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|Title: ||Characterization and tribological studies of rail top materials|
|Other Titles: ||Lu gui ding bu cai liao biao zheng ji mo ca xue xing neng zhi yan jiu|
|Authors: ||Liu, Ka Yi (廖嘉兒)|
|Department: ||Department of Physics and Materials Science|
|Degree: ||Master of Philosophy|
|Issue Date: ||2009|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Railroad rails -- Materials.|
|Notes: ||CityU Call Number: TF258 .L58 2009|
x, 110 leaves : col. ill. 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2008.
Includes bibliographical references (leaves 105-109)
|Abstract: ||Rail corrugation is a wave-type wear of the rail surface. There are short and long
pitch corrugations. Short pitch corrugation displays as an undulation of the rail surface with
typical wavelengths between 25 and 80 mm. For long pitch, wavelengths of up to 1200 mm
have been found. Rail corrugations have a critical impact on the maintenance effort and the
cost of grinding and replacement work is very high. In order to prevent the generation of
rail corrugation, many studies have been reported. However, there are few researches on
long wavelength investigation.
In 2006, the Kowloon-Canton Railway Corporation (KCRC), identified that
undulations with a longitudinal pitch of 3.1 m and a vertical profile of less than 1 mm
probably existed in their rail tracks. The possible existence of these undulations, interpreted
as a form of long wavelength corrugation, has provided the incentives for the present study.
In this research, samples were taken from three different manufacturers (BS 97, DO
02 and PZH 98) to study the topography, morphology and microstructure. In the first part
of this thesis, materials characterization was done to observe whether there was any
structural change near the rail-wheel contact surface of the rail relating to wear. Some
metallurgical investigations as well as the macro- and micro-hardness measurements were
done. X-ray diffraction was used to identify the phase composition of crystalline materials
of the railways. It was found that the microstructures were typical pearlite phase in the core
part and elongated fined pearlite due to plastic deformations at the rail top. The hardness
beneath the surface is higher than that at the core part of the rail. The phase composition of
crystalline materials at the surface of the rails is different from that in the core. While the
surface shows many oxide compounds, the core shows alpha-ferrite and cementite.
The second part of the thesis described wear tests on the three different rails. Dry
wear tests were carried out to compare wear performance of the rail samples using a pinon-
disk machine under 20N, with sliding distance of 600 m at constant sliding speed of 0.1 m/s. Six samples were taken within a four-meter length at regular intervals. The analysis of
wear test showed that the wear mechanism was adhesive and the wear rate of the PZH 98 is
highest among the three railways. In all samples, the wear rate of the disks is higher than
that of the pins.
Undulation was not found to be a dominant feature in this study. Nevertheless, the
present results indicate that the PZH 98 rail has the potential to develop into long
wavelength corrugation, i.e. the undulation problem with KCRC in 2006.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b2374862|
|Appears in Collections:||AP - Master of Philosophy |
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