• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.250-256
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• 2010

In this paper, an analytical and experimental study is performed in order to determine the effects of interaction between vehicle and bridge superstructure. For this purpose an improved wheel tracking machine and an adequate single span bridge are designed. Results presented in the paper show that wheel tracking machine including moving mass effects can demonstrate more accurate dynamic interaction between vehicle and structure.

• Structural Engineering and Mechanics
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• v.54 no.5
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• pp.1017-1044
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• 2015

This study aimed to investigate the random vibration characteristic of train-slab track-bridge interaction system subjected to both track irregularities and earthquakes by use of pseudo-excitation method (PEM). Each vehicle subsystem was modeled by multibody dynamics. A three-dimensional rail-slab- girder-pier finite element model was created to simulate slab track and bridge subsystem. The equations of motion for the entire system were established based on the constraint condition of no jump between wheel and rail. The random load vectors of equations of motion were formulated by transforming track irregularities and seismic accelerations into a series of deterministic pseudo-excitations according to their respective power spectral density (PSD) functions by means of PEM. The time-dependent PSDs of random vibration responses of the system were obtained by step-by-step integration method, and the corresponding extreme values were estimated based on the first-passage failure criterion. As a case study, an ICE3 high-speed train passing a fifteen-span simply supported girder bridge simultaneously excited by track irregularities and earthquakes is presented. The evaluated extreme values and the PSD characteristic of the random vibration responses of bridge and train are analyzed, and the influences of train speed and track irregularities (without earthquakes) on the random vibration characteristic of bridge and train are discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.125-133
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• 2011

The wear of rubber track being in contact with the road surface is an important subject because it decreases the traction performance and the operating efficiency of tracked vehicle. For the above reasons, many attempts have been made to quantitatively calculate the rubber track. However, it depends on the experimental methods which are highly time- and cost-consuming. Therefore, the numerical simulation approach is highly desirable, but it needs to model the complex geometry and the material behavior in details as well as the interaction with the road surface. In this study, the rubber track and its material behavior are elaborately modeled since these factors are very important in the prediction of the wear rate of the rubber track. Accordingly to the studies on the rubber wear by previous investigations, it has been found that the wear is greatly influenced by the frictional energy. The frictional energy of rubber track is computed by utilizing the 3D finite element analysis of the rubber track, and the wear rate is evaluated making use of the frictional energy and a wear model.

• 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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.328-333
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• 2002

When vehicle travelling along the track which has irregularity such as vertical profile, dynamic forces arise at the Wheel/Rail contact patch by wheel/rail interaction. In particular short wavelength irregularities on dipped joint and small stiffness of connecting rail bring about intense wheel/rail dynamic effects at higher speed. In the paper, a new model for dipped joint rail is developed to study dynamic behavior of track. A cusp behavior on dipped joint was defined by its amplitude and decay factor, which was presented by FRA track classes. The result of case study are presented, which show wheel rail contact force in each track classes, train operation speed and bending flexible rigidity ratio of fishplates which are connecting the rail.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1719-1724
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• 2010

In the areas susceptible to vibration and noise induced by railway traffic such as downtown area and stations under railway lines, the vibration and the structure-borne noise can be solved by floating slab track system separating the entire track structure from its sub-structure using anti-vibration mat or springs. In other countries, the core technologies for vibration-proof design and vibration isolator - one of key components - have been developed and many installation experiences have been accumulated. However, in Korea, since the design technology of system and components are not yet developed, the foreign systems are being introduced without any adjustment. Thus, in this study, the vibration isolator has been developed and its performance are investigated by the dynamic analysis of a station structure under railways lines and the floating slab track system. For this purpose, the loads transferred from the vibration isolator of the floating slab track were evaluated by train running simulation considering vehicle-track interaction, and then the dynamic analysis of station structure subjected to these loads was performed. The dynamic analysis results show that the proposed floating slab track can reduce the vibration of structure by about 25dB compared with that in conventional ballast track without floating system.

