• Title/Summary/Keyword: Railway wheel

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Safety Margin Evaluation of Railway wheel Based on Fracture Scenarios

  • Kwon, Seok Jin;Lee, Dong Hyung;Seo, Jung Won;Kwon, Sung Tae
    • International Journal of Railway
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    • v.5 no.2
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    • pp.84-88
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    • 2012
  • Derailment due to wheel failure would cause a tremendous social and economical cost in service operation. It is necessary to evaluate quantitatively the safety with respect to high-speed train. Although the safety of railway wheel has been ensured by an regular inspection, all critical defects cannot be detected in inspection cycles and the wheel has been replaced because a defect quickly become critical for safety. Therefore, it is important to calculate quantitatively the fracture limit and remnant life of damaged railway wheel in wheel-rail system. In present paper, the critical crack size of wheel for high-speed train is simulated based on fracture scenario and the safety of wheel is evaluated.

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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Effect of Metal Removal and Initial Residual Stress on Contact Fatigue Life (초기 잔류응력과 접촉표면 제거가 접촉피로수명에 미치는 영향)

  • Hur Hun-Mu;Goo Byeong-Choon;Choi Jae-Boong;Kim Young-Jin;Seo Jung-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.2
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    • pp.341-349
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    • 2005
  • Damage often occurs on the surface of railway wheel by wheel-rail contact fatigue. It should be removed before reaching wheel failure, because wheel failure can cause derailment with loss of life and property. The increase or decrease of the contact fatigue life by the metal removal of the contact surface were shown by many researchers, but it has not explained precisely why fatigue life increases or decreases. In this study, the effect of metal removal depth on the contact fatigue life for railway wheel has been evaluated by applying finite element analysis. It has been revealed that the residual stress and the plastic flow are the main factors determining the fatigue life. The railway wheel has the initial residual stress formed during the manufacturing process, and the residual stress is changed by thermal stress induced by braking. It has been found that the initial residual stress determines the amount of metal removal depth. Also, the effects of the initial residual stress and metal removal on the contact fatigue lift has been estimated, and an equation is proposed to decide the optimal metal removal depth for maximizing the contact fatigue life.

Damage Evaluation of Wheel Tread for High Speed Train Using Replication and Fracture Mechanics Characteristics (비파괴적 표면조직검사법과 파괴역학 특성에 따른 고속철도용 차륜 답면의 손상 평가)

  • Kwon, Seok-Jin;Lee, Dong-Hyung;Seo, Jung-Won;Kwon, Sung-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.7
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    • pp.756-763
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    • 2007
  • The majority of catastrophic wheel failures are caused by surface opening fatigue cracks either in the wheel tread or wheel flange areas. The inclined cracks at railway wheel tread are initiated and the cracks are caused by wheel damage-spatting after 60,000 km running. Because the failured railway wheel is reprofiled before regular wheel reprofiling, the maintenance cost for the railway wheel is increased. Therefore, it is necessary to analyze the mechanism for initiation of crack. In the present paper, the combined effect on railway wheels of a periodically varying contact pressure and an intermittent thermal braking loading is investigated. To analyze damage cause for railway wheels, the measurements for replication of wheel surface and the effect of braking application in field test are carried out. The result shows that the damages in railway wheel tread are due to combination of thermal loading and ratcheting.

Evaluation of Surface and Sub-surface defects in Railway Wheel Using Induced Current Focused Potential Drops (집중유도 교류 전위차법을 이용한 철도차량 차륜의 표면과 내부 결함 평가)

  • Lee, Dong-Hyung;Kwon, Seok-Jin
    • Journal of the Korean Society for Railway
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    • v.10 no.1
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    • pp.1-6
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    • 2007
  • Railway wheels in service are regularly checked by ultrasonic testing, acoustic emission and eddy current testing method and so on. However, ultrasonic testing is sometimes inadequate for sensitively detecting the cracks in railway wheel which is mainly because of the fact of crack closure. Recently, many researchers have actively fried to improve precision for defect detection of railway wheel. The development of a nondestructive measurement tool for wheel defects and its use for the maintenance of railway wheels would be useful to prevent wheel failure. The induced current focusing potential drop(ICFPD) technique is a new non-destructive tasting technique that can detect defects in railway wheels by applying on electro-magnetic field and potential drops variation. In the present paper, the ICFPD technique is applied to the detection of surface and internal defects for railway wheels. To defect the defects for railway wheels, the sensor for ICFPD is optimized and the tests are carried out with respect to 4 surface defects and 6 internal defects each other. The results show that the surface crack depth of 0.5 mm and internal crack depth of 0.7 mm in wheel tread could be detected by using this method. The ICFPB method is useful to detect the defect that initiated in the tread of railway wheels

