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An Experimental Investigation and Improvement of Insulated Rail Joints (IRJs).

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In this study the effect of sliding speed, applied load and period of time on the wear resistance of end post materials of Nylon12 (N12), Nylon66 (N66), Nylon66a (N66a), Epoxy Glass (EG) and Phenolic Resin Bonded Fabric materials were investigated. Wear tests were implemented in dry and wet conditions on a Block-on-Ring apparatus. The tests were carried out at different sliding speeds of 1.5 m/sec., 3.3 m/sec., and 7.2 m/sec., applied loads of 10 N, 30 N and 50 N, and three periods of time 5 min., 30 min. and 60 min. The obtained results in dry condition tests showed that the wear resistance of Nylon and composite materials used in this study decreases with an increase in applied load and sliding speed due to increase in contact temperature. But the impact of these increases in sliding speed and applied load was less on the wear resistance of composite materials. Unexpected results were that in wet test condition for Nylon66 materials where the wear resistance was less compared with the same material in a dry test.
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14th International Conference on Tribology Serbiatrib ‘15
1
Serbian Tribology
Society
SERBIATRIB ‘15
14th International Conference on
Tribology
University of Belgrade,
Faculty of Mechanical Engineering
Belgrade, Serbia, 13 15 May 2015
AN EXPERIMENTAL INVESTIGATION AND IMPROVEMENT OF INSULATED
RAIL JOINTS
Fathi A. ELSHUKRI¹*, Roger LEWIS²
¹’²University of Sheffield, Sheffield, UK.
*Corresponding author: f.elshukri@sheffield.ac.uk
Abstract: In this study the effect of sliding speed, applied load and period of time on the wear resistance of
end post materials of Nylon12 (N12), Nylon66 (N66), Nylon66a (N66a), Epoxy Glass (EG) and Phenolic Resin
Bonded Fabric materials were investigated. Wear tests were implemented in dry and wet conditions on a
Block-on-Ring apparatus. The tests were carried out at different sliding speeds of 1.5 m/sec., 3.3 m/sec., and
7.2 m/sec., applied loads of 10 N, 30 N, and 50 N, and three periods of time 5 min., 30 min. and 60 min. The
obtained results in dry condition tests showed that the wear resistance of Nylon and composite materials
used in this study decreases with an increase in applied load and sliding speed due to increase in contact
temperature. But the impact of these increases in sliding speed and applied load was less on the wear
resistance of composite materials. Unexpected results were that in wet test condition for Nylon66 materials
where the wear resistance was less compared with the same material in a dry test.
Keywords: : Insulated Rail Joints, End post, Wear, Polymers, Water, Dry, Sliding Wear, Tribology.
1. INTRODUCTION
Insulated rail joints (IRJs) are one of the
essential parts in track circuits. They contains
from two fishplates bolted to each side of the
rail and an insulating material layer (end post)
is placed in the gap between the adjacent rail
ends as can be seen in Figure (1). IRJs are
employed as part of signalling system. They
are used to connect adjoining rails and make
the rail network electrically isolated and
dividing into track circuits [1]. IRJs are
considered to be weak point in the rail track
[2]. IRJs failure is a serious safety case. The
steel parts such as the joint bars and bolts may
break and the rail head material may flow both
due to excessive load from wheels and impact
forces at the IRJs. The end post may crack and
come out of the gap between rails in the joint
which may allow the rails to touch when they
are extended or when the joint is loaded [2-4].
The main failure modes are insulation failures
29% [5]. In a dressing the problem, it is
important to know the reasons that cause
these failures to improve the performance of
insulated joints. One of the reasons that leads
to the damage of end posts is sliding wear. In
this work the sliding wear resistance of five
end post materials: N12, N66, N66a, EG and
PRBF, was investigated. The end post materials
of N12, N66, N66a are classified as
thermoplastic materials and EG and PRBF
materials are classified as thermosetting
materials according to melting point
temperature. The test materials are specified
in Table 1.
14th International Conference on Tribology Serbiatrib ‘15
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Figure 1. Insulated Rail Joints (IRJs) [6].
Table 1. Summary of End Post Material Tested with
Selected Properties.
Material
Density
(g/cm³)
Melting
Point
(C⁰)
Dry
Wet
N12
1.02
232.43
190.98
179
N66
1.14
230.39
131.27
210
N66a
1.20
239.38
194.37
210
EG
1.92
742.65
701.40
-
PRBF
1.35
592.66
547.43
-
2. EXPERIMENTAL DETAILS
2.1 Test Apparatus
Block-on-Ring testing has been used
extensively in the field of sliding wear [7-9].
