• Geomechanics and Engineering
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• v.13 no.1
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• pp.161-171
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• 2017

The underlying ground state of a railway plays a significant role in maintaining the integrity of the overlying concrete slab and ultimately supporting the train load. While effective nondestructive tests have been used to evaluate the rail track system, they can only be performed during non-operating time due to the stress wave generated by active sources. In this study, finite element numerical simulations are conducted to investigate the feasibility of detecting unfavorable substructure conditions by using a moving train load. First, a train load module is developed by converting the train load into time-variant equivalent forces. The moving forces based on the shape functions are applied at the nodes. A parametric study that takes into account the bonding state and the train class is then performed. All the synthetic signals obtained from numerical simulations are analyzed at the frequency domain using a Fast Fourier transform (FFT) and at the time-frequency domain using a Short-Time Fourier transform (STFT). The presence of a void condition amplifies the acceleration amplitude and the vibration response. This study confirms the feasibility of using a moving train load to systematically evaluate a rail track system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.9 s.240
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• pp.1183-1190
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• 2005

This paper presents a dynamic model of railway vehicle for the development of a 6-axis tilting train simulator. The tilting train simulator will be used to verify the tilting electronics and tilting control algorithm that are to be applied to the Korean tilting train. The tilting train simulator is composed of 6 electric-driven actuators, a track generation system, a graphic user interface, and a visualization system with a 1600mm-diameter dome screen. The each system shares the data by means of ethernet network in realtime. In this study, a train model of 9-DOF with a force generation system to tilt train body has been developed. The dynamic analysis for the straight track running and curve negotiation of a railway vehicle can be performed in the model. In this study, a verification study for the application of the model to the simulator has been conducted under curving situation on the track with different radii.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2173-2178
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• 2008

Railroad is the major factor of vibration source in railway vehicles, and it must carefully maintained the original condition to secure the safety and good ride comfort of passenger. Measuring the condition of rail irregularities such as surface, alignment, gauge, twist and cant etc is required to maintain the good performance of railroad. Currently, the various rail irregularity measurement systems(EM120, ROGER1000K and the Total Rail Irregularity Measurement system of Korea High Speed Train) are operated in Korea to estimate the rail irregularity. It is hard to verify the correlation of one rail irregularity data of a measurement system with the other, because they have been adopted different rail irregularity estimation methods. The best method securing the reliability of the irregularity data is the direct confirmation on the ground where the measurement system had detected as a fault section, but it is impossible to apply all sections simultaneously due to limitation of time, labor, cost and equipments. There is a method to secure the reliability of the data by using acceleration values. Rail irregularities, the major factor of vibration in railway vehicle, are transmitted to the vehicle acceleration through masses, springs, dampers and joints as the system dynamic formation. In this study, Transition Function has been adopted by using the rail irregularity and the acceleration value regarding as input & output parameters respectively. It has been verified by comparing the analyzed results with real measured irregularity data from the Total Rail Irregularity Measurement system of Korea High Speed Train. Also various methods has been accomplished to verify the correlation between rail irregularities and acceleration values.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.65-71
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• 2009

In this study, dynamic serviceability of PSC, PreStressed Concrete, simple railway bridge with 25m span was estimated. All of the high speed and general train loads were considered at estimation. Natural frequency is estimated about 8Hz and includes within optimum natural frequency extent of the railway bridge. Also, the bridge was detected that resonance occurrence possibility does not exist. When travel the Moogunghwa train, acceleration response was measured to 0.43g that exceed limitation value 0.35g. Also, rotation angle of girders end did not satisfy design standard of railway bridge for high speed train, but impact coefficient and deflection satisfied design standard. As a result, that railway bridge was detected that is securing dynamic safety and serviceability partially, but methods to decrease vibration acceleration response are required.

