• Wind and Structures
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• v.32 no.5
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• pp.487-499
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• 2021

The wind-blown sand effect on the high-speed train is investigated. Unsteady RANS equation and the SST k-ω turbulent model coupled with the discrete phase model (DPM) are utilized to simulate the two-phase of air-sand. Sand impact force is calculated based on the Hertzian impact theory. The different cases, including various wind velocity, train speed, sand particle diameter, were simulated. The train's flow field characteristics and the sand impact force were analyzed. The results show that the sand environment makes the pressure increase under different wind velocity and train speed situations. Sand impact force increases with the increasing train speed and sand particle diameter under the same particle mass flow rate. The train aerodynamic force connected with sand impact force when the train running in the wind-sand environment were compared with the aerodynamic force when the train running in the pure wind environment. The results show that the head car longitudinal force increase with wind speed increasing. When the crosswind speed is larger than 35m/s, the effect of the wind- sand environment on the train increases obviously. The longitudinal force of head car increases 23% and lateral force of tail increases 12% comparing to the pure wind environment. The sand concentration in air is the most important factor which influences the sand impact force on the train.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.175-181
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• 2016

This occurs when the unbalanced rotating body is inconsistent with the mass center line axis geometric center line. Wheelsets are assembled by a single axle with two wheels and a rotating body of a running railway vehicle. Owing to non-uniformity of the wheel material, the wear, and error of the wheel and axle assembly may cause an imbalance. Wheelsets will suffer the effects of vibrations due to the unbalanced mass, which becomes more pronounced due to the thin and high-speed rotation compared to the shaft diameter This can affect the driving safety and the running behavior of a rail car during high-speed running. Therefore, this study examined this unbalanced wheel using a railway vehicle multibody dynamics analysis tool to assess the impact of the dynamic VI-Rail movement of high-speed railway vehicles. Increasing the extent of wheel imbalance on the analysis confirmed that the critical speed of a railway vehicle bogie is reduced and the high-speed traveling dropped below the vehicle dynamic behaviour. Therefore, the adverse effects of the amount of a wheel imbalance on travel highlight the need for management of wheel imbalances. In addition, the static and dynamic management needs of a wheel imbalance need to be presented to the national rail vehicles operating agency.

• International Journal of Railway
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• v.3 no.2
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• pp.54-59
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• 2010

In order to develop the deep-underground GTX (Great Train eXpress) in domestic, the running performance analysis of the propulsion system by a variety of route condition must be carried out before studying the specification and the development of the high-speed propulsion system with inverter and traction motor. Then it is necessary to study the running resistance properties of the high-speed traction system for the variety of tunnel type and vehicle organization method at first. In addition, the properties of the power requirement of the traction motors needed to maintain the balanced speed of the high-speed traction system are next studied. We need to study properties of the emergency braking distance caused by the highest operation speed of the high-speed traction system and present the fundamental design technologies to develop the high-speed traction system for the deep-underground GTX. Finally, the paper analyzes the applicability of the conventional Korean Tilting Train eXpress (TTX) propulsion system on the high-speed propulsion system for the deep-underground GTX.

• Advances in Computational Design
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• v.8 no.1
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• pp.1-12
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• 2023

To consider the effects of the increasing speed of next-generation high-speed trains, the existing traffic safety code for railway bridges needs to be improved. This study suggests a numerical method of evaluating the new effects of this increasing speed on railway bridges. A prestressed concrete (PSC) box bridge with a 40 m span length on the Gyeongbu track sector is selected as a representative example of high-speed railway bridges in Korea. Numerical models considering the inertial mass forces of a 38-degree-of-freedom train and the interaction forces with the bridge as well as track irregularities are presented in detail. The vertical deflections and accelerations of the deck are calculated and compared to find the new effects on the bridge arising with increasing speed under simply and continuously supported boundary conditions. The ratios between the static and dynamic responses are calculated as the dynamic amplification factors (DAFs) under different running speeds to evaluate the traffic safety. The maximum deflection and acceleration caused by the running speed are indicated, and regression equations for predicting these quantities based on the speed are also proposed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1437-1443
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• 2013

Railways are currently subject to the enforcement of speed limits for each curve as prescribed by the Railway Operating Rules in Korea. However, research is required to determine the maximum speed of trains passing through each curve that allows them to run without the risk of derailment in relation to the speed enhancement of existing railway tracks. In addition, factors affecting the running safety of railway vehicles can be classified into those in terms of vehicle aspects and those in terms of track aspects. This study sought to analyze the running safety of railway vehicles according to changes in the inclination of the rail from among the factors affecting the enhancement of safety against derailment. To increase the speed of trains passing through curves that have high derailment risk, this study also analyzed the running safety of railway vehicles according to the inclination of the rail and changes in running speed while a vehicle passes through each curve section in both the up and the down train line sections between Namsunghyun and Chungdo, which represent the actual conditions of railway tracks.

