• International Journal of Precision Engineering and Manufacturing
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• v.5 no.2
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• pp.60-67
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• 2004

For improving the motion accuracy of hydrostatic tables, a corrective machining algorithm is proposed in this paper. The algorithm consists of three main processes. The reverse analysis is performed firstly to estimate the rail profile from the measured linear and angular motion error, in the algorithm. For the next step, the corrective machining information is obtained based upon the estimated rail pronto. Finally, the motion errors on the correctively machined rail are analyzed by using the motion error analysis method. These processes are iterated until the analyzed motion errors are satisfactory within the target accuracy. In order to verify the validity of the algorithm theoretically, the motion errors calculated by the estimated rail after the corrective machining process, are compared with those by the true rail which is previously assumed as the initially measured value. The motion errors calculated using the estimated rail show good agreement with the assumed values, and it is shown that the algorithm is effective in acquiring the corrective machining information to improve the accuracy of hydrostatic tables.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.606-612
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• 2008

Creep force is one of the only appeared at conventional train which used to be driven by metallic wheel and rail contact. Due to the elastic deformation of wheel/rail contact patch by the weights of wheel and all the components related to it, creep force generates and becomes to the decision factor of critical speed of bogie(or railway vehicle) which is the criteria of avoiding vehicle to be unstable. There are many kind of factors which affect generation of creep force at a wheel/rail contact surface such as viscosity of contact patch, velocity, wheel and rail geometric profile, mechanical properties of wheel and rail. This paper concentrates on a wheelset simple 2 DOF Equation of Motion being exerted. From the simple numerical analysis using linear solution about getting creep force some factors could find roughly. Among the factors geometric parameter could be the one of most important for this study. In the future we'll prolong the range of study to find out method of measuring creep force easily.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.62-68
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• 2011

This is a testing equipment system to analyze variation of creep force according to wheel-rail tread profile, running speed of vehicle, vertical and lateral force, wheel/rail contact point, attack angle and so on. In this paper, derailment occur in stages until the change of each parameter, while reproducing the actual situation was derailed. Thus, to derail what is the most influencing factors were analyzed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.30-37
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• 2017

When a wheel profile of a train-tram is designed, both train and tram tracks should be considered. This study designed a wheel profile that enables high-speed driving(200km/h) on the train track and low speed driving on the tram track with multiple sharp curves. The study used the approximation optimization method to reduce cost and time, used the sequential quadratic programming method as the optimized algorithm, and the central composite design and response surface method as an approximate model. The optimized wheel shape based on this approximation optimization method reduced wear of the initial wheel showed a better performance in terms of derailment and lateral force.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1069-1077
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• 2008

The railway abrasion measurement system have to satisfy two conditions to increase the measurement accuracy as follows. The laser region which is projected on the rail have to be extracted without the geometrical distortion. The mapping of the acquired laser region data on the rail profile have to be processed exactly. But, the conventional railway abrasion measurement system is deeply effected by the foreign substance( dust, rainwater, and so on ) on the railway or the sensitive response characteristic of the laser to the external measurement circumstance, and then the measurement errors arise from above factors. When the laser region is projected on the rail extracts from the acquired image, the interference of the light with the same frequency as the laser system occurs the serious problems. In the process of the mapping between the railway profile and the extracted laser region, the measurement accuracy is very highly effected by the geometrical distortion and the abnormal variation. In this Paper, we propose the novel method to increase the accuracy of the railway abrasion measurement dramatically. we designed and manufactured the high precision and fast image processing board with DSP Core and FPGA to measure the railway abrasion. The image processing board has the capability that the image of 1024X1280 from camera can be processed with the speed of 480 frame/sec. And, we apply the image processing algorithm base on the wavelet to extract the laser region is projected on the rail exactly. Finally, we developed high precision railway abrasion measurement system with the error range less than +/-0.5mm by which 2D image data is covered 3D data and mapped on the rail profile using the camera model and the perspective transform.

• 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.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.232-237
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• 2008

Several research institutes including KISTEC and KRRI etc., recently, have studied maintenance activities and performance, in order to determine proper maintenance level and maintenance cost of rail tracks. But it may extremely difficult to make a decision in maintenance matters of concrete track and ballast containing other sub-components. For these reasons, this study investigate variables related to current maintenance, essential maintenance, and preventive maintenance. It is intended to suggest estimation method of proper maintenance cost maximizing rail track performance. It is stated that proposed approach may be very useful to make a decision of proper maintenance level. Typical section of rail track is applied for calculation of life cycle cost according to each maintenance strategy. A proper profile for maintenance is determined minimum life cycle

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.539-545
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• 2009

KTX trains which began passenger service between Seoul and Busan in April 2004 have gained very high evaluation for their safe operation. Track is one of the most important means to keep KTX safety, it has not been a fail of safe structure. The track failure during operation may lead to a severe accident. So, it is to be verified the confidence of track maintenance management on the high speed line. This paper would like to find a track deformation trend through a comparative analysis on actual measurement data at these times. It discusses the effect of cyclic dynamic load at welding part. KTX dynamic impact load was measured in accordance with a rail surface irregularity and analyzed some track irregularities according to the condition of rail profile at welding part in the Gyeongbu high speed line.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.473-478
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• 2003

The hydraulic buffer stop placed on the end of the railway brakes the train could not reduce the velocity sufficiently because of the braking system troubles or driver's mistakes. The hydraulic buffer stop is composed of 2 operating parts; hydraulic buffers and rail clamps. Hydraulic buffers brake trains non-destructively in low speed, otherwise rail clamps begin to work in higher speed. In this paper, The braking process of the hydraulic buffer stop is investigated by numerical methods. The hydraulic buffer is numerically analyzed and designed to absorb the kinematic energy of the train below 3.2km/h speed. The hydraulic buffer stop crushed by the train with 5km/h speed is analyzed by FEM package-PAM CRASH in order to obtain the stress profile in rail clamps and buffer stop frame.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1426-1434
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• 2008

This paper addresses the numerical study on the dynamics of the High-speed EMU to enhance the ride quality. The 17 and 34 degrees-of-freedom (DOF) dynamic models for a single railway vehicle are proposed, and its vibrational characteristics according to the nonuniform rail profile are analyzed via Matlab. The validity of the proposed 34-DOF model are verified by comparing its dynamic characteristics and those from ADAMS/Rail. In addition, the critical dynamic parameters are identified by the parametric analysis, and rough design variables to reduce the vibration level of the railway vehicle are proposed. Finally, the frequency analysis - FFT - are conducted to extract the resonant frequencies, which have a significant influence on the determination of the critical speed of the railway vehicle. It is demonstrated that the results from the Matlab-based numerical analysis of the 34-DOF dynamic model are similar to those from ADAMS/Rail.