• Journal of the Korean Society for Railway
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• v.14 no.5
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• pp.433-441
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• 2011

It is a fact that the straightening of track alignment is one of the undoubted ways to improve the train speed on conventional lines, while that requires huge investment resources. Therefore, the operation of a tilting train as well as the minimum improvement of track is suggested as an effective and economical alternative way for the speed-up of conventional lines. Since a driving mechanism of tilting train is different from those of existing trains, in order to make sure its operation safety and stability on conventional line, the performance of track and roadbed must be preferentially evaluated on the conventional line. Furthermore, it is necessary to estimate the tilting-train-induced roadbed response in detail since the roadbed settlement can lead to the track deformation and even derailment. In this research, the patterns of wheel load and lateral force were monitored and analyzed through the field tests, and the derailment coefficient and degree of wheel off-loading were calculated in order to evaluate the tilting train running safety depending on the running speeds (120km~180km) on the conventional line. Moreover, roadbed pressure, settlement and acceleration were also observed as tilting-train-induced roadbed responses in order to estimate the roadbed stability depending on the running speeds. Consequently, the measured derailment coefficient and degree of wheel off-loading were satisfied with their own required limits, and all of the roadbed responses were less than those of existing high-speed train (KTX) over an entire running speed range considered in this study. As a result of this study, the tilting train which will be operated in combination with existing trains is expected to give no adverse impact on the conventional line even with its improved running speed.

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.363-372
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• 2018

Simulator is used to verifying the function and performance of train control system before verifying with actual train. In this case, it is important that the simulation result should be coincide with the result with actual train. In this paper, the process of the development of automatic train operation (ATO) is described. ATO is in charge of automatic train control such as speed regulation and precision stop control. Identical interfaces from the ATO to the actual train was made in the simulator. Therefore ATO communicates to the simulator in the same way to the actual train. Futhermore, the train dynamic properties was measured by experiments and these were applied to the train model. Hence the response of the train in the simulator to the acceleration command is similar to that of the actual train. The simulation result of precision stop control is compared with the result in the actual train test to show the fidelity of the train model derived in the study and the superiority of this simulator.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.324-333
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• 2014

In this study, physiological status of locomotive engineers were measured through EEG, ECG, EDA, PPG and respiration signals from 6 subjects to evaluate their arousal status during train operating. Existence of tunnels and mechanical vibration of train using 3-axes acceleration sensors were recorded simultaneously and were correlated with operator's physiological status. As the result of the analyzed subjects' physiological signals, mean SCR was increased in the section where more body movement is required. The RR interval was decreased before and after train stop due to the higher level of mental tension. The intensity of beta wave of EEG was found to be higher before and after train stop and tunnel section due to the increased mental arousal and tension. Therefore, it is expected that the outcomes of the physiological signals explored in this study can be utilized as the quantitative assessment methods for the arousal status to be used for sleepiness prevention system for vehicles operators which can greatly contribute to public transportation system safety.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1143-1147
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• 2008

This test is performed to reduce slip/slide which are generated from VVVF inverter. when the adhesive force between wheel and rail is not ensured, slip/slide are mainly originated. In this paper, we carried out real test adopting acceleration changes to find optimized method minimizing the amount of generation of slip/slide. Through this real test, we obtained optimum result on reducing slip/slide and especially focused on decrease in slip. This method is currently applied to real train.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1264-1269
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• 2006

Measurement and estimation of rail irregularity is an important factor to concern travelling safety of train. Now a day, rail irregularity have been measured by EM120 and ROGER 1000K imported from MERMAC Co. Italy and making researches actively in Korea. This paper mainly consider to find correlation between acceleration value of wheel axle in HSR350x and rail irregularity value measured by EM120.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.2
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• pp.121-128
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• 2020

The purpose of this study is to investigate the distribution patterns of displacement and acceleration fields in a nonlinear soil ground based on the interaction of high-speed train, wheel, rail, and ground. For this purpose, a high-speed train in motion was modeled as the actual wheel, and the vertical contact of wheel and rail and the lateral contact, caused by meandering motion, were simulated; this simulation was based on the moving mass analysis. The soil ground part was given the nonlinear behavior of the upper ground part by using the modified the Drucker-Prager model, and the changes in displacement and acceleration were compared with the behavior of the elastic and inelastic grounds. Using this analysis, the displacement and acceleration ranges close to the actual ground behavior were addressed. Additionally, the von-Mises stress and equivalent plastic strain at the ground were examined. Further, the equivalent plastic and total volumetric strains at each failure surface were examined. The variation in stresses, such as vertical stress, transverse pressure, and longitudinal restraint pressure of wheel-rail contact, with the time history was investigated using moving mass. In the case of nonlinear ground model, the displacement difference obtained based on the train travel is not large when compared to that of the elastic ground model, while the acceleration is caused to generate a large decrease.