• International journal of steel structures
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• v.18 no.5
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• pp.1617-1630
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• 2018

The crucial differences between conventional rail with split-type connectors and continuous welded rails are axial stress in the longitudinal direction and stability, as well as other issues generated under the influence of loading effects. Longitudinal stresses generated in continuously welded rails on railway bridges are strongly influenced by the nonlinear behavior of the supporting system comprising sleepers and ballasts. Thus, the track structure interaction cannot be neglected. The rail-support system mentioned above has properties of non-uniform material distribution and uncertainty of construction quality. The linear elastic hypothesis therefore cannot correctly evaluate the stress distribution within the rails. The aim of this study is to apply the nonlinear finite element method using the nonlinear coupling interface between the track and structural model and to illustrate the welded rail behavior under the loading effect and uncertain factors of the ballast. Numerical results of nonlinear finite analysis with a three-dimensional solid and frame element model are presented for a typical track-bridge system. A composite plate girder, modeled by solid and shell elements, is also analyzed to consider the behavior of the welded rail. The analysis result showed buckling under the independent calculations of load cases, including 'temperature change', 'bending of the supporting structure', and 'braking' of the railway vehicle. A parametric study of the load combination method and the loading sequence is also included in this analysis.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2263-2268
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• 2011

THE VIBRATION MODE OF RAILWAY VEHICLE IS DIFFICULT TO FIND OUT THE CHARACTERISTICS OF MOTION DURING THE OPERATION ON THE TRACK BECAUSE THESE HAPPEN TO INDEPENDENCE OR DUPLICATION MOTION CAUSED BY VEHICLE, WHEEL/RAIL INTERACTION, TRACK IRREGULARITY AND FAILURE OF THE SUSPENSION & POWER TRANSMISSION DEVICE ETC. IT IS NAMED AN ABNORMAL VIBRATION THAT THE VIBRATION, WHICH WAS PASSED THE PRIMARY AND SECONDARY SUSPENSION, IS AFFECTED TO THE PASSENGER OR DRIVER WITHOUT DAMPING. THIS PAPER DESCRIBES AN EXPERIENCE EVALUATION TO FIND OUT THE CAUSE OF AN ABNORMAL VIBRATION WHICH WAS HAPPEN AT THE CAB OF POWER CAR IN KTX-SANCHEON TRAINSET WHEN ON RUNNING AT HIGH SPEED ZONE.

• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.175-185
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• 2015

Generally, in the train area, switch tracks have required high reliability because this system is directly associated with derailment. Especially, switch tracks of Maglev vehicles must be moved in terms of the whole geometric characteristics, in which the bogies are encased in the switch track. For this reason, switch track was constructed with steel lighter than concrete girders. But, the steel switch track was weak because of structural vibration as well as structural deformation. Therefore, it is important to predict the levitation stability when a vehicle passes over flexible switch track. The aims of this paper are to develop a coupled dynamic model to describe the relationship between a Maglev vehicle and switch track and to predict the levitation stability. In order to develop the coupled dynamic model, a three dimensional vehicle model was developed based on multibody dynamics; a switch model was made using the modal superposition method. And, the developed model was verified using comparison measured data.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1575-1580
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• 2009

Maglev vehicle has two kinds of suspension system such as a secondary suspension with air-spring and a primary suspension as electromagnetic suspension which composed of electromagnet, magnet driver, controller and sensors. The interaction between each dynamic component of vehicle and track effects the stability and running performance. To achieve the specified performance of vehicle, many various approaches of research were tried, then as the result of these efforts, the first commercial operating with Maglev will start soon. The bogie for revenue service from 2012 has some significant modifications compared to the previous one, and to verify the changes the half prototype vehicle was manufactured and took the running performance test. In this report, we will introduce the stage of manufacturing and report results of dynamic performance tests to verify new concept of bogie mechanism.