• Proceedings of the KSR Conference
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• 2007.11a
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• pp.278-282
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• 2007

The riding comfort and the durability of train are effected by the rail irregularities such as track gauge, superelevation, alignment, longitudinal level, twist, cant and cross level. Inspection and estimation of irregularities are very important to maintain the rail condition. Generally, the EM120 has been utilized to measure the rail irregularities once a month in Korea. However, the EM120 can be operated at night time only, because the inspection speed of EM120 is much slower than the speed of high-speed trains. Also, the EM120 is too slow to inspect effectively for the whole commercial line. Therefore, we have mounted the track inspection system on the High-Speed Rolling Stock 350 eXperimental (HSR350X) and measured the rail irregularities to confirm the condition of a rail while running 300km/h. In this paper, the track inspection system mounted on HSR350X is mainly considered, and the measured results through test run are introduced.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.139-145
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• 1996

Tapping is one of the most widely used machining operations. There are several methodes of producing external screw threads, e.g. turning, milling with single or multiple cutter, rolling, and grinding, but the methods available for cutting enternal threads are less numerous, and for threads in small holes, tapping is employed almost exclusively. In this study, the tap with the various geometry has been developed in order to tap special workmaterial at considerably higher cutting speed than that of the conventional HSS tap. The experimental tests are run with various cutting speed by using a piezo type tool dynamometer to measure tapping torque. Tapping torque is affected by the design of the tap, which seems to be due to internal friction and shearing of the metal. It is clarified that the process of chip formation strongly depends on rake angle, relief angle, angle of twist.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1270-1276
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• 2003

This paper describes an analytical method for wheel wear prediction. The outputs from vehicle dynamic software are used to calculation the wheel wear. Two calculation examples are shown for a high-speed line and a conventional line. Through the comparison of two cases, we can see the wheel wear characteristics on the conventional line and the high-speed line. The conventional line has many curved tracks that cause severe wheel flange wear. The influences of curve radius on wheel wear are also described considering the operational performance of the high speed trainset. A method of calculation using contact patch work model is presented for determination of the evolution by wear railway wheels.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1995.03a
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• pp.9-16
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• 1995

The thermal deformation of machine tool spindle influences the performance of the manufacturing systems for precision products. In this research thermal analysis of a high speed machine tool spindle with the rolling bearing and the built-in motor is carried out using Finite Difference Method. The thermal boundary conditions describing the hear generation in the bearing and built-in motor are considered in the simulation. And various convective boundary conditions are assumed with the empirical formula in the references. From the simulation results the characteristics of each element affecting the dynamic thermal behaviour of the machine tool spindle systems have been clarified. This model can be well applied to the future development of the high speed spindle systems.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.4
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• pp.90-97
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• 1996

The thermal deformation of a machine tool spindle influences the performance of the manufacturing systems for precision products. In this research, thermal analysis of a high speed machine tool spindle with the rolling bearing and the built-in motor is carried out by using Finite Difference Method. The thermal boundary conditions describing the heat generation in the bearing and built-in motor are considered in the simulation. And various convective boundary conditions are assumed with the empirical formula in the references. From the simulation results, the characteristics of each element affecting the dynamic thermal behaviour of the machine tool spindle system have been clarified. Therefore, this model can be well applied to the future development of the high speed spindle systems.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.360-363
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• 2007

This paper deals with the dynamic tensile characteristics of the steel sheets for structural members of a train. Train accidents occurs rarely but lead to many casualties and economical loss. Therefore the safety of the train becomes important during the train crash. The dynamic tensile characteristics of the steel sheets are indispensable to analyze the structural crashworthiness. Current research reports the stress-strain curves, fracture elongation and strain rate sensitivities evaluated at the various strain rates especially for SUS304L-ST and SUS304L-LT steel sheets. The results include the difference in the dynamic tensile characteristics of both rolling and transverse directions. Dynamic tensile tests were performed at the strain rates ranging from 0.003/sec to 200/sec using High Speed Material Testing Machine. The materials tested in this research shows interesting behavior at the low strain rates. The strain hardening exponent decreases remarkably while the yield strength increases.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.104-111
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• 2011

