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Wear and Chattering Characteristics of Rail Materials by Ultrasonic Nanocrystal Surface Modification
Chang, Seky,Pyun, Young-sik,Amanov, Auezhan Korean Society for Precision Engineering 2015 International Journal of Precision Engineering and Vol.16 No.11
Stick-slip wear, sliding wear, rolling contact wear, fatigue failure and chattering are persistent problems of a wheel-rail interface, especially at corner track. Generally, high strength alloy and heat-treated rail were used at corner track in order to improve the service life and chattering level, but these targets still remain as unceasing challenge subject. Ultrasonic nanocrystal surface modification (UNSM) was applied to rail materials with the aim of replacing with heat treatment and/or improving the service life of rails. In this study, the mechanical and wear properties of the untreated and UNSM-treated specimens which were prepared from normal and heat treated rails. Friction and wear tests were performed to measure the friction coefficient and the amount of wear. Results revealed that the wear performance of the UNSM-treated specimens was improved due to the increased hardness and induced compressive residual stress after UNSM treatment. The wear mechanism of the UNSM-treated specimens was explained with the changes in surface properties of rail materials.
장세기(Chang Seky),신민호(Shin Min-Ho) 한국철도학회 2002 한국철도학회 학술발표대회논문집 Vol.- No.-
Railroad has been one of major public transportations with the advantages of safety and schedule accuracy. However, the sustainable development will be the first principle in order to save the earth environment in the future, and the only transportation that satisfies it can continuously survive. Transportation has caused air pollution severely. Thus, the most environment-friendly means of transport should be chosen to maintain clean environment in the 21st century. Railroad is currently the best choice to fulfill the mission. But, the overall railroad technologies should be developed in consideration of clean environment to be a future leading transportation.
장세기(Seky Chang),김용기(Yong Ki Kim),오창록(Chang-Rok Oh),구병춘(Byeong-Choon Goo) 한국철도학회 2004 한국철도학회 학술발표대회논문집 Vol.- No.-
Underframes of rolling stock structure are made of hot rolled steel of SS400 or SM490A. While these underframe steels are designed to satisfy the mechanical requirements, theircorrosion behavior also should taken into account. Underframes are coated to prevent corrosion, but they are often defected by external factors to result in local corrosion which may cause the weakness of mechanical strength. Thus, the corrosion of underframe steels was examined through atmospheric corrosion test to estimate service life and safety.
장세기(Seky Chang),편영식(Young-Sik Pyun) 한국생산제조학회 2016 한국생산제조학회지 Vol.25 No.5
Railway tracks are repeatedly overstressed and damaged owing to increase in passing tonnage and numerous contact cycles between wheels of train and rails. In order to ensure safe train operation, heat-treated rails are used in addition to regular inspection and maintenance of these rails. Normal rails were treated using ultrasonic nanocrystal surface modification (UNSM) to strengthen the surface of rails. A few changes in surface properties were detected with respect to hardness and compressive residual stress after UNSM treatment. Wear and rolling contact fatigue tests were performed using rails whose surfaces were hardened by UNSM and heat-treated rails. The amount of wear and fatigue life cycles were measured to estimate the effect of UNSM on the rail material. The material of the surface-hardened rail showed improved wear and rolling contact fatigue properties.
장세기(Seky Chang),김용기(Yong-Ki Kim),구병춘(Byeong-Choon Goo) 한국철도학회 2002 한국철도학회 학술발표대회논문집 Vol.- No.-
Rail cars are subject to vibration, impact and wear which can cause severe defects leading to a fatal accident Thus, they are designed and manufactured in consideration of such factors influencing their service lifetime. Under-frames are composed of steel and support most of load imposed on the car. Steel is very sensitive to corrosive environment and corroded even in a normal service condition. Regular maintenance can protect steel parts from corrosion by painting. However, an exposure of defect point to corrosive agents can make corrosion proceed to a considerable depth, which may cause the structure to remain under safety standard. It is necessary to understand corrosion behavior of rail cars in order to estimate unexpected accidents by corrosion.
장세기(Seky Chang),목재균(Jai Kyun Mok),임태훈(Lim Tae Hoon) 한국철도학회 2005 한국철도학회 학술발표대회논문집 Vol.- No.-
Power of fuel cell tram is supplied by only fuel cell system or hybrid system of fuel cell and battery/super capacity. Fuel cell is operated by hydrogen, which is fed directly from hydrogen tank or by reforming gasoline or methanol into hydrogen. Power system is preferred with hybrid of fuel cell and battery/super capacity since it improves total energy efficiency through interaction of hybrid components and restores energy regenerated by braking. Also, power supply system by fuel cell hybrid should be designed to output optimum energy efficiency depending on driving mode of fuel cell tram.