• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.977-978
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• 2012

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.643-648
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• 2011

Fatigue crack in most rails take place by rolling contact between wheel and rail in railway industry. Therefore, it is critical to understand the rolling contact phenomena, especially for the three-dimensional situation. In this paper the steady-state rolling contact problem of KTX wheel and rail (UIC60) has been studied with three-dimensional finite element analysis. The variation of contact pressure and contact stresses on rolling contact surface were obtained using the finite element method. The three-dimensional distribution of contact stresses on the contact surface are investigated. Results show that the distribution of shear stress and contact stress (von Mises) on the contact surface varies rapidly as a result of the variation of stick-slip region. The contact stress at the leading edge is greater than at the trailing edge because of stick and slip phenomena.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.112-117
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• 2003

The purpose of this work is to general approach to numerically simulating wear in rolling and sliding contact area between wheel and rail interface based on the analysis of dynamics with general MBS package. A simulation scheme is developed that calculates the wear at a detailed level. The estimation of material removal follows Archard's wear equation which states that the reduction of volume is linearly proportional to the sliding distance, the normal applied load and the wear coefficient and inverse proportional to hardness. The main research application is the wheel-rail contact of Korea High Speed Railway.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.113-118
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• 2009

It is of utmost important that track loads at rail induced by running train was usually obtained for track performance evaluation. A reaction force of track was measured wheel loads and lateral force by strain gauges on the rail, and then it was obtained to derailment coefficient and variational ratio of wheel load from its relationship. In this study, a existing monitoring system methods with many manpower working were reviewed about measurements, process of testing, and how to obtain accurately measured data.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.842-847
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• 2004

This study presents the minimum spring stiffness of resilient track pad considering the safety of running train. A nonlinear static 3-D finite element is used for the modeling of railway superstructure, especially for the reflection of nonlinear resistance of rail fastening system. Moreover, ballast is considered as an elastic foundation. As the input load, eccentric wheel and lateral force are used and they are derived from ' Lateral-force/Wheel-load Estimation Equations '. Analysis results are compared with following two values : allowable lateral displacement of rail head (derived from the geometrical derailment evaluation of wheel/rail) and operation standard value (derived from the field test results of track).

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.369-376
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• 2003

The purpose of this work is to general approach to numerically simulating wear in rolling and sliding contact area between wheel and rail interface based on the analysis of dynamics characteristics with general MBS package. A simulation scheme is developed that calculates the wear at a detailed and various level. The estimation of material removal follows Archard's wear equation which states that the reduction of volume is linearly proportional to the sliding distance, the normal applied load and the wear coefficient and inverse proportional to hardness. The main research application is the wheel-rail contact of Korea High Speed Railway.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.175-181
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• 2016

This occurs when the unbalanced rotating body is inconsistent with the mass center line axis geometric center line. Wheelsets are assembled by a single axle with two wheels and a rotating body of a running railway vehicle. Owing to non-uniformity of the wheel material, the wear, and error of the wheel and axle assembly may cause an imbalance. Wheelsets will suffer the effects of vibrations due to the unbalanced mass, which becomes more pronounced due to the thin and high-speed rotation compared to the shaft diameter This can affect the driving safety and the running behavior of a rail car during high-speed running. Therefore, this study examined this unbalanced wheel using a railway vehicle multibody dynamics analysis tool to assess the impact of the dynamic VI-Rail movement of high-speed railway vehicles. Increasing the extent of wheel imbalance on the analysis confirmed that the critical speed of a railway vehicle bogie is reduced and the high-speed traveling dropped below the vehicle dynamic behaviour. Therefore, the adverse effects of the amount of a wheel imbalance on travel highlight the need for management of wheel imbalances. In addition, the static and dynamic management needs of a wheel imbalance need to be presented to the national rail vehicles operating agency.

• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.231-243
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• 2021

In this paper, a dynamic response mapping model of the wheel-rail system is established by using the support vector regression (SVR) method, and the hierarchical safety thresholds of the subgrade void are proposed based on the reliability theory. Firstly, the vehicle-track coupling dynamic model considering the subgrade void is constructed. Secondly, the subgrade void area, the subgrade compaction index K30 and the fastener stiffness are selected as random variables, and the mapping model between these three random parameters and the dynamic response of the wheel-rail system is built by using the orthogonal test and the SVR. The sensitivity analysis is carried out by the range analysis method. Finally, the hierarchical safety thresholds for the subgrade void are proposed. The results show that the subgrade void has the most significant influence on the carbody vertical acceleration, the rail vertical displacement, the vertical displacement and the slab tensile stress. From the range analysis, the subgrade void area has the largest effect on the dynamic response of the wheel-rail system, followed by the fastener stiffness and the subgrade compaction index K30. The recommended safety thresholds for the subgrade void of level I, II and III are 4.01㎡, 6.81㎡ and 9.79㎡, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.35-41
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• 2010

White Etching Layer(WEL) is a phenomenon that occurs on the surface of rail due to wheel/rail interactions such as excessive braking and acceleration. Rolling Contact Fatigue(RCF) cracks on the surface of rail have been found to be associated with WEL. In this study, we have investigated RCF damages of white etching layer using twin disc testing and fatigue analysis. These tests consist of wheel flat tests and rolling contact fatigue tests. WEL has been simulated by wheel flat test. It has been founded that the WEL with a bright featureless contrast is formed on the surface of specimen by etching. Rolling contact fatigue test was conducted by using flat specimens with the WEL generated by the wheel flat test. It has been observed that two types of cracks occur within the specimen. The contact fatigue test was simulated in 2D elastic-plastic FE simulations. Based on loading cycles obtained from the finite element analysis, the fatigue life analysis according to the thickness variation of WEL was carried out. The longest fatigue life was observed from the thickness of 20um.