• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.339-344
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• 1999

In this paper, the hardness and wear characteristics of the head hardened rail, which is made by thermite and gas pressure weldings have been presented. In general, the wear rate of the gas pressure welded rail is high and uniform compared with that of thermite welded rail. The results indicate that HH 370 welded rail shows stable in hardness and low wear rate compared with other two welded rails. The hardness of head hardened rails shows uniformly distributed along the welded zone, thermally affected zone and a base matrix.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2830-2837
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• 2011

In this paper, a flexible track modeling of turnout was developed and dynamic characteristics of turnout rails were analyzed when a vehicle passed through the turnout. The flexible track modeling is effective to the stiffness and durability design of turnout, because it can capture the deformation and dynamic stress due to the collision of between wheels and rails when the vehicle move to the tongue rail. Also, a more accurate running safety can be obtained by considering the interaction between wheel and rail deformation. Solid finite elements were used for variable cross-sections of rails and the variation of rubber stiffness was modeled. The proposed flexible track modeling in this paper was verified to be valid by comparison with the experiment of the turnout system.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.505-515
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• 2009

In railway bridges, various loads including train load, transverse load and braking force are applied to continuous CWR or semi-continuous longer rail located on non-continuous bridge superstructures. The rail-girder interaction due to thermal expansion is also very complex in railway bridges because the thermal characteristics for each of the rails and girder are quite different. Recently, the bridge retrofits for seismic loads were performed on bridges not designed for these loads. These retrofits may however have limitations with respect to rail-girder interactions because, in general these retrofits address issues related only to seismic loads. In this study of seismic evaluations for railway bridges, the load effects on the bridge rails from the road beds through the continuous rails shall be considered. Practical methods will be proposed which will increase the railway stability. For this, rail-girder interaction analyses due to train loads, temperature changes and seismic loads were performed and the results reviewed from a practical point of view.

• Journal of the Korean Society for Railway
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• v.6 no.1
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• pp.58-65
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• 2003

Wheel/Rail geometric constraint relationships, such as effective conicity and gravitational stiffness, strongly influence the lateral dynamics of railway vehicles. In general, these geometric contact characteristics are nonlinear functions of the wheelset lateral displacement. There is a need to develop a wheel/rail geometric contact simulation program for wheels and rails with arbitrary profiles for the prediction of the dynamic behavior of railway vehicles. An algorithm to simulate any combination of wheels and rails is employed and a GUI for easy analysis is constructed. The simulation program is applied to KTX which will run on both KTX and conventional rails, two rail standards having different rail profiles. The results show that the two rail systems have different geometric contact characteristic

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.645-650
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• 2003

Wheel/Rail geometric constraint relationships, such as effective conicity and gravitational stiffness, strongly influence the lateral dynamics of railway vehicles. In general, these geometric contact characteristics are nonlinear functions of the wheelset lateral displacement. There is a need to develop a wheel/rail contact simulation program for wheels and rails with arbitrary profiles for the prediction of the dynamic behavior of railway vehicles. An algorithm to simulate any combination of wheels and rails is employed and a GUI for easy analysis is constructed. The simulation program is applied to KTX which will run on both KTX and conventional rails, two rail standards having different rail profiles. The results show that the two rail systems have different geometric contact characteristic

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.270-272
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• 2005

With the wide spread of direct current (DC) electric railroads in Korea, the stray currents from negative return rails become a pending problem to the safety of nearby underground infrastructures, such as gas pipelines, water distribution lines, heat pipelines, POF cables, etc. The mitigation of such interference, however, is mainly dependent on stray current drainage bond methods, which connect the underground metallic structures to the negative feeder cables attached to the rails with diodes (polarized drainage) or thyristors (forced drainage). Despite some merits of these methods, they increase the total amount of stray currents from rails and cause other interference problems. In this paper, we summarize the domestic conditions of stray current interference and describe a conceptual design of other mitigation methods for such interference.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.497-504
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• 1998

The manufacturing processes of the head hardened rails and the principles of the heat treatment for carbon steels are introduced in this paper, To get the good wear resistance of the rail, many kinds of microstructure had been developed for the rail head hardening. One of these is the tempered martensitic structure, which is very hard but brittle because of Quenching-Tempering Process. Another is the fine pearlitic structure by Slack Quenching. Now Banitic structure steels are emerging as a potential new material to replace eutectoid pearlitic steels for rail. The main reason of this change is due to the limitaion of pearlitic microstructure with regard to mechanical properties and wear resistances of railway rails.

• Journal of the Korean Society for Railway
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• v.6 no.2
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• pp.81-86
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• 2003

This study proposes the neural network simulator for the integrity evaluation of weld zone in railway rails. For these purposes, the ultrasonic signals for defects(crack) of weld zone in frames are acquired in the type of time series data and echo strength. The detection of the natural defects in railway truck is performed using the characteristics of echodynamic pattern in ultrasonic signal. And then their applications evaluated feature extraction based on the time-frequency-attractor domain(peak to peak, rise time, rise slope, fall time, fall slope, pulse duration, power spectrum, and bandwidth) and attractor characteristics (fractal dimension and attractor quadrant) etc. The constructed neural network simulator agrees fairly well with the measured results of test block(defect location, beam propagation distance, echo strength, etc). The Proposed neural network simulator in this study can be used for the integrity evaluation of weld zone in railway rails.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.821-831
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• 2013

As a result of recent research, it is reported that the periodic replacements criterion of rails is able to extend as grinding rail surface and using the continuous welded rail (CWR). In this study, we carried out fatigue tests on existing laid rails. Based on the test results, an S-N curve expressing the remaining life of laid rails at a fracture probability of 50% was obtained using weighted probit analysis suitable for small-sample fatigue data sets. As rails used for testing had different histories in terms of accumulated tonnage, the test data were corrected to average out the accumulated tonnage. We estimated the remaining service lives for laid rails on the urban railway using equations developed in the past to estimate rail base bending stress and that surface irregularities into consideration. Therefore, estimating the remaining service life of laid rails showed that the rail replacement period could be extended over 200 MGT, although it is necessary to remove longitudinal rail surface irregularities at welds by grinding. Also, the fatigue test results under fatigue limit, Haibach's rule appling half slope of S-N curve under the fatigue limit was considered more reasonable than modified Miner's rule for estimating rail fatigue life.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.767-774
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• 2007

Even though a constant repeated load is applied, plastic deformation may cumulate. This kind of behavior is called ratcheting. Ratcheting may lead to cracks and finally to failure of the rail. Usually ratcheting occurs on high rails in curves. Ratcheting is influenced by residual stresses, wheel-rail contact stresses, thermal stresses due to wheel/rail rolling contact, shear strength of the rail, strain hardening behavior, etc. In this study, contact stresses and thermal stresses are examined. It is found their value is considerable compared to the maximum contact pressure.