• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1099-1107
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• 2009

Numerical simulation and experimental study to evaluate the critical speed of the railway bogie according to the tread inclination of wheel profile were conducted using 1/5 scale model. It has been shown that the results of the critical speed analysis for the scale bogie model is very close to the test results using scale bogie model and the critical speed is decreased in proportion to the increase of equivalent conicity of wheel profile. Results of this study show that the scale model could be applied to research area relating to vehicle stability as an alternative to overcome the experimental problems caused by full scale test on the roller rig.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.473-479
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• 2007

Lateral vibration at the tail of KTX train was found during the acceptance test. In order to settle the problem of lateral vibration, the wheel conicity was changed 1/40 to 1/20. However, we should evaluate the running safety of vehicle with 1/20 wheel conicity because modification of wheel conicity may cause the running performance to be worse and critical speed to reduce. In this paper, we calculate critical speed of KTX bogie as wheel conicity increase and analyze the running safety for KTX that has 20 car trainset formation using VAMPIRE. and compare with the test results of KHST to validate analysis results on high speed line. A analysis results show that critical speed of 0.3 wheel conicity is over 375km/h and curving performance of 1/20wheel conicity is better than 1/40. Also, we examinate the running performance of KTX to check out possibility to increase speed of KTX on conventional line. A analysis results show that it is possible to increase up to 10% the speed of KTX on tangent line but KTX on a curved line should be operated with the speed of conventional train.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.561-567
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• 2018

This study was carried out to improve the ride quality of high-speed electric multiple unit. Through dynamic analysis of the HEMU-430X, the range of the equivalent conicity with a critical speed of 300 km/h was between 0.05 and 0.25. The initial adopted wheel profile of HEMU-430X was S1002. The equivalent conicity of S1002 with the mileage of more than 40,000 km was about 0.033 and it was confirmed that XP55 is more suitable for stable operation because XP55 has the equivalent conicity of over 0.061. In order to improve ride quality of high-speed electric multiple unit, the change of installation angle of the yaw damper was suggested from $7.35^{\circ}$ to $0^{\circ}$. From sensitivity analysis and optimization, the air spring lateral and vertical stiffness was suggested to be reduced by 30% and the secondary vertical and lateral damper damping coefficient was increased by 50%. By applying this, it was expected that the car body acceleration could be improved by about 20% on average. The HEMU-430X's yaw damper installation angle was changed to $0^{\circ}$ and the damping coefficient of the lateral damper was increased by 30%. When the test run was carried out at the speed of 300 km/h on the Kyungbu high-speed line, the vehicle lateral acceleration had improved by 34.3%. The effect of additional improvement measures proposed in this paper will be tested in the on track test. The riding quality improvement process used in this study can be used to solve ride quality problems that can occur in commercial operation of high-speed electric multiple unit in the future.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.13-19
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• 2010

A design method of railway wheel profile with objective function of equivalent conicity considering wheel dimension constraint, two points contact problem between wheel and rail was proposed. New design method shows good results. New wheel profile generated from optimization process shows better dynamic performance compared with initial profile as the purpose of wheel profile design. And to verify the design method with testing the stability of new wheel profile, we conducted a critical speed test for new wheel profile using scale model applied scaling method of railway vehicle dynamics. The result of critical speed test show good agreement with that of numerical analysis. From the above results, it is seen that the design method with objective function of equivalent conicity is feasible and it could be applied to design new wheel profile efficiently.

• Journal of the Korean Society for Railway
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• v.8 no.5
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• pp.490-494
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• 2005

The geometric parameters between wheel and rail change wheel/rail contact geometry characteristics, and this influence dynamic behavior of rolling stock. So, the selections of optimum geometric parameters between wheel and rail is important for planning of railway system. In this study, we have analyzed the influence of geometric parameters like wheel flange-back distance, gage, and rail inclination on the equivalent conicity relating to dynamic behavior. The analyses show the following results. The widening of wheel flange-back distanc, the decrement of gage increase the equivalent conicity and the increment of rail inclination show the sharp change of the equivalent conicity.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.245-250
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• 2010

In this work, the stability and safety analysis are carried out to predict the performance of a next generation high-speed railway vehicle (HEMU-400X). Since the safety of the high-speed railway vehicles is very important, it is meaningful to predict the dynamic performance and stability of the railway vehicles using a numerical model at a railway vehicle design step. The critical speed of the dynamic model depending on the conicity of the wheel is calculated in the stability analysis. The critical speed calculated in this analysis is over 400km/h for the conicity value of 0.15, which is determined on the basis of representative international standard, UIC 518. Also, the lateral and vertical accelerations at several points of the same dynamic model are calculated for the safety analysis. In the simulation, the dynamic model runs at the test speed of 440km/h, which is determined considering a maximum target speed, and the total driving distance is 30km. And those estimated values are less than the allowed maximum acceleration values of UIC 518.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.11 s.188
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• pp.85-92
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• 2006

For the improvement of a conventional railway speed, tilting train(Tilting Train express) is under the development aiming for a maximum speed 180km/h. Compared to the existing conventional rolling-stock, tilting train could take an advantage of speed improvement about $20{\sim}30%$ on curve sections due to the improvement of cowing performance. However, this speed increasement creates a severe load at wheels, thus it is necessary to study the safety of wheel for tilting train preferentially. On the other hand, it is under consideration that the wheel for conventional railway rolling-stock at speeds of 150km/h will be applied to tilting train at speeds of 180km/h. In this paper, we have studied the strength of wheel structure, the geometrical contact characteristics, and the dynamic performance of wheel to evaluate the safety of wheel for tilting train.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.259-263
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• 2004

The running safety of a railway vehicle depends on the design parameters and contact condition between wheel and rail. In this study, the effect of the conicity of wheel tread is analyzed using ADAMS/RAIL software on running situation. Modal analysis shows in 0.6 Hz natural frequency of lateral mode in fully arranged the KTX cars. The excessive vibration of the tail cars occurs in the 17th car as the speed and the stiffness of the secondary suspension increases, and especially for 1/40 conicity of the GV40 wheel. Also, the analysis shows that combination of wheel profile, GV40 for power cars and XP55 for passenger cars can reduce the lateral vibration of the tail cars.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.230-235
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• 2009

We have conducted an experimental study to analyze characteristics of the wheel profile wear and an influence of the wheel flange wear on the vehicle's vibration characteristics. In experiment with EMU, wheel profile wear is severe at the beginning of the commercial operation. In this stage, the variations of the wheel dimension parameters and equivalent conicity is changed rapidly. Along with a mileage of the test vehicle, the wear of the wheel flange is increased and also the vibration level of the car-body is increased. The peak-peak mean value of the body vibration is estimated as good level, but the level is approached at the limit of the good level as mileage increases. Especially, the peak-peak maximum value of the body vibration shows the distinct increase of vibration level.