The ring can represent the “wheel” and the
“block” the end post. Figure 2 displays the
Block-on-Ring rig utilized to carry out the
testing. The maximum speed that can be used
on the rig is 7.2 m/sec. and the minimum
speed is 1.5 m/sec. and 50 N is the maximum
that load can be used. An electrical motor
provided the required velocity via a
transmission belt and six different pulleys that
allow nine different speeds to be achieved.
The test block and ring are loaded together.
The rig was driven at a controlled sliding
velocity with a 100% slip ratio between the
contacting steel ring and specimen block. The
test conditions were compared with the
energy within the contact in the field. In this
case it can be calculated as (normal force x
friction coefficient x slip in the contact) and
scaled via the contact area.
Tγ/A for the rig was 0.084 to 6.20 N/mm². In
the rail head/wheel tread contact typical field
values for Tγ/A are 0 to 10 (N/mm²). The -on-
Ring tests are in the right regime. The volume
loss was determined in the test from the mass
loss and density data.
Figure 2. Block-on Ring Rig
2.2 Specimens
The ring specimens were cut from railway
wheel steel sections. They had a 42 mm
diameter with a contact width of 10 mm as
shown in Figure 3. The surface roughness of
contact surface was 1 micron. The block
specimens were cut from end post N12, N66,
N66a, EG and PRBF materials into 5 mm x 5
mm x 32 mm as shown in Figure 4. The contact
surfaces were ground to a roughness of 1
micron.
Figure 3. Schematic of Ring Specimen
Figure 4. Schematic of Block Specimens
3. RESULTS AND DISCUSSIONS
3.1 Thermoplastic Materials
Nylon 12 Material: the wear resistance of N
12 was affected slightly in the case of
increasing sliding speeds from 1.5 m/sec to 7.2
m/sec at an applied load of 10 N (see Figure 5)
and in case of increasing sliding speeds from
1.5 m/sec to 3.3 m/sec, at a load of 30 N (see
Figure 6). The rubbing surface was partly
Transmission Belt
Speed Pulley
Rig
Test Block
32mm
5 mm
5 mm
42 mm
10 mm
End Post
14th International Conference on Tribology Serbiatrib ‘15
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smooth. Pits and ploughing parallel to the
sliding orientation were observed. The amount
of material removed rose massively in the case
of a sliding speed of 7.2 m/sec, at a constant
load of 30 N. The worn surface was coarse. Pits
and scratches parallel to the sliding direction
were appeared. This was due probably to
adhesive wear. Whilst the amount of volume
loss increased massively when sliding speed
rose to 7.2 m/sec at a load of 50 N as shown in
Figure 7 where the material was melted
(thermal wear) (see Figures 11 and 12). The
thermal wear occurring when material contact
temperature rise over the material melting
point, so the material become very hot and
melt. On the other side, there was a positive
impact of water on the material wear
resistance in wet tests condition where
contact temperature was decreased during the
test which led to increasing wear resistance of
material (see Figures 8-10). The rubbing
surface was partly rough and characterised by
pits, smooth and plough was parallel to the
sliding direction (see Figure 13).
Figure 5. Dry Sliding Test at 1.5 m/sec and 10 N.
Figure 6. Dry Sliding Test at 3.3 m/sec and 30 N.
Figure 7. Dry Sliding Test at 7.2 m/sec and 50 N.
Figure 8. Wet Sliding Test at 1.5 m/sec and 10 N.
14th International Conference on Tribology Serbiatrib ‘15
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Figure 9. Wet Sliding Test at 3.3 m/sec and 30 N.
Figure 10. Wet Sliding Test at 7.2 m/sec and 50 N.
Figure 11. Nylon 12 Melted
Figure 12. Contact Surface of N12 in Dry Test at7.2
m/sec and 50 N.
Figure 13. Contact Surface of N12 In wet Test at
7.2 m/sec and 50 N.
Nylon 66 Material: the material wear
resistance was affected slightly in the case of
increasing sliding speeds from 1.5 m/sec to 7.2
m/sec at an applied load of 10 N (see Figure 5).
The contact surface became smooth and pits,
cracks, waves and scratches parallel to sliding
orientation were appeared across the surface.
The wear resistance of the material was
affected significantly in the case of increasing
sliding velocity from 1.5 m/sec to 7.2 m/sec at
a loads of 30 N and 50 N (see Figures 6 and 7).
