• Title, Summary, Keyword: Rail stress

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Stress Analysis in the Elastic-Plastic Analysis of Railway Wheels

  • Ashofteh, Roya Sadat;Mohammadnia, Ali
    • International Journal of Railway
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    • v.7 no.1
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    • pp.1-7
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    • 2014
  • Fatigue and wear in wheels is often due to the forces and loading. These certainly have fundamental effects on reducing the wheel life and increasing the costs related to repairing and maintenance. Modeling and stress analysis of a wheel sample existing in the Iranian fleet have been performed in its contact with U33 and UIC60 rails. The results have been reviewed and analyzed in elastic and elastic-plastic phase and under static (railcar weight) and quasi static loads. Moreover, effects of wheel diameter, axle load, wheel material, rail type are analyzed.

Worn Wheel/Rail Contact Simulation and Cultivated Shear Stresses

  • Noori, Ziaedin;Shahravi, Majid;Rezvani, Mohammad Ali
    • Journal of the Korean Society for Railway
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    • v.16 no.2
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    • pp.93-98
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    • 2013
  • Railway system is today the most efficient way for transportation in many cases in several forms of application. Yet, wear phenomenon, profile evolution, fatigue, fracture, derailment are the major worries (financial and safety) in this system which force significant direct and indirect maintenance costs. To improve the cyclic maintenance procedures and the safety issues, it can be very satisfactory to be informed of the state of wheel/rail interaction with mileage. In present paper, an investigation of the behavior of the shear stresses by logged distance is approached, by implementing the field measurement procedure, in order to determine the real conduct of the most important cause of defects in wheel/rail contact, shear stress. The results coming from a simulation procedure indicate that the amounts of shear stresses are still in high-magnitudes when the wheel and rail are completely worn; even though in simulation based on the laboratory measurements of profile evolutions, the stresses become significantly reduced by logged distance.

Optimal Structural Design for the Electro-magnectic Launcher (전자력 발사기의 최적 구조 설계)

  • 이영신;안충호
    • Computational Structural Engineering
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    • v.9 no.2
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    • pp.143-151
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    • 1996
  • The optimal design for Electro-magnetic Launcher (EML : Rail Gun) considering structural and electrical constraints are presented. For the structure of EML under high pulsed currency, the cross section is minimized subject to maximum stress of each element(rail, side wall, ceramic, and steel) within allowable stress and preload limits. The electrical constraint is the effective ceramic thickness which prevents the eddy current effect reducing the performance of EML. The stress analysis and optimization procedure of 90mm EML is conducted with ANSYS Code. The optimal design under preload is reduced to 53% of area compared with optimal design without preload. In case of rail with arc angle .theta.=45.deg., the performance of EML is the best among the other rail arc angles. The optimal design for rail with arc angle .theta.=45.deg., results in the reduction of 9% of area and 10.4% of deformation compared with Fahrenthold's design. The optimal preload 59.8MPa is much lower than Fahrenthold's design(186MPa). The results show that the optimal design of EML meets the design requirements.

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Bending Fatigue Life Assessment of Aged CWR using the Field Test (현장측정을 통한 노후레일의 휨 피로수명 평가)

  • Park, Yong-Gul;Sung, Deok-Yong;Park, Hong-Kee;Kong, Sun-Yong
    • Journal of the Korean Society for Railway
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    • v.11 no.3
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    • pp.317-325
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    • 2008
  • As a result of recent research, it is reported that the periodic replacements criterion of rails is able to extend as grinding rail surface and using the continuous welded rail (CWR). This study evaluated correlation between conditions of track and load capacity of rail by analysing the dynamic response of track while the metro train is running. Also, it was converted the measured stress waveform into stress frequency histogram by the rain-flow counting methods, and then accumulated fatigue damage ratio and remaining service life of laid rail were calculated so as the apply the equivalence of stress to S-N curve of a new welded rail. Finally, this study suggests a revision of the periodic replacements criterion of CWR, which was based on accumulated passing tonnage, classified by the types and conditions of track system.

Evaluation of Residual Stress of railway wheel (차륜/래일 접촉에 의한 차륜의 잔류응력 평가)

  • Seo Jung-Won;Goo Byeung-Choon;Chung Heung-Chai
    • Proceedings of the KSR Conference
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    • pp.668-673
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    • 2003
  • A wheel and axle failure can cause a derailment with its attendant loss of life and property. The service conditions of railway vehicles have become severe in recent years due to a general increase in operating speeds. Damages of railway wheel are a spalling by wheel/rail contact and thermal crack by braking heat etc. One of the main source of damage is a residual stress. therefore it is important to evaluate exactly. A Residual stress of wheel is formed at the process of heat treatment when manufacturing. it is changed by contact stress developed by wheel/rail contact. Distributions of residual stress vary according to a magnitude of wheel load, a magnitude of friction when acceleration and deceleration. The objective of this paper is to estimate the influence of wheel motion on the residual stress distribution in the vicinity of the running surface.

