• Proceedings of the KSR Conference
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• 2003.10c
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• pp.85-90
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• 2003

Among rail defects, the transverse crack, which has been the most dangerous fatigue damage, is developed from shelling near the rail running face and grows perpendicular to the rail surface. Moreover, the crack has occurred frequently fatigue damage during winter. Therefore, to assure the safety of railway vehicles, it is necessary to investigate growth behavior of transverse crack for rail steel. In this study, fatigue crack growth behavior of rail steel and its gas pressure welded part at room and low temperature are performed. The fatigue crack growth rate of the welded part was lower than that of the base part within a lower ${\Delta}K$ region at both room and low temperature, and this difference decreases with increasing the ${\Delta}K$ due to the decrease of the fracture toughness.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.576-579
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• 2014

Rails are continuously exposed to severe environments due to increases in train service frequency, passing tonnage, and speed. Wear is one of the most common types of damage observed on rails. The surface of railsis heat treated to secure safety at critical sites, such as curved tracks or turnouts. Ultrasonic nanocrystal surface modification (UNSM), a new approach for rails, was examined to strengthen the rail surface. The effect of UNSM on the wear resistance of rail specimens was compared with that of heat treatment. Wear resistance was improved after UNSM treatment due to increased hardness and surface compressive residual stress.

• Journal of the Korean Society of Safety
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• v.26 no.3
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• pp.1-7
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• 2011

Fatigue damage on the train wheel surface was estimated by considering the effect of friction coefficient of rolling on the contact surface between the wheel and rail during operation. From FEM analys, the maximum Tresca stress was 550.7 MPa at a depth of 2.07 mm under the maximum contact pressure ($P_{max}$ = 894.3 MPa) between wheel and rail. The maximum stress continued to increase along with the increase in the frictional coefficient. The fatigue initiation lifetime of the wheel by the rolling contact was predicted using the Smith-Watson-Topper (SWT) equation and the maximum principal strain equation (${\varepsilon}$-N).

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.115-118
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• 2007

The geometry of wheel and rail profiles is the primary contributor to wheel and rail interaction. These profiles interact to influence truck steering, vehicle lateral stability, wheel/rail wear and surface damage. Maintaining good control of the profiles is one of the keys to ensuring preferred wheel and rail interaction. Transportation Technology Center, Inc., Pueblo, Colorado, is developing an automated measurement system for wheel/rail contact condition inspections supported by AAR(Association of American Railroads). The system uses a modified version of $WRTOL^{TM}$ (Wheel/Rail Tolerances)--software that performs extensive analysis of wheel and rail contact conditions

• International Journal of Railway
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• v.5 no.2
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• pp.71-76
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• 2012

Recently, axle load, operating speed and traffic density on railroads have had a tendency to increase and thereby cause additional pressure applied on used track. These operating conditions frequently result in service failure due to wear caused by wheel-rail contact and fatigue damage under cyclic loading. Among rail defects, the transverse crack, which has been the most dangerous type of fatigue damages, is developed from the subsurface crack near the rail running face and grows perpendicular to the rail surface. Therefore, it is necessary to investigate systematically the growth behavior of transverse crack for rail steel under mixed mode. In this study, the fatigue crack growth behavior of the transverse crack in rail steel was experimentally investigated under mixed-mode variable amplitude loadings.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2153-2162
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• 2011

The goal of this Paper is to reduce rail's wear in curved track by applying an additional surface layer material(High hardness and High resistance capacity of wear) on the top of the railhead. In order to evaluate appropriation of a coating material, experimental tests such as the varieties of fundamental properties tests (hardening, wear, tensile, and bending) and RCF(rolling contact fatigue)test were performed to establish fatigue wear and damage mechanism. As a result, wear performance of coating rail is better than heated rail about 6times and normal rail about 8~9times.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.541-549
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• 2016

Rolling contact fatigue and wear on rails are inevitable in railway operations due to excessive wheel-rail contact stress. The wear is influenced by vehicle speed, contact pressure, environmental conditions, and many other factors. Speeding on a curved track causes many problems such as wear on the gauge of the rail and rolling contact fatigue. Managing environmental conditions can reduce problems on the wheel and rail interface. In this study, the wear characteristics of wheel and rail materials were investigated by twin-disc testing using various parameters. The results of the wear test indicated that the wear rate under dry conditions was larger than that under wet conditions. We found that contact fatigue damage occurred on the rail in dry conditions, however, the surface of the specimen under water remained smooth. Also, the friction coefficient in dry conditions was larger than in wet conditions.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.318-325
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• 2005

In present, KTX's wheel is worn inevitably according to the interaction with rail in service. It was analyzed by wearing type, damage type and wheel reprofiling cycle on the running surface. As a result, damage on the running surface is main cause to reprofile the wheel. Wearing type of wheel is normal and it hasn't reprofiled according to normal wheel wear. As a follow-up result of the whee] defects on the running surface, if the defects size is well managed by periodical inspection, it would be efficient to increase the wheel life.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.50-57
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• 2010

Various installation faults may lie in fasteners in the construction of a direct-fixation track by the top-down method. At an extreme, they may cause excessive interaction between the train and track, compromise the running safety of the train, and cause damage to the track components. Therefore, the faults need to be kept within the allowable level through an investigation of their effects on the interactions between the train and track. In this study, the vertical dynamic stiffness of fasteners in installation faults was measured based on the dynamic stiffness test by means of an experimental apparatus that was devised to feasibly reproduce gap faults. This study proposes an effective analytical model for a train-track interaction system in which most elements, except the nonlinear wheel-rail contact and some components that behave bi-linearly, exhibit linear behavior. To investigate the effect of the behavior of fasteners in gap faults in a direct-fixation track on the vehicle and track, vehicle-track interaction analyses were carried out, targeting key review parameters such as the wheel load reduction factor, vertical rail displacement, rail bending stress, and mean stress of the elastomer. From the results, it was noted that the gap faults in the concrete bearing surface of a direct-fixation track need to be limited for the sake of the long-term durability of the elastomer than for the running safety of the train or the structural safety of the track.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.4
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• pp.65-81
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• 2013

Urban sprawl has been the limits of traffic accommodate and the supply road. Thus, Light Rail Transit(LRT) has been proposed as the best alternative. Owing to landscape damage from construction of LRT, landscape planning should be considered seriously in the urban planning step. This paper therefore seeks to determine landscape improvement direction of LRT pier. First, the methods in this study shared landscape improvement direction type of LRT pier through previous studies such as planting of surface(30%, 60%, 90% planting of surface), graphic(character, commercial advertising, symbol), and surface treatment type(exposed concrete, white painting, pattern dies). Next, respondent evaluated 3D simulated landscape image accordingly shared types by preference and landscape adjectives using in streetscape evaluation. As a result, visual preference was the highest in planting type of surface and the lowest in the surface treatment type. Covering 60%(4.48) in planting type of surface was the highest. Because it is similar to the golden ratio considering the visual principle, we will need to take advantage through the result of this paper. Also, most landscape improvement direction which satisfied with significant level showed a positive effect from landscape improvement. Comprehensively based on these results, it suggests desirable landscape improvement direction of LRT pier in the city for solution of landscape inhibition problem.