• Korean Journal of Applied Biomechanics
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• v.16 no.2
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• pp.9-19
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• 2006

The purpose of this study was to analyze the kinematic variables of the lower limbs joints and the muscle activity for lower limbs during the level and downhill running. The subjects were 6 males of twenties and required to run on the level and downhill which was -7% grade treadmill at 8.3km/h. The running performances were filmed by high speed video camera and EMG signal was gained by ME3000P8 Measurement Unit. Rectus femoris(RF), Vastus lateralis(VL), Gluteus medius(GLU), Biceps femoris(BF), gastrocnemius medial head(GM), gastrocnemius lateral head(GL), Soleus(SO), Tibialis anterior(TA) were selected. The result of this study were as follows: 1. Ankle, knee, hip joint in downhill running showed less movement than the level running but, no significant difference. 2. VL and BF during the support phase in downhill running showed Iess muscle activity than the level running. but RF showed the opposite result. 3. GM, GL, SO adn TA during the supports phase in downhill running showed less muscle activity than the level running.

• Journal of the Korean Society for Railway
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• v.17 no.3
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• pp.165-170
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• 2014

The resistance to motion of the Korean next-generation high-speed train (HEUM-430X) was assessed on the basis of 12 coasting test runs at coasting speeds up to approximately 380km/h. Two different methods, a linear regression method and a time-integral method, were employed to calculate decelerations from the time-velocity data and the time-distance data, respectively, and an equation of resistance to motion was devised from the deceleration data calculated at each time section. The effect of an improvement of the aerodynamic shape on the resistance to motion was investigated, with the results showing that the running resistance was reduced by about 15% due to these improvements. An increase of approximately 28% of the running resistance was also noted when running in a tunnel relative to running through an open field.

• Journal of the Korean Society for Railway
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• v.16 no.2
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• pp.110-116
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• 2013

Track irregularities is one of the key factors influencing the running behavior of trains. In order to ensure safety and ride comfort of train, the criteria for track irregularities should be adequately established regarding vehicle velocity, vehicle characteristics, characteristics of the track recording car, and measurement interval. Also, track maintenance should be carried out thoroughly according to the criteria for managing track irregularities. Numerical analysis was conducted to investigate the influence of track alignment on the running behavior of Korean high speed train(KTX). Various wavelengths and amplitudes of lateral alignment were considered as parameters for this study using the Vampire program, a vehicle dynamics modeling package in railway environment. Derailment, lateral load, bogie acceleration and body acceleration of numerical analysis results due to alignment were investigated. Finally, the influence of the alignment on safety and ride comfort for the KTX was evaluated. This study indicates that alignment irregularities have significant impacts on running safety, and that the criteria used to manage alignment irregularities should be restrictive to ensure the running safety of the KTX.

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.311-317
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• 2013

In railway construction, superimposition of horizontal and vertical curves has critical effects on the running stability and the ride comfort of vehicles as well as on construction costs. In this study, running safety, ride comfort, and track acting forces were analyzed by a numerical analysis using the VAMPIRE program according to cases of superimposition of vertical and horizontal curves. From the analysis results, it was found that running safety, riding comfort, and track acting forces in the case of superimposition of vertical and horizontal curves as well as vertical and transition curves meet all of the criteria. Also, in the case of the superimposition of vertical curves and curvature change between horizontal transition curves and circular curves meet all of the criteria.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.10
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• pp.1903-1914
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• 2011

In this paper, we propose vehicle running characteristic simulator. The developed simulator is configured by two induction motors which are directly coupled with each other. One motor is to simulate the vehicle drive and another motor is to simulate the vehicle dynamic load including running resistance, gradient resistance and adhesive characteristics between rail and wheel. The running characteristics of vehicle are modeled by numerical formulas. These are programed by software of embedded controller. Thus, it is possible to change several running characteristics during the running test freely and instantly. To evaluate the feasibility of the simulator, the experiments on slip and adhesion coefficient are performed. Additionally the adhesion control and speed control of vehicle are tested with simulator. Experimental results show that the simulator can produce the driving characteristics similar to the vehicle system.