An ultrafine grained Mg-9Al-1Zn magnesium alloy with the mean grain size less than $1{\mu}m$ was produced by using high-ratio differential speed rolling. The processed alloy exhibited excellent superplasticity at relatively low temperatures. The micro-forming tests were carried out using a micro-forging apparatus with micro V-grooved shaped dies made of silicon and the micro-formability was evaluated by means of micro-formability index, $R_f$ ($=A_f/A_g$, $A_f$: formed and inflowed area into the V-groove, $A_g$: area of the V-groove). The $R_f$ value increased with temperature up to $280^{\circ}C$ and then decreased beyond $300^{\circ}C$. The decrease of the $R_f$ value at $300^{\circ}C$ was attributed to the accelerated grain coarsening. Increasing the micro-forging pressure increased the $R_f$ values. At a given die geometry, die filling ability decreased as the die position moved away from the die center to the end. FEM simulation predicted this behavior and a method of improving this problem was proposed.

• International Journal of Advanced Culture Technology
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• v.10 no.4
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• pp.569-575
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• 2022

This is a research thesis on the development of a monitoring and diagnosis device that prevents the risk of an accident through monitoring and diagnosis of a modular Main Circuit Breaker (MCB) using Vacuum Interrupter (VI) for Korean high-speed rolling stock. In this paper, a comprehensive MCB monitoring and diagnosis was performed by converging vacuum level diagnosis of interrupter, operating coil monitoring of MCB and environmental temperature/humidity monitoring of modular box. In addition, to develop an algorithm that is expected to have a similar data processing before the actual field test of the MCB monitoring and diagnosis device in 2023, the cluster analysis and factor analysis were performed using the WEKA data mining technique on the big data of Korean railroad transformer, which was previously researched by Tae Hee Evolution with KORAIL.

• Tribology and Lubricants
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• v.37 no.1
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• pp.7-13
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• 2021

Ball bearing is a device that supports and transmits a load acting on a rotating shaft, and it is a type of rolling bearings that uses the rolling friction of the balls by inserting balls between the inner ring and the outer ring. Grease, which is prepared by mixing a thickener with a base oil, is a lubricant commonly used in bearings and has the advantage of a simple structure and easy handling. Bearings are increasingly being used in high value-added products such as semiconductors, aviation, and robots in the era of the 4th industrial revolution. Accordingly, there is an increasing demand for bearing grease. The selection of grease is an important factor in the bearing design. Therefore, a study must be conducted on the grease life evaluation to select an appropriate grease according to operating conditions such as a high temperature, high rotational speed, and high load. In this study, we evaluate the life of ball-bearing grease according to various operating conditions, namely, temperature, speed, and load changes. For this, we develop and theoretically verify a grease life test machine for ball bearings. We conduct a life test of grease according to various operating conditions of bearings and predict the grease life with a 10% and 50% failure probability using the Weibull analysis. In addition, we analyze the oxide characteristics of the grease over time using the Fourier transform infrared spectroscopy and the deterioration characteristics of the grease using the carbonyl index.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.2
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• pp.206-211
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• 2010

Since high-speed train is a dynamic load in which electric power is externally supplied, contact loss between the catenary and pantograph occurs. This phenomena including vibrations generates frequently irregular arcs, which, in turn causes EMI. Thus it is very important to develop the approach to reduce arc phenomenon by contact loss, as speed of electric railway vehicle increases. In case of an electric railway vehicle using electrical power, compared with diesel rolling stock, Power Line Disturbance(PLD) such as harmonics, transient voltage and current, Electromagnetic Interference(EMI), and dummy signal injection etc usually occur. In this study, the dynamic characteristics of a contact wire and a pantograph suppling electrical power to high-speed train are investigated with an electrical response point. To implement power line disturbance induced by contact loss phenomenon for high speed train operation, a hardware simulator which considers contact loss between contact wire and pantograph as well as contact wire deviation is developed. It is confirmed by the experiments that contact loss effect is largely dependent on voltage conditions when the contact loss occurs. Also, a passive filter is designed to reduce power disturbance and the designed system is verified by experiment.