The rubbing surface was coarse due probably
to a adhesive wear at sliding speed of 3.3
m/sec and a load of 30 N and the wear surface
became partly smoothened at sliding speed of
7.2 m/sec and an applied loads of 30 N and 50
N due to thermal wear as shown in Figure 14.
While in the case of wet tests, the material
wear resistance was significantly reduced as
seen in Figures 8-10. This could have
happened because:
i) material became weak and strength
reduced.
ii) the absorption of water caused in
decrease of material hardness as shown in
Table 1
iii) chemical corrosion wear increased. This in
agreement with the results obtained by
Wang [10].
The rubbing surface was smoothened and
characterised by scratches parallel to the
sliding orientation as appeared in Figure 15.
Melted Material
Thermal Wear
Sliding Direction
Smearing
Sliding Direction
Ploughing
14th International Conference on Tribology Serbiatrib ‘15
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Figure 14. Contact Surface of N66 in Dry Test at 7.2
m/sec and 50 N.
Figure 15. Contact Surface of N66 in Wet Test at
7.2 m/sec and 50 N.
Nylon 66a Material: there was a slight
influence on material wear resistance when
sliding speed increased from 1.5 m/sec to 3.3
m/sec at a load of 10 N (see Figure 5). The
worn surface was partly smoothened.
Scratches appeared on the surface parallel to
the sliding direction. The effect of a sliding
speed of 7.2 m/sec and a load of 10 N on the
material wear resistance was more than that
in prior cases. The material wear resistance
decreased gradually when the sliding speed
increased from 1.5 m/sec to 7.2 m/sec at an
applied load of 30 N (see Figure 6). The
rubbing surface was rough. This was due to
adhesive wear (when the temperature rise but
lower than the melting point, the material
become hot, hardness decreases and
adhesive/abrasive wear increases). The
material wear resistance was affected
considerably when sliding speed increased
from 1.5 m/sec to 7.2 m/sec at a load of 50 N
as seen in Figure 20 and the wear surface was
smooth (see Figure 16). This was due to
thermal wear. In contrast, there was a positive
effect of water on material wear resistance in
case of wet tests condition compared with dry
tests condition as shown in Figures 8-10. The
wear surface was more smoothened, cracks
were observed and scratches existed on the
surface (see Figure 17).
Figure 16. Contact Surface of N66a in Dry Test at
7.2 m/sec and 50 N.
Figure 17. Contact Surface of N66a In wet Test at
7.2 m/sec and 50 N.
3.2 Thermosetting Materials
Epoxy Glass Material: the material wear
resistance gradually decreased due to an
increase of sliding speed from 1.5 m/sec to 7.2
m/sec at a load of 30 N (see Figure 6). The
worn contact surface was coarse. Fibres and
scratches were observed on the surface. The
wear resistance of the material reduced
significantly when the sliding velocity rose
from 1.5 m/sec to 7.2 m/sec at a load of 50 N
as shown in Figure 7. The wear surface was
more roughened and severe deterioration of
fibre surface was observed due to the rise in
temperature as shown in Figure 18. The
material wear resistance was better in the
case of wet test condition as seen in Figures 8-
10. These happened because contact
temperature reduced. The worn surface
became smooth and the wear damage to be
fibres exposed and scratches parallel to sliding
direction (see Figure 19).
Figure 18. Contact Surface of EG in Dry Test at 7.2
m/sec and 50 N.
Sliding direction
Smearing
Sliding Direction
Scratches
Sliding Direction
Scratches
Sliding Direction
Fibres
14th International Conference on Tribology Serbiatrib ‘15
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Figure 19. Contact Surface of EG in Wet Test at 7.2
m/sec and 50 N.
Phenolic Resin Bonded Fabric Material: the
material wear resistance influenced slightly in
case of sliding speeds of 1.5 m/sec, 3.3 m/sec
and 7.2 m/sec at a constant load of 10 N (see
Figure 5). The rubbing surface was partly
smooth; scratches were formed on the surface.
The wear resistance of the material decreased
gradually when the sliding speed rose from 1.5
m/sec to 3.3 m/sec at a load of 30 N (see
Figure 6). The worn surface became partly
rough due to increase in temperature and
groove marks are appeared on the surface.
While the material wear resistance decreased
massively when sliding speed increased to 7.2
m/sec at loads of 30 N and 50 N as shown in
Figure 20. The worn surface was rough due to
rise in the contact temperature (see Figure 20).
