• Journal of the Korean Society for Precision Engineering
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• v.33 no.9
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• pp.739-744
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• 2016

The truck that is used as running equipment for tank freight car support is a core structural part that supports the load of the car body and significantly influences the safety of freights and vehicles, as well as their running performance. Running equipment is composed of truck frames, wheels and wheel axles, independent suspensions, and brakes. Among these components, the truck frame supporting the load of the vehicles and freights may be the most important component. This study was carried out to analyze the structure of truck frames and to determine whether they are safe when the maximum vertical load, braking part load, and the front and rear load are applied to truck frames. This was achieved by subjecting the truck frames to stress tests and then measuring the stress on each part. The results of the stress tests showed that truck frames have a safe vehicle load design.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.183-188
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• 2009

The High speed electrical multiple train having a distributed electrical motor system has just been developing to aim the experimental maximum speed at 400km/h since August, 2007. This project comes in stage of basic design and so, it needs to take some review and analysis the characteristics of suspensions on the view of basic design. The vehicle model for dynamic analysis is made from the concept design model that used for the preliminary design review with Vampire program and it is modeled with three linear secondary dampers and two shear springs separated from the bush elements in previous model. The optimization technique is applied to search the proper range of linear characteristics for the suspension elements to satisfy the stability performance at speed 130m/s (about 460km/h). The results shows there are some optimum points according to the variation of primary and secondary suspension characteristics and it would be useful to make a decision to select the proper suspension elements in the precision design that will be done by the manufacturing company.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.241-247
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• 2008

This paper describes a cause of fire accidents on power system for DC electric traction vehicles. We investigated fire scene of power line for DC electric traction vehicles. From analysis results, the cause of fire on power line turned out line to ground fault between a feeder of electric power services(pantagraph) and DC electric traction vehicle roof. Fire accidents of DC electric traction vehicles be assumed that electric sparks had been produced between the pantagraph and the power line conductor by repetitively making contact and separation, maybe if some material like branches get in between connecting rod it make progress line to ground fault. ZnO arresters are widely used to protect DC electric traction vehicles against overvoltages caused by lightning or switching surges. However, the arresters are deteriorated by commercial frequency overvoltages and/or lightning one. Deteriorated arresters could lead power failures, such as line to ground fault by a thermal runaway resulting from the increases in leakage current even in a nominal power system voltage. The power failures, such as line to ground fault would be causative of the fire accidents.

• Journal of the Korean Society of Visualization
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• v.19 no.2
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• pp.26-31
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• 2021

The spanwise growth of turbulence structures in turbulent pipe flow was investigated using the direct numerical simulation data of Re_𝜏 = 544, 934 and 3008. Two-point correlations and pre-multiplied energy spectra of streamwise velocity fluctuations were examined along the spanwise direction. The arclength direction is defined as r𝛳, which is useful for an analogy with the spanwise direction for channels or boundary layers; here, r and 𝛳 are the radial distance from the core and the azimuthal angles, respectively. Both analyses showed that the arclength scales increased with increasing the wall-normal distance. It showed that the coherent structures were confined in the core region due to the crowding effect of a circular pipe geometry. The pipe flow simulation could describe a realistic geometrical flow along the azimuthal direction, unlike the simulations of turbulent channel or boundary layer flow using periodic boundary conditions along the spanwise direction. The present results provided the spanwise organization of energy-containing motions over a broad range of scales in turbulent pipe flow.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.802-810
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• 2006

For a thorough train control, the precise train position detection is necessarily required. The widely used current way for train position detection is the one of using track circuits. The track circuit has a simple structure, and has a high level of reliability. However trains can be detected only on track circuits, which have to be installed on all ground sections, and much amount of cost for its installation and maintenance is needed. In addition, for the track circuit, only discontinuous position detection is possible because of the features of the closed circuit loop configuration. As the recent advances in telecommunication technologies and high-tech vehicle-based control equipments, for the train position detection, the method to detect positions directly from on trains is being studied. Vehicle-based position detection method is to estimate train positions, speed, timing data continuously, and to use them as the control information. In this paper, the features of GPS navigation and DR navigation are analyzed, and the navigation filters are designed by constructing vehicle-based train position detection method by combining GPS navigation and DR navigation for their complementary cooperation, and by using kalman filter. The position estimation performance of the proposed method is also confirmed by simulations.

