• Journal of the Korean Society for Precision Engineering
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• v.32 no.7
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• pp.603-609
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• 2015

Railway vehicles driven by wheels obtain force required for propulsion and braking by adhesive force between wheels and rails, this adhesive force is determined by multiplying adhesion coefficient of the friction surface by the applied axle load. Because the adhesion coefficient has a peak at certain slip velocity, it is important to determine the maximum values of the friction coefficient on the contact area. But this adhesive phenomenon is not clearly examined or analyzed. Thus we have developed new test procedure using the scaled adhesion test-bench for analyzing of the adhesion coefficient between wheel and rail. This adhesion test equipment is an experimental device that contacts mutually with twin disc which are equivalent to wheels and rails of railway vehicles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1207-1218
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• 2013

It is difficult to predict derailment with the existing derailment coefficient like Nadal's formula which is based on the contact forces between one wheel and rail. A new derailment coefficient model developed on a wheelset is able to make a better estimate about the climb derailment, slip derailment, roll over derailment, and mixed derailment types of these. Moreover, not only the mechanical factors considered in the existing derailment coefficients but also other various factors affecting derailment such as wheel unloading and loading, diameter of wheel, and locations of axle-box bearings can be covered with this new derailment coefficient model. That is, the derailment patterns which couldn't be solved with the existing formulas such as Nadal's and Weinstock's models can be analyzed with this wheelset derailment coefficient model because of considering various factors causing derailment. Finally, the validity of the new derailment coefficient model is verified using dynamic model simulations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.12 s.117
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• pp.1231-1237
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• 2006

The vibration of a running railway vehicle can be classified on lateral, longitudinal and vertical motions. The important factor on the stability and ride quality of a railway vehicle is the lateral motion. The contact between wheel and rail with conicity influences strongly on the lateral motion. In this study, an experiment for the vibration of a running railway vehicle was performed using a of the scale model of a railway vehicle. Also, the effects on the car-body, bogie and wheelset were examined for the weight and the stiffness of the second suspension system. The experimental results showed that the lateral vibration increases as the wheel conicity and stiffness of the second suspension system increase. And the lateral vibration of the bogie increases as the mass ratio between car-body and bogie increases. Also, the lateral vibration of the wheel becomes high at low speed, while the wheel of 1/20 conicity makes severe vibration at high speed running.

• International Journal of Railway
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• v.5 no.4
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• pp.156-162
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• 2012

When a vehicle passes through turnout, it is required to minimize the changes of lateral force for running safety of vehicle. Therefore, it is necessary to analyze interaction between the vehicle and the turnout in order to estimate the lateral force and the derailment coefficient on the turnout. In this paper, analysis model of the vehicle and turnout are established and analysis is carried out when the vehicle passes through turnout in order to improve running safety of the vehicle on turnout. To verify the vehicle and turnout analysis model, the contact points between wheel and rail and the influence of changing cradle and tongue rail are also discussed.

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.250-255
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• 2002

The transition between bridge and earthwork often causes the problems of maintenance. The damages of the track on the transition area influence running safety of train and serviceability, increase the maintenance cost. Therefore it is very important to evaluate the dynamic responses of transition and take a efficient measure. In order to evaluate the dynamic behavior of track, the field estimations are performed at the transition area of a conventional line between bridge and earthwork. And the track system on the transition area numerically analyzed to evaluate the dynamic behavior of damaged track with void sleeper. The measured values and Analysis results such as wheel contact force, rail stress, displacement acceleration and track irregularity in the transition area show the dynamic forces are severe. So it is recommended that the transition area should be improved the rigidity by reinforcing the rail.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.755-762
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• 2004

Dynamic analysis of the KTX can predict the dynamic motions in test drive. In this study an analytical model of the KTX is developed to find the critical speed. The numerical analysis for the nonlinear equation motions of 17 degrees of freedom shows the running stability and the critical speed due to the hunting motion of the KTX. Also, the vibration modes of the KTX are calculated using the ADAM/RAIL software, which show that the critical speed occurs for the yawing modes of the car body and the bogie. Finally, this paper shows that the critical speed of the KTX could be changed with the modifications of the design parameters of wheel conicity or wheel contact length.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.836-842
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• 2001

The more sophisticated patterns of propagation model is presented in this paper, which includes three different source characteristics. The spherical, cosine and dipole radiation characteristics compared and sound event level and the maximum sound level are calculated by experiment and calculation. It is shown that patterns of propagation has dipole characteristics for low speed range(below about 150km/h) at electric multiple system. We know that push-pull high speed system(maximum speed: 300km/h) has cosine characteristics of noise propagation. For this purpose, We conduct the experiment of noise and know the empirical formula of noise level and radiation coefficient K. This model of simulation is conducted through point source array model at wheel/rail contact point by using program and experimental formula. We can guess prediction of profile, flat and wear of wheel by above modeling in near field.

• Journal of the Korean Society for Railway
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• v.8 no.5
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• pp.444-453
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• 2005

The safety evaluations of railway wheelsets make use of the static fracture toughness obtained in ingot materials. The static fracture toughness of wheelset materials has been extensively studied by experiments, but the dynamic fracture toughness with respect to wheelset materials has not been studied enough yet. It is necessary to evaluate the characteristics of the fracture mechanics depending on each location for a full-scale wheelset for high-speed trains, because the load state for each location of the wheelset while running is different the contact load between the wheel and rail, cyclic stress in the wheel plate, etc. This paper deals with the fracture toughness depend on load rates. The fracture toughness depending on load rate data shows that once the downward curve from quasi-static values was reached, subsequent values showed a slow increase with respect to the impact velocity. This means that dynamic fracture toughness should be considered in the design code of the wheelset material.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.93-97
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• 2010

Wheel skids may occur during train operations due to low adhesion at the wheel-rail contact point abnormally, and the skids, in turn, result in flats appearing on the wheels, which affect safety and ride comfort significantly. Thus, anti-skid control has a crucial role for safe braking and prevention from flats that could cause a disastrous train accident. This paper presents simulation studies on an anti-skid control unit (ASCU) with a brake system of a rolling stock including a pneumatic model for brake power supply and dump valve operation.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.755-761
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• 2003

The dynamic analysis of the KTX can predict the dynamic motions which occurred in test drive. In this study an analytical model of the KTX is developed to find the critical speed. The numerical analysis for the nonlinear equation motions of 17 degrees of freedom show the running stability and the critical speed due to the hunting motion of the KTX. Also, the vibration modes of the KTX are calculated using the ADAMS/RAIL software, which show that the critical speed occurs for the yawing modes of the car body and the bogie. Finally, this paper shows that the critical speed of the KTX could be changed with the modifications of the design parameters of wheel conicity and wheel contact point.