The material wear resistance rose significantly
in case of wet tests condition compared with
that in dry tests condition as seen in Figures 8-
10. The sources of wear damage to fibre,
smears and scratches parallel to sliding
direction as shown in Figure 21.
Figure 20. Contact Surface of PRBF in Dry Test at
7.2 m/sec and 50 N.
Figure 21. Contact Surface of PRBF in Wet Test at
7.2 m/sec and 50 N.
4. CONCLUSIONS
The volume loss data obtained from
experimental work for the studied end post
materials (Nylon 12 N12, Nylon 66 N66, Nylon
66a N66a, Epoxy Glass EG and Phenolic Resin
Bonded Fabric PRBF) using sliding velocities of
1.5 m/sec., 3.3 m/sec., and 7.2 m/sec. and
three different loads of 10 N, 30 N, and 50 N
shows that, the material resistance is affected
by sliding speeds and applied loads in dry and
wet test conditions. All thermoplastic end post
materials have been melted when sliding
speeds and an applied loads rose in the case of
dry test condition. The wear resistance of
thermoplastic materials were improved in wet
test except Nylon 66. The thermosetting
materials did not melt in all test conditions.
Epoxy glass material has higher wear
resistance. Thus the best material from the
end post materials of N12, N66, N66a, EG, and
PRBF which resist the sliding wear in the field
of railway as appearing from the obtained
experimental results in this study is epoxy
glass materials (EG).
Acknowledgment
I would like to extend my sincere thanks
and appreciation to the Ministry of Higher
Education in my home country of Libya for full
financial support for this search.
References
[1] Charlton, Z. I., Innovative Design Concepts
for Insulated Joints, 2007, Virginia
Polytechnic Institute and State University.
Blacksburg, Virginia. p. 232.
[2] Davis, D. D. and Akhtar, M. N., Improving
the performance of bonded insulated joints.
Railway track and structures, 2005. 101(1):
p. 14-17.
Sliding Direction
Scratches
Fibres
Sliding Direction
Rougher
Sliding Direction
Scratches
Smooth
14th International Conference on Tribology Serbiatrib ‘15
7
[3] Chen, Y. C., The effect of proximity of a rail
end in elastic-plastic contact between a
wheel and a rail. Proceedings of the
Institution of Mechanical Engineers, Part F:
Journal of Rail and Rapid Transit, 2003.
217(3): p. 189-201.
[4] Jeong, D. Y., Progress in rail integrity
research, 2001, Federal Railroad
Administration, Office of Research and
Development.
[5] LB Foster, Rail Products. 2009 [cited 2015
January]; Available from:
http://www.lbfoster.com/content.aspx?id
=1452.
[6] RAILFOTO. Insulated Rail Fishplate Joint.
2006 [cited 2015 January]; Available from:
http://railfoto.fotopic.net/p15613474.html.
[7] ASTM, Standard Test Method for Ranking
Resistance of Material to Sliding Wear
Using Block-on-Ring Wear Test, 2010.
[8] Kennedy, D. and Hashmi, M., Methods of
wear testing for advanced surface coatings
and bulk materials. Journal of Materials
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246-253.
[9] Ruff, A., Comparison of standard test
methods for non-lubricated sliding wear.
Wear, 1989. 134(1): p. 49-57.
[10] Wang, J. and Gu, M., Wear properties and
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science, 2004. 93(2): p. 789-795.
... -Elshukri (2015a) [96] és Elshukri (2016a) [97] [110]. ...
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Innovative Design Concepts for Insulated Joints Improving the performance of bonded insulated joints. Railway track and structures
  • Z I Charlton
  • D D Davis
  • M N Akhtar
Charlton, Z. I., Innovative Design Concepts for Insulated Joints, 2007, Virginia Polytechnic Institute and State University. Blacksburg, Virginia. p. 232. [2] Davis, D. D. and Akhtar, M. N., Improving the performance of bonded insulated joints. Railway track and structures, 2005. 101(1): p. 14-17.
Insulated Rail Fishplate Joint
  • Railfoto
RAILFOTO. Insulated Rail Fishplate Joint. 2006 [cited 2015 January]; Available from: http://railfoto.fotopic.net/p15613474.html.
Test Method for Ranking Resistance of Material to Sliding Wear Using Block-on-Ring Wear Test
  • Standard Astm
ASTM, Standard Test Method for Ranking Resistance of Material to Sliding Wear Using Block-on-Ring Wear Test, 2010.