• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.55-63
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• 1995

The flow field around a high-speed train including cross-wind effects has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations in the inertial frame using the iterative time marching scheme. The governing equations are differenced with 1st-order accurate backward difference scheme for the time derivatives, 3th-order accurate QUICK scheme for the convective terms and 2nd-order accurate central difference scheme for the viscous terms. The Marker-and-Cell concept was applied to efficiently solve continuity equation, which is differenced with 2nd-order accurate central difference scheme. The 4th-order artificial damping is added to the continuity equation for numerical stability. A C-H type of elliptic grid system is generated around a high-speed train including ground. The Baldwin-Lomax turbulent model was implemented to simulate the turbulent flows. To validate the present procedure, the flow around a high speed train at constant yaw angle of $45^{\circ}\;and\;90^{\circ}$ has been simulated. The simulation shows 3-D vortex generation in the lee corner. The flow separation is also observed around the rear of the train. It has concluded that the results of present study properly agree with physical flow phenomena.

• Journal of computational fluids engineering
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• v.19 no.1
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• pp.41-46
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• 2014

The aerodynamic drag of high-speed train has been calculated and the effect of bogie side fairing on the aerodynamic drag has been investigated. Computational Fluid Dynamics (CFD) simulation based on steady-state 3 dimensional Navier-Stokes equation has been conducted employing FLUENT 12 and the aerodynamic model of HEMU-430x, the Korean next generation high-speed train under development has been built using GAMBIT 2.4.6. Three types of bogie side fairing configuration, the proto-type without fairing, half-covered fairing to avoid the interference with the bogie frame and full-covered fairing have been adopted to the train model to compare the drag reduction effects of the bogie side fairing configurations and the numerical results yields that the bogie side fairing can reduce the aerodynamic drag of the 6-car trainset up to 7.8%. The aerodynamic drag coefficient of each vehicle as well as the flow structures around the bogie system have also been examined to analyze the reason and mechanism of the drag reduction by bogie side fairing.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.435-442
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• 2004

Tilting train allow the train to pass curve at higher speed without affecting passenger comfort. As the tilting trains run curve track about 30$\%$ higher than non-tilting trains, the centrifugal force and dynamic force will be higher. Therefore it is very important for tilting train to ensure safety against derailment, and to reduce the lateral track forces by applying light-weight design, optimized suspension design and steering mechanism. The 180 km/h Korean Tilting Train(TTX) which is now developing as a part of the Korean National R & D project, was designed and analytically verified to meet these special requirements. This paper describes the analytic study to verify the safety against derailment, especially on the wheel unloading in case of tilting actuation. The severest curve geometry and curving speed was assumed, the tilting control pattern was also assumed as trapezoidal force function applied to tilting bolster and bogie frame. For the comparison, the operation with the speed of tilting train without tilting actuation was numerically simulated and the operation with the balanced speed without tilting actuation was also numerically simulated. Through the numerical simulation of various operating case, we found that derailment quotients, wheel unloading and Q/P was not affected by tilting actuation and that the bogie of TTX was nicely designed to satisfy the safety against the derailment.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.243-246
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• 2005

The weight reduction of carbody stl1lctures is of great concern in developing high speed tilting train for the normal operation of tilting system. The use of composite materials for the carbody structures has many advantages due to their excellent material propel1ies. In this paper, finite element analysis was conducted to verify the safety of the composite structures of Tilting Train eXpress(TTX). A train prototype with carbon/epoxy composite carbody was manufactured to perform static loading tests according to JIS E 7105. The loading tests were simulated by FE analysis to compare with the test results. To obtain more accurate and detailed result of stress distribution in local region of carbody, the submodeling approach was used. The submodeling analysis results showed the high levels of stress concentration occured on window frame part of TTX as the loading test results did.

• Journal of the Korean Society for Railway
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• v.7 no.2
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• pp.77-84
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• 2004

In order to determine the most suitable material system for achieving the lightweight design while fulfilling the design requirements of carbody structures of Korean Tilting Train eXpress(TTX), aluminum carbody. composite carbody, and hybrid carbody combined with aluminum and composite structures were considered in the present study. The finite-element analysis was used to verify the design requirements or the TTX carbody structures with the material system considered in the design stages. The stresses in the carbody structures and deflections of underframe against static load cases were used as design criteria. The results show that the hybrid carbody structures are beneficial with regard to weight savings and structural integrity in comparison to aluminum and composite carbody structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.210-218
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• 2006

This paper has performed static, fatigue and nondestructive test of tilting' bolster frame for Korean tilting train. From the static test, the structural safety was investigated using Goodman diagram. After the static test, the fatigue test were conducted under tilting load conditions. The fatigue test was conducted for $10\times10^6$ cycles. During the fatigue test, the nondestructive tests using magnetic particle and liquid penetrant were performed at $6\times10^6$cycle and $10\times10^6$cycle. From the crack detection tests, it was known that there was no fatigue crack in the tilting bolster.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.548-555
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• 1998

The influences of high speed train on the dynamic responses of steel composite railway bridges are investigated. The bridge system which has two Ⅰ-girder and several cross beams is modeled with plate and frame elements. With assumption of concrete slabs ate fully connected with steel girders, the offset between slabs and girders is modeled using rigid link. The track system is modeled using beams on elastic foundation theory. And, the TGV train is modeled in 2-dimension considering bouncing and pitching motion. And, braking action of vehicle is considered using speed dependent braking function. To investigate the behavior of bridges due to moving trains, parametric studies are performed.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.462-467
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• 2004

In order to determine the most suitable material system which can achieve the lightweight design and fulfill the design requirements of carbody structures of Korean Tilting Train eXpress (TTX), aluminum carbody, composite carbody, and hybrid carbody combined with aluminum and composite structures were considered in present study. The finite-element analysis was used to verity the design requirements of the TTX carbody structures with the material system being considered in the design stages. The stresses in the carbody structures and deflections of underframe against static load cases were checked as design criteria. The results show that the hybrid carbody structures are beneficial with regard to weight savings and structural integrity when compared to aluminum and composite carbody structures.

• 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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• 2007.11a
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• pp.903-912
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• 2007

Faults of rotating parts of a train normally generate unexpected frequency band or impulsive sound[1] which has a period when it moves with a constant speed. The former can be detected by the moving frame acoustic holography method, which visualizes sound field that is generated by a moving and emitting pure tone or band limited noise source. We have attempted to apply the method to the latter case: the periodic impulsive sound which generate different signal compared with what can be measured by the band limited noise. The signal to noise ratio which determines the success of early fault detection must also be studied with the impulsive and moving signal. This research shows how the problems related with these issues can be resolved. The main idea is that periodic impulsive signal can be expressed by infinite set of discrete pure tones. This enables us to obtain lots of holograms that visualize periodic impulsive sound field including noise by using the moving frame acoustic holography method. Therefore holograms can be averaged to improve the signal to noise ratio until having reliable information that exhibits where the impulsive sources are. Theory and experiment by using the miniature vehicle are described [Work supported by BK21 & KRRI].