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서정원,허현무,최재붕,김영진,Seo Jung-Won,Hur Hun-Mu,Choi Jae-Boong,Kim Young-Jin 대한기계학회 2005 大韓機械學會論文集A Vol.29 No.10
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.
서정원(Seo Jung-Won),허현무(Hu Hun-Mu),이동형(Lee Dong-Hyeong),정흥채(Chung Heung-Chai) 한국철도학회 2004 한국철도학회 학술발표대회논문집 Vol.- No.-
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. One of the major reasons of railway wheel damage is a contact zone failure by wheel/rail contact. In this paper, we conducted a rolling contact fatigue test for wheels using a specimen of wheel/rail. the behavior of hardeness and residual stress below the contact surface of the test pieces in the fatigue process were analyzed. Finally, the relation between fatigue life and contact pressure was obtained.
서정원(Jung-won Seo),구병춘(Byenug-Choon Goo),정흥채(Heung-Chai Chung) 한국철도학회 2003 철도저널 Vol.6 No.2
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.
서정원(Seo Jung-Won),전현규(Jun Hyun-Kyu),김재철(Kim Jae-cheol),김대상(Kim Dae-sang) 한국철도학회 2009 한국철도학회 학술발표대회논문집 Vol.2009 No.11월
Rolling contact fatigue damages on the surface of rail such as head check, squats are one of growing problems. Since rail fracture can cause derailment with loss of life and property, the understanding of rail fracture mechanisms is important for reducing damages on the surface of rail. In this study, the fatigue crack at the upper surface of rail was investigated by means of failure analysis. The investigation indicate that the crack grows at about 70° to the surface of the rail and this crack changed its growth direction ; either to branch downwards at about 20° or to branch upwards. Since the downward branches lead to fracture of the rail, they are more dangerous to the integrity of rails. It has been observed that White Etching Layer(WEL) occurs within the surface of broken rail. It was found that the fatigue crack initiation and propagation was accelerated by the WEL.