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Evaluation of Residual Stress of railway wheel (철도차량 차륜의 잔류응력 평가)

  • 서정원;구병춘;이동형;정흥채
    • Proceedings of the KSR Conference
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    • pp.208-213
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    • 2002
  • Railway wheel and axle are the most critical components in railway system. A wheel and axle failure can cause a derailment with its attendant loss of life and property. The service conditions of railway vehicles have become severe in recent years due to a general increase in operating speeds. Therefore, more precise evaluation of wheelset strength and safety has been desired. Damages of railway wheel are a spatting by wheel/rail contact and thermal crack by braking heat etc. One of the main source of damage is a residual stress. therefore it is important to evaluate exactly. A Residual stress of wheel is formed at the process of heat treatment when manufacturing. it is changed by contact stress developed by wheel/rail contact and thermal stress from heat induced in braking. The objective of this paper is to estimate the variation and magnitude of the residual stress of railway wheel.

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Critical Speed Analysis of Geogrid-Reinforced Rail Roadbed (지오그리드로 보강된 철도노반의 한계속도에 관한 연구)

  • 신은철;이규진;오영인
    • Proceedings of the KSR Conference
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    • pp.534-539
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    • 2001
  • This paper presents the critical speed analysis of geogrid-reinforced rail roadbeds on soft soil. A rail roadbed on soft ground must be designed to avoid intolerable stress in the underlying soil and to give sufficient support for the rail system. At high speeds, the deformation of rail systems will gain dynamic amplification, and reach excessive values as a certain speed, here termed critical speed is approached. The elastic Winkler foundation model was used to predict the critical speed of geogrid-reinforced rail roadbeds on soft soil and the model properties were determined by the in-situ cyclic plate load test. Based on the parametric study of elastic beam on Winkler foundation model, the critical speed increase with the increase of the flexural risidity of subgrade EI and the stiffness coefficient of Winkler foundation k. From the in-situ cyclic load tests and analysis of elastic beam on Winkler foundation model, the critical speed increase with increase in number of reinforced layer and non-dimensional value for depth of first geogrid layers and the thickness of reinforced rail roadbed u/d.

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A Study on Fatigue Crack Propagation of Rail Steel under Constant and Mixed Mode Variable Amplitude Loadings

  • Kim, Chul-Su;Chung, Kwang-Woo
    • International Journal of Railway
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    • v.5 no.2
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    • pp.71-76
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    • 2012
  • Recently, axle load, operating speed and traffic density on railroads have had a tendency to increase and thereby cause additional pressure applied on used track. These operating conditions frequently result in service failure due to wear caused by wheel-rail contact and fatigue damage under cyclic loading. Among rail defects, the transverse crack, which has been the most dangerous type of fatigue damages, is developed from the subsurface crack near the rail running face and grows perpendicular to the rail surface. Therefore, it is necessary to investigate systematically the growth behavior of transverse crack for rail steel under mixed mode. In this study, the fatigue crack growth behavior of the transverse crack in rail steel was experimentally investigated under mixed-mode variable amplitude loadings.

Safely Evaluation on Common Grounding System for Electric Railway (전기철도의 공용접지 시스템에 대한 안정성 평가에 관한 연구)

  • Song, Jin-Ho;Hwang, Yu-Mo
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.51 no.6
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    • pp.298-306
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    • 2002
  • We performed an safety evaluation on constructing of a common grounding system for electrical railway in view of its efficacy and technical fit. In order to compare the conventional grounding method, which has been individually conducted, with the common grounding with all ground wires connected in common to the counterpoise buried below the surface of the earth in parallel with rail, we set up scenarios with several cases of fault and load conditions in Chungbuk railway sections with the common grounding system. Based on models for railway conductors including the grounded system, line Parameters of railway power system are computed. The circuit model for power system with up and down lines, auto-transformers and railway substations is used to compute impedances of counterpoise and substation ground net. For each scenario with faults and operation conditions of railway, the induced potentials on signal and communication lines are also computed. It is shown that the common grounding for Chungbuk railway is superior experimentally to the conventional method in three respects: (1) the lower rail potentials during operation of railway in line, (2) the lower rail potentials for short-circuit faults between catenary and rail, and (3) the lower stress voltages on signal and communication lines for short-circuit or ground faults. The analysis results confirm that the grounding system for electric railway is required to be built by the common grounding and be evaluated on its safety in design.

Continuous deformation measurement for track based on distributed optical fiber sensor

  • He, Jianping;Li, Peigang;Zhang, Shihai
    • Structural Monitoring and Maintenance
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    • v.7 no.1
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    • pp.1-12
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    • 2020
  • Railway tracks are the direct supporting structures of the trains, which are vulnerable to produce large deformation under the temperature stress or subgrade settlement. The health status of track is critical, and the track should be routinely monitored to improve safety, lower the risk of excess deformation and provide reliable maintenance strategy. In this paper, the distributed optical fiber sensor was proposed to monitor the continuous deformation of the track. In order to validate the feasibility of the monitoring method, two deformation monitoring tests on one steel rail model in laboratory and on one real railway tack in outdoor were conducted respectively. In the model test, the working conditions of simply supported beam and continuous beam in the rail model under several concentrated loads were set to simulate different stress conditions of the real rail, respectively. In order to evaluate the monitoring accuracy, one distributed optical fiber sensor and one fiber Bragg grating (FBG) sensor were installed on the lower surface of the rail model, the strain measured by FBG sensor and the strain calculated from FEA were taken as measurement references. The model test results show that the strain measured by distributed optical fiber sensor has a good agreement with those measured by FBG sensor and FEA. In the outdoor test, the real track suffered from displacement and temperature loads. The distributed optical fiber sensor installed on the rail can monitor the corresponding strain and temperature with a good accuracy.