Abstract
Rail transportation plays a major role in the transportation sector of South Africa and many other countries of the world. Trains are locomotives and carriages that travel on rail tracks. The trains steer with the wheel flange against the inside vertical face of the rail head or crown. This steering action produces wear due to the friction between the two steel surfaces moving relative to one another. It is observed that wear at curves is severe due to the high lateral forces of the wheel flange bearing against the rail crown, with very undesirable economic consequences.
This study investigated steel rail material degradation at play between the sliding and the rubbing surfaces of the wheel flange on track by characterising some worn rail samples from Mayfair, Johannesburg, South Africa, rail line, with the aim to gain a better understanding of their wear mechanism. Chemical composition analysis of steel rail sample was conducted. Hardness and tensile behaviour of steel rail were measured and calculated, respectively. Microstructure features of the worn rail samples were also examined, using the stereoscope, microscope, and the Scanning Electron Microscope. Topography and roughness test analyses were also conducted.
It was discovered that the examined worn out rail, which was originally produced from high carbon steel with pearlites and ferrites microstructure, undergoes a micro-structural evolution to form martensitic structure over the years of usage and exposure to environmental conditions mostly at the surface of the rail, which tends to become brittle. Some welded particles were also found to be interlocked in between the surfaces of the rail, causing gradual degradation and breakdown of the rail. These were caused by pressure shock and impact forces between the movement of the rail and the wheel flange. Hardness tests carried out on the top surfaces of 429, 432 and 591VHN readings of steel rail compared to that of the sub inner part of 359, 352 and 338VHN readings of steel track, found the top-surface to be harder. The surface worn-out particles were found to be oxidised. Topography tests were conducted to consider the roughness rate of steel rail track. Grain size analyses of the surfaces at the top edge of...
M.Tech. (Civil Engineering)