• Steel and Composite Structures
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• v.48 no.2
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• pp.207-233
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• 2023

Steel-concrete composite box girder bridges are widely used in the construction of highway and railway bridges both domestically and abroad due to their advantages of being light weight and having a large spanning ability and very large torsional rigidity. Composite box girder bridges exhibit the effects of shear lag, restrained torsion, distortion and interface bidirectional slip under various loads during operation. As one of the most commonly used calculation tools in bridge engineering analysis, one-dimensional models offer the advantages of high calculation efficiency and strong stability. Currently, research on the one-dimensional model of composite beams mainly focuses on simulating interface longitudinal slip and the shear lag effect. There are relatively few studies on the one-dimensional model which can consider the effects of restrained torsion, distortion and interface transverse slip. Additionally, there are few studies on vehicle-bridge integrated systems where a one-dimensional model is used as a tool that only considers the calculations of natural frequency, mode and moving load conditions to study the dynamic response of composite beams. Some scholars have established a dynamic analysis model of a coupled composite beam bridge-train system, but where the composite beam is only simulated using a Euler beam or Timoshenko beam. As a result, it is impossible to comprehensively consider multiple complex force effects, such as shear lag, restrained torsion, distortion and interface bidirectional slip of composite beams. In this paper, a 27 DOF vehicle rigid body model is used to simulate train operation. A two-node 26 DOF finite beam element with composed box beams considering the effects of shear lag, restrained torsion, distortion and interface bidirectional slip is proposed. The dynamic analysis model of the coupled composite box girder bridge-train system is constructed based on the wheel-rail contact relationship of vertical close-fitting and lateral linear creeping slip. Furthermore, the accuracy of the dynamic analysis model is verified via the measured dynamic response data of a practical composite box girder bridge. Finally, the dynamic analysis model is applied in order to study the influence of various mechanical effects on the dynamic performance of the vehicle-bridge system.

• Journal of the Korean Society for Railway
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• v.15 no.1
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• pp.48-61
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• 2012

It is of great importance to assure the running safety, ride comfort and serviceability in designing the floating slab track for mitigation of train-induced vibration. In this paper, for this, analyzed are the system requirements for the running safety, ride comfort and serviceability, and then, the behavior of train and track at the floating slab track including the transition zone to the conventional concrete slab track according to several main design variables such as system natural frequency, arrangement of spring at transition, spacing of spring isolators, damping ratio and train speed, using the dynamic analysis technique considering the train-track interaction. The results of this study demonstrate that the discontinuity of the support stiffness at the transition results in a drastic increase of the dynamic response such as wheel-rail interaction force, rail bending stress and rail uplift force. Hence, it is efficient to decrease the spacing of springs or to increase the spring constants at the transition to obtain the running safety and serviceability. On the other hand, the vehicle body acceleration as a measure of ride comfort is little affected by the discontinuity of the stiffness at the transition, but by the system tuning frequency; thus, to obtain the ride comfort, it is of great significance to select the appropriate system tuning frequency. In addition, the effects of damping ratio, spacing of springs and train speed on the dynamic behavior of the system have been discussed.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.692-700
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• 2007

A trial run of locally-developed tilting train has been in process on Chungbuk line since the test vehicle was first produced. For the system stabilization, interface verification among the systems including track, structure, catenary and signaling system, not to mention the rolling stock, is very crucial. In the area of wayside structure, the stability of track structure and train run shall be evaluated through the review of impact by increased speed by developed train on track structure. The study thus was intended to evaluate the impact on track while a tilting train is running the curve section, which is vulnerable to accelerated train speed. The analysis of tilting train test running the part of Chungbuk line and Honam line was conducted to identify the impact on existing track performance by tilting train. To identify the movement behavior of each part of track while tilting train, high speed train and traditional train (Mugunghwa and freight train) were running the existing line, wheel load, lateral wheel load, rail bending stress, vertical and lateral displacement of rail and vertical displacement of sleeper were compared and analyzed so as to evaluate the expected impact by tilting train for improving the train speed.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.32-39
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• 2013

The next generation high-speed train(HEMU-430X) is Korea's first electric multiple unit type, high speed vehicle resulting from a national R&D project. Tests have been conducted on the Kyungbu High Speed Line running at speeds up to 354.64km/h, and analysis of the dynamic behavior of the train was carried out to evaluate its safety. In this study, a simplified method using an accelerometer(the method specified in UIC 518 OR) was chosen to analyze the safety of the train's dynamic behavior. The section chosen for analysis section was ${\pm}10{\sim}20km/h$ with respect to the maximum speed point. In addition, we analyzed the trend of this dynamic behavior with increasing speed by comparing the analyzed values with those of UIC 518 OR. The dynamic behavior results met the limit values of UIC 518 OR and the study indicates that this trend is predicted to continue at speeds above 354km/h.

• Journal of the Korean Society for Railway
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• v.18 no.5
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• pp.401-409
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• 2015

Defects generated in a railroad track that guides the railroad vehicle have the characteristic of growing fast; as such, the detection technology for railroad track defects is very important because defects can eventually cause mass disasters like derailments. In this study, a speed-up test facility was fabricated to investigate the feasibility of using magnetic flux leakage (MFL) technology for defect detection in a railroad track under speed-up condition; a test was conducted using a railroad track specimen with defects. For this purpose, an MFL sensor head dedicated to the configuration of the railroad was designed and test specimens with artificial defects on their surfaces were manufactured. Using the test facility, a speed-up test ranging from 4km/h to 12km/h was performed and defects including locations were successfully detected from MFL signals induced by defects with enhanced visibility by differentiating raw MFL signals. In the future, it should be possible to apply this system to a high-speed railroad inspection car by improving the lift-off stability that is necessary for speed-up of the developed MFL sensor system.