structural Integrity 4 (2017) 106–114

111

Author name / Structural Integrity Procedia 00 (2017) 000 – 000

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Fig. 5. (a) 2D sketch in running direction ; (b) sketch of the top view of the crossing; a red line indicates the position of the 2D cross section a as well as the 2D measurements shown in c and d; (c) superposition of 2D profiles obtained at the left wing rail at different times (d) superposition of 2D profiles obtained at the fixed crossing at different times; the insert shows the color code for the 2D profiles as well as the corresponding the summarized average load of the crossing in MGT. As described in a preceding publication by Ossberger et al. (2015) measurements of the crossing geometry were performed right after the installation in track and every 4 to 6 months thereafter for a period of >3 years (still ongoing). In this publication the focus was on the comparison of the performance of different materials in the fixed crossing of a turnout. Fig. 5 sketches the evaluation procedure for 2D measurements taken at the same position of the crossing between April 2013 and November 2015. Fig. 5a is a 2D sketch of the crossing in the main direction, i.e. the straight route and the same direction shown in the picture in Fig. 1. Fig. 5b shows a sketch of the top view of the crossing with a red line indicating the position of the 2D measurements. Fig. 5c and Fig. 5d give plots of the measured profiles at different measurement times. The comparisons of the profiles from the first measurement (blue line) and the last measurement (red line) clearly indicate an ongoing depression/material loss on both the wing rail and the crossing nose at this position. In order to monitor the geometry changes of the whole crossing, 2D sections were measured on 19 predefined positions along the crossing. Subsequently the 3D crossing geometry was reconstructed (for visualization) from the profiles as sketched in Fig. 6. Fig. 6a shows a top view sketch indicating the positions of the individual 2D measurements. Fig. 6b shows the corresponding 3D reconstruction of the crossing. The color bar indicates the local surface change between the first and the last measurement, i.e. within 31 months (4/2013 to 11/2015) in service. The small insert in Fig. 6b illustrates the color code; red regions indicate a surface change (in mm normal to the original surface) that can be interpreted as depression due to plastic deformation combined with material loss due to abrasive wear. Blue regions indicate a surface change that can be interpreted as bulging, i.e. added material with respect to the initial shape, which indicates plastic deformation beside the estimated contact region. Light “blue” regions are noticeable on the left wing-rail in a region of high vertical forces due to wheel transition. Fig. 6c shows an enlarged view of the corresponding area of the same picture given in Fig. 1. As far as the instrumented crossing is part of a left-hand turnout with main traffic in the straight route (see Fig. 1), major geometry changes are observed on the right side of the crossing nose and on the left wing rail. It is also noticeable that higher speeds in the straight route (max. 140 km/h) compared to the diverging route (max. 60 km/h) lead additionally to a higher material loading.