• Smart Structures and Systems
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• v.23 no.4
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• pp.347-357
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• 2019

A new methodology for mitigation of the wheel squealing is proposed and investigated based on the dithering control. The idea can be applied in railway lines particularly in urban areas. The idea is clearly presented, and applied to a validated model. A full-scale model including the vehicle, curved track and wheel/rail contact is developed in the time domain to analyze the possibility and level of wheel squeal noise. Comparing the numerical results with a field test, the model is validated in different levels namely i) occurrence, ii) squealing frequency and iii) noise level. Two different approaches are proposed a) dithering of the wheel with piezoelectric patches and b) dithering of the rail with piezoelectric stacks. The noise level as well as the wheel responses is compared after applying the control strategy. A parametric study is carried out and effect of the dithering voltage and frequency on the squealing noise is investigated. It is found that both the strategies perform quite effectively within the saturating threshold of piezoelectric actuators.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.467-474
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• 2001

The KNR(Korean National Railroad) is trying to set a new rail standard to back up the speed-up policy of the conventional railways. This work has passably significance since the rail standards used were introduced from Japan without the consideration on our situation. The contact analysis between wheel treads and rail heads, attended with complex calculation and the wear experiments taken long time should be accomplished for the exact investigation to establish a new rail standard. However, this paper just concentrates the structural investigation of the proposed rail standard and the dynamic analysis between trains and rail models with intent to shift the above procedure on the next step.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.409-414
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• 2005

It is difficult to apply the Hertz theory to the wheel-rail contact problem which has the complicated geometric form and plastic deformation. Therefore, we perform the elastic-plastic FE analysis and compare the results with those of Hertz theory. Kalker's simplified theory of rolling contact is used to discretize the contact patches and calculate local traction and slip. The wear volumes are calculated using Archard wear equation.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.637-642
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• 2011

Rails are subjected to damage from rolling contact fatigue, which leads to defects such as cracks. Rolling contact fatigue damages on the surface of rail such as head check, squats are one of growing problems. Another form of rail surface damage, known as "Ballast imprint" has become apparent. This form of damage is associated with ballast particles becoming trapped between the wheel and the surface of rail. These defects are still one of the key reasons for rail maintenance and replacement. In this study, we have investigated whether the ballast imprint is an initiator of head check type cracks and effect of defect size using Finite element analysis. The FE analysis were used to investigate stresses and strains in subsurface of defects according to variation of defect size. Based on loading cycles obtained from FE analysis, fatigue analysis for each point was carried out.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.788-790
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• 1993

In the train position defection for the rail car, which is not able to obtain the short circuit between the track circuit and the wheel, the methods by the inductive radio of non-contact type are applicated. It is represented the principles and the methods of the inductive radio train detection on MLU, Transrapid, HSST, M-Bahn, and People Mover for MAGLEV, on Kobe system for the rubber-tired vehicle, and on ICE for wheel-on-rail.

• Computational Structural Engineering
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• v.22 no.2
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• pp.22-29
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• 2009

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.652-657
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• 2017

The use of continuous welded rail is increasing because of its many advantages, including vibration reduction, enhanced driving stability, and maintenance cost savings. In this work, two different types of continuous welded rails were examined to determine the influence of repeated wheel-rail contact on the crystal structure, microstructure and mechanical properties of the rails. The crystal structure was determined by x-ray diffraction, and the microstructure was examined using optical microscopy and scanning electron microscopy. Tensile and microhardness tests were conducted to examine the mechanical behaviors of prepared specimens taken from different positions in the cross section of both newly manufactured rail and worn rail. Analysis revealed that both the new and worn rail had a mixed microstructure consisting of ferrite and pearlite. The specimens from the top position of each rail exhibited decreased lamella spacing of the pearlite and increased yield strength, ultimate tensile strength and hardness, as compared with those from other positions of the rail. It is thought that the enhanced mechanical property on the top position of the worn rail might be explained by a mixed effect resulting from a directional microstructure, the decreased lamella spacing of pearlite, and work hardening by the repeated wheel-rail contact stress.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.644-647
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• 2013

The important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. The main contributors for rolling noise are the sleepers, rail and wheels. In order to analyze and predict rolling noise, it is necessary to understand the vibrating behaviors of railway tracks, as well as the wheels. In the present paper, theoretical modelings of the railway track are reviewed in terms of the rolling noise, and they are applied for the three representative types of domestic railway tracks operated: the conventional ballasted track, KTX ballasted track and KTX concrete track. The characteristics of waves propagating along rails were investigated and compared between the tracks. The tracks were modeled as discretely supported Timoshenko beams and compared in terms of the averaged squared amplitude of velocity which is directly related to the sound radiation from the rails.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.793-799
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• 2004

In track a third weakness point is joint part, turnout part, curve part. One of them joint part of rail have been known to the most weak point by loosen of joint bar and fish bolt due to impulse and vibration by wheel contact at times. In addition happen to deformation and failure at end of rail, failure and miniature of ballast gravel. Finally impact between wheel and rail become origin cause of a welded rail, noise and vibration. riding condition deterioration, besides track failure. In the present domestic, Thermite and Gas pressure weldings have been used to continuous welded rail(CWR), however stiffness and confidence in quality is lower than Flash butt welding method. FRW have the excellent capacity, however have a shortcoming large scale of machine and power equipment. Therefore we will introduce Mobile Flash Butt Welder can weld in track.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.8
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• pp.1164-1169
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• 2014

Recently, an interest in a hybrid system combining only the merits of the conventional wheel-rail system and Maglev propulsion system is growing as an alternative to high-speed maglev train. This hybrid-type system is based on wheel-rail method, but it enables to overcome the speed limitation by adhesion because it is operated by a non-contact method using a linear motor as a propulsion system and reduce the overall construction costs by its compatibility with the conventional railway systems. Therefore, the design and characteristic analysis of a coreless-type superconducting Linear Synchronous Motor (LSM) for 600km/h very high speed railway system are conducted in this paper. The designed coreless-type superconducting LSMs are the distributed winding model, the concentrated 1 layer winding model and the concentrated 2 layer winding model, respectively. In addition, the characteristic comparison studies on each LSM are conducted.