Evaluation of Multiaxial Fatigue Strength of a Urban Railway Wheel Steel (도시철도 차량 차륜재의 다축 피로강도 평가)

  • Ahn, Jong-Gon;You, In-Dong;Kwon, Seok-Jin;Kim, Ho-Kyung
    • Journal of the Korean Society of Safety
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    • v.27 no.2
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    • pp.1-6
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    • 2012
  • Uniaxial and biaxial torsional fatigue tests were conducted on the samples extracted from urban railway wheel steel. Ultimate and yield strengths of the steel were 1027.7 MPa and 626 MPa, respectively. The uniaxial fatigue limit was 422.5 MPa, corresponding 67% of the ultimate tensile strength. The ratio of ${\tau}_e/{\sigma}_e$ was 0.63. Fatigue strength coefficient and exponent were 1319.5 MPa and 0.339, respectively. Maximum principal and equivalent strain were found to be adequate parameter to predict fatigue lifetime of the steel under multiaixal fatigue condition.

Estimation of Contact Fatigue Initiation Lifetime of an Urban Railway Wheel (도시철도 차륜의 접촉피로 초기수명 평가)

  • Ahn, Jong-Gon;You, In-Dong;Kwon, Seok-Jin;Kim, Ho-Kyung
    • Tribology and Lubricants
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    • v.28 no.1
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    • pp.19-26
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    • 2012
  • Rolling contact fatigue of an urban railway wheel was analysed during its rolling. A FEM analysis was performed using a 3D modelling of rail and wheel, considering the slope of the rail and nonlinear isotropic and kinematic hardening behavior of the rail and the wheel. The maximum von-Mises stress and contact pressure between the rail and wheel were 656.9 MPa and 1111.4 MPa, respectively, under axial load of 85 kN with friction coefficient of 0. The fatigue initiation life prediction relationships by strain-lifetime (${\varepsilon}$-N) and Smith-Watson-Topper method were drawn for the wheel steel as follows: $N_i=7.35{\times}10^6{\times}SWT^{-3.56}$ and $N_i=5.41{\times}10^{-9}{\times}(\frac{{\Delta}{\varepsilon}}{2})^{-5.77}$. The fatigue lifetimes of the wheel due to rolling contact were determined to be infinite by ${\varepsilon}$-N and SWT methods.

Effect of Metal Removal and Traction Force on Contact Fatigue Life (견인력과 접촉표면 제거가 접촉피로수명에 미치는 영향)

  • Seo Jung-Won;Hur Hun-Mu;Choi Jae-Boong;Kim Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.10
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    • pp.1384-1391
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    • 2005
  • Damage often occurs on the surface of railway wheels due to wheel-rail contact fatigue. It should be removed before reaching wheel failure, because wheel failure can cause derailment with loss of life and property. The increase or decrease of the contact fatigue lift by the metal removal of the contact surface were investigated by many researchers, but they have not considered initial residual stress and traction force. The railway wheel has the initial residual stress formed during the manufacturing process, and the residual stress is changed by thermal stress induced by braking. The traction force and residual stress are operated on wheels of locomotive and electric motor vehicle. In this study, the effect of metal removal depth on the contact fatigue life for a railway wheel has been evaluated by applying lolling contact fatigue test. The effect of the traction force and metal removal on the contact fatigue life has been estimated by finite element analysis. It has been found that the initial residual stress determines the amount of metal removal depth if the traction coefficient is less than 0.15. If the traction coefficient is greater than 0.2, however, the amount of metal removal depth is independent on the intial residual stress.

A Study on the Contact Fatigue Life Evaluation for Railway Wheels Considering Residual Stress Variation (잔류응력 변화를 고려한 철도차량 차륜의 접촉피로 수명평가)

  • Seo, Jung-Won;Goo, Byeong-Choon;Choi, Jae-Boong;Kim, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.9
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    • pp.1391-1398
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    • 2004
  • Railway wheels and axles belong to the most critical components in railway vehicles. The service conditions of railway vehicles became more severe in recent years due to the increase of speed. Therefore, a more precise evaluation of wheelset life and safety has been requested. Wheel/rail contact fatigue and thermal cracks due to braking heat are two main mechanisms of the railway wheel failure. In this paper, an evaluation procedure for the contact fatigue life of railway wheel is proposed. One of the main sources of the contact zone failure is the residual stress. The residual stress on wheel is formed during the manufacturing process which includes a heat treatment, and then is changed by contact stress developed by wheel/rail contact and thermal stress induced by braking. Also, the cyclic stress history for fatigue analysis is determined by applying finite elements analysis for the moving contact load. The objective of this paper is to estimate fatigue life by considering residual stress due to heat treatment, braking and repeated contact load, respectively.