• International Journal of Railway
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• v.1 no.2
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• pp.31-36
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• 2008

$DF_{21}$ diesel locomotive was designed to satisfy the requirement of Kunming Meter track and the 2Co self-guided radial bogie was used to suit the complex curve track. There are totally 12 locomotives was served on the track. The first two locomotives were devotion running on the track since April 2003, the wheel tread splling was occurred on the middle wheel set of the two locomotives after running nearly 150 thousands km on the track of the two locomotives at August 2004. The dynamic analysis was carried out to find the reason. The wheel set longitudinal vibration resonance phenomenon was existed on the locomotive dynamic performance, and this was caused by the too big longitudinal stiffness of the journal box bar on the middle wheel set. Wheel set longitudinal vibration resonance maybe an important reason of lead to wheel tread spalling. The corresponding mend methods were put forward from the point of view of wheel set longitudinal vibration resonance. All the wheel tread of the 12 locomotives on the middle wheel set were in good condition and not occurred the wheel tread spalling after the mend till December 2007 after 350 thousands km were finished. The mechanism of the wheel tread splling and corresponding mend method was discussed in detail in this paper.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.966-970
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.5
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• pp.537-542
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.756-763
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• 2007

The majority of catastrophic wheel failures are caused by surface opening fatigue cracks either in the wheel tread or wheel flange areas. The inclined cracks at railway wheel tread are initiated and the cracks are caused by wheel damage-spatting after 60,000 km running. Because the failured railway wheel is reprofiled before regular wheel reprofiling, the maintenance cost for the railway wheel is increased. Therefore, it is necessary to analyze the mechanism for initiation of crack. In the present paper, the combined effect on railway wheels of a periodically varying contact pressure and an intermittent thermal braking loading is investigated. To analyze damage cause for railway wheels, the measurements for replication of wheel surface and the effect of braking application in field test are carried out. The result shows that the damages in railway wheel tread are due to combination of thermal loading and ratcheting.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.95-103
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• 2006

Wheel treads of E.M.U. are usually under a heavy thermal load by brake frictional heat between wheel and brake shoe and damaged by repeated thermal and mechanical loads. To examine the cause of wheel tread damage of E.M.U.'s in service running, a systematic approach has been used. This study is composed of three parts. Frictional heat analysis was conducted in the first part by finite element method. Two kinds of brake shoes in service were considered. In the second part, experimental study was carried out on a brake dynamometer. Temperatures were measured for the two brake shoes. And experimental study in service running E.M.U.'s was performed. Wheel and brake shoe temperatures were measured by using thermocouples and temperature indicating strips. Finally metallurgical characteristics were examined by a SEM/EDS and the cause of the wheel damage was analyzed. It seems that aggregated ferrous component is a main cause of the wheel tread damage.

• Journal of the Korean Society for Railway
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• v.11 no.6
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• pp.524-529
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• 2008

The damaged wheel in railway vehicle would cause a poor ride comfort, a rise in the maintenance cost and even fracture of the wheel, which then leads to a tremendous social and economical cost. The defect initiation and crack propagation in wheel may result in the damage of the railway vehicle or derailment. Therefore, it is important to evaluate the characteristics of the wheel tread. In the present paper, the characteristics of wheel tread based on contact positions, running distance and brake pattern are evaluated. The result shows that the damaged wheel tread is remarkably depended on the contact positions between wheel and rail.

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.423-430
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• 2002

This study was started to develop maintenance technology for wheel tread suitable domestic railway environment. As a pre-study to develop optima] wheel tread, we analyzed the wear characteristics of wheel tread that is being applied to railway rolling-stock in KNR. To analyze wheel wear characteristics. we have conducted the simulation and experiment for passenger rolling-stock and obtained useful datum. Here, we describe some results.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1598-1603
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• 2009

Recently, several wheel for freight car in running had experienced the wheel failure due to fatigue crack, overheat braking and other factors. Severe heating of the wheel during tread braking was believed to be a contributing factor of derailment. It is necessary to evaluate the residual stress in wheel tread. In the present paper, the residual stress of wheel using x-ray diffraction system is investigated. the result shows that the residual stress of wheel is depend on the running distance and wear rate of wheel.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.71-77
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• 2007

The surface of railway wheel tread in wheel-rail system can not be free from wear because of various circumstance such as railway condition, maintenance condition, weather condition, characteristics of wheel surface's geometrical shape, and vehicle suspension's structural characteristics etc. Therefore, the research on wear reduction and maintenance method are very important to ensure the safety of railway vehicle, to improve car comfort and to decrease maintenance cost. In this study, the wear rates of railway wheel have been periodically measured in terms of the running distance of Electrical Multiple Unit which have been currently operated and the microstructure transformation of wheel tread using replication method have been performed. The results show that the relations between the flange wear and tread microstructure are depended on running distance and it will supply basic data on wheel maintenance.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.641-644
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• 2003

The running safety of the rolling stock depends on the design characteristics and the contact condition between wheel and railway. In this study, it is analyzed how equivalent conicity of wheel tread or its characteristics has influence on the running safety.