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Keywords: leaf, blackish layer, wheel-rail, field test, surface analysis, friction coefficient, chemical reaction.

Summary

Leaves on train tracks affect adhesion between wheels and rails, especially in the autumn. When crushed by wheels, leaves form a blackish, adhesion-lowering layer that sticks to the railhead surface and often requires mechanical removal. This problem has been simulated in scaled and full-scale laboratory tests [1,2,3,4,5,6,7].

A Stockholm local traffic track with a long history of adhesion problems was subject to field tests of railhead contamination. Over a year, on five occasions, i.e. June 2008, September 2008, October 2008, November 2008, and March 2009, the friction coefficient was measured using a hand-push tribometer and rail samples were taken and replaced.

ESCA and GD-OES analyses were conducted to determine the composition of the top layer of rail contaminants and hardness was tested using nano-indentation. The results indicate that the blackish layer on the October 2008 sample contains a much higher contents of, for example, calcium, carbon, and nitrogen than do the leaf residue layers and the uncontaminated samples from other occasions. These high element contents are generated from the leaf material, which chemically reacts with the bulk material. The hardness of the blackish layer is one fifth of the non-blackish layer of the same running band. A chemical reaction occurs from the surface to a depth of several microns. The thickness of the friction-reducing oxide layer predicts the friction coefficient and leaf contamination extent.

References

1: E.A. Gallardo-Hernandez, R. Lewis, "Twin disc assessment of wheel/rail adhesion", Wear, 265, 1309-1316, 2008. doi:10.1016/j.wear.2008.03.020
2: C.R. Fulford, "Review of Low Adhesion Research", Rail Safety and Standards Board, UK, 2004.
3: O.A. Cuevas, "Low adhesion in the wheel-rail contact", Doctoral thesis, TUD, Delft, 2010.
4: W. Poole, "Characteristics of railhead leaf contamination", summary report published by Rail Safety and Standards Board, May 2007. doi:10.1243/09544097JRRT111
5: U. Olofsson, K. Sundvall, "Influence of leaf, humidity and applied lubrication on friction in the wheel-rail contact: pin-on-disc experiments", P. I. Mech. Eng. F.-J. Rai., 218, 235-242, 2004. doi:10.1243/0954409042389364
6: U. Olofsson, "A multi-layer model of low adhesion between railway wheel and rail", P. I. Mech. Eng. F.-J. Rai., 221, 385-389, 2007. doi:10.1243/09544097JRRT111
7: P.M. Cann, "The 'leaves on the line' problem: a study of leaf residue film formation and lubricity under laboratory test conditions", Tribol. Lett., 24, 151-158, 2006. doi:10.1007/s11249-006-9152-2

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 98 PROCEEDINGS OF THE FIRST INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 91 A Field Test Study of Leaf Contamination on Railhead Surfaces Y. Zhu¹, U. Olofsson¹ and R. Nilsson² ¹Department of Machine Design, Royal Institute of Technology (KTH), Stockholm, Sweden ²Stockholm Public Transport AB, Stockholm, Sweden doi:10.4203/ccp.98.91 purchase the full-text of this paper Full Bibliographic Reference for this paper Y. Zhu, U. Olofsson, R. Nilsson, "A Field Test Study of Leaf Contamination on Railhead Surfaces", in J. Pombo, (Editor), "Proceedings of the First International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 91, 2012. doi:10.4203/ccp.98.91 Keywords: leaf, blackish layer, wheel-rail, field test, surface analysis, friction coefficient, chemical reaction. Summary Leaves on train tracks affect adhesion between wheels and rails, especially in the autumn. When crushed by wheels, leaves form a blackish, adhesion-lowering layer that sticks to the railhead surface and often requires mechanical removal. This problem has been simulated in scaled and full-scale laboratory tests [1,2,3,4,5,6,7]. A Stockholm local traffic track with a long history of adhesion problems was subject to field tests of railhead contamination. Over a year, on five occasions, i.e. June 2008, September 2008, October 2008, November 2008, and March 2009, the friction coefficient was measured using a hand-push tribometer and rail samples were taken and replaced. ESCA and GD-OES analyses were conducted to determine the composition of the top layer of rail contaminants and hardness was tested using nano-indentation. The results indicate that the blackish layer on the October 2008 sample contains a much higher contents of, for example, calcium, carbon, and nitrogen than do the leaf residue layers and the uncontaminated samples from other occasions. These high element contents are generated from the leaf material, which chemically reacts with the bulk material. The hardness of the blackish layer is one fifth of the non-blackish layer of the same running band. A chemical reaction occurs from the surface to a depth of several microns. The thickness of the friction-reducing oxide layer predicts the friction coefficient and leaf contamination extent. References 1 E.A. Gallardo-Hernandez, R. Lewis, "Twin disc assessment of wheel/rail adhesion", Wear, 265, 1309-1316, 2008. doi:10.1016/j.wear.2008.03.020 2 C.R. Fulford, "Review of Low Adhesion Research", Rail Safety and Standards Board, UK, 2004. 3 O.A. Cuevas, "Low adhesion in the wheel-rail contact", Doctoral thesis, TUD, Delft, 2010. 4 W. Poole, "Characteristics of railhead leaf contamination", summary report published by Rail Safety and Standards Board, May 2007. doi:10.1243/09544097JRRT111 5 U. Olofsson, K. Sundvall, "Influence of leaf, humidity and applied lubrication on friction in the wheel-rail contact: pin-on-disc experiments", P. I. Mech. Eng. F.-J. Rai., 218, 235-242, 2004. doi:10.1243/0954409042389364 6 U. Olofsson, "A multi-layer model of low adhesion between railway wheel and rail", P. I. Mech. Eng. F.-J. Rai., 221, 385-389, 2007. doi:10.1243/09544097JRRT111 7 P.M. Cann, "The 'leaves on the line' problem: a study of leaf residue film formation and lubricity under laboratory test conditions", Tribol. Lett., 24, 151-158, 2006. doi:10.1007/s11249-006-9152-2 purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £110 +P&P)
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