• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.4 s.235
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• pp.600-605
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• 2005

In this study, the ring tensile test at high temperature was suggested to evaluate the hoop tensile properties of small tube such as the cladding in the nuclear reactor Using the Arsene's ring model, the ring tensile test was performed and the test data were calibrated. From the result of the ring test with strain gauge and the numerical analysis with 1/8 model, LCRR(load-displacement conversion relationship of ring specimen) was determined. We could obtain the hoop tensile properties by means of applying the LCRR to the calibrated data of the ring tensile test. A few difference was observed in view of the shape of fractured surface and the fracture mechanism between at the high temperature and at the room temperature.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.947-953
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• 2010

The KTX-Sancheon has been commercially operating on the high-speed line since March. 2. In order to verify the performance of high-speed train and core equipments such as current collection system, sophisticated tests and evaluating procedures should have been considering. In this paper, the load cell with a built-in strain-gauge which developed to improve measuring method of contact force between the pantograph and catenary system is introduced. The static test results of the load cell shows that its design is very suitable and applicable for the dynamic test and on-line test. After the test and evaluation of load cell's dynamic calibration with pantograph, we will be applied to test interaction characteristics between the pantograph and catenary system on the high-speed line.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.177-180
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• 2007

The laser welding process was effective way to join the metals, because of the high productivity, the low distortion and the good weld quality. The fiber laser used the double-clad fiber architecture, the single element diode laser and the fully-spliced side pumping. It has the advantages in the views of the energy conversion efficiency, the beam quality, the robustness and the mobility. Recently, the thick material was welded with the high power laser in ship building or construction industry owing to the super bright fiber laser. In this study, we introduced the characteristics of high power fiber laser and its welding performance of thick gauge materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.456-459
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• 2002

This paper describes fabrication and characteristics of ceramic pressure sensor for working at high temperature. The proposed pressure sensor consists of a Ta-N thin-film, patterned on a Wheatstone bridge configuration, sputter deposited onto thermally oxidized Si membranes with an aluminium interconnection layer. The fabricated pressure sensor presents a low temperature coefficient of resistance, high sensitivity, low non-linearity and excellent temperature stability. The sensitivity is 1.097~1.21mV/$V{\cdot}kgf/cm^2$ in the temperature range of $25{\sim}200^{\circ}C$ and the maximum non-linearity is 0.43 %FS.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.138-143
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• 2006

Oscillatory wheel load fluctuation of considerable amplitude is almost always observed on railway vehicle running at high speed. From the acceleration measured on the axle-box, the frequency of this fluctuation is estimated to be approximately within 70 Hz. By the conventional measuring method, continuous outputs of wheel load can not be obtained, so it is difficult to investigate such a high frequency phenomenon exactly. We have developed a new method of measuring the forces and derailment coefficient continuously, using two pairs of strain gauge bridges whose output phases are shifted by 90 degree, and summing up the outputs with a weighting function. This method is available for measuring the forces between wheel and rail up to high frequency. In this paper, continuous method of measuring forces between wheel and rail and derailment coefficient.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.1
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• pp.1-4
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• 2003

This paper presents an attempt to develop probabilistic multistress life models to evaluate the lifetime characteristics of epoxy-encapsulated magnet wire with heavy build polyurethane enamel. A set of accelerated life tests were conducted over a wide range of pulsating voltages, temperatures, and frequencies. Samples of fine gauge twisted pairs of the encapsulated magnet wire were tested us-ing a pulse endurance dielectric test system. An electrical-thermal lifetime function was combined with the Weibull distribution of lifetimes. The parameters of the combined Weibull-electrical-thermal model were estimated using maximum likelihood estimation. Likewise, a generalized electrical-thermal-frequency life model was also developed. The parameters of this new model were estimated using multiple linear regression technique. It was found in this paper that lifetime estimates of the two proposed probabilistic multistress life models are good enough. This suggests the suitability of using the general electrical-thermal-frequency model to estimate the lifetime of the encapsulated magnet wire over a wide range of voltages, temperatures and pulsating frequencies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.192-196
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• 2002

This paper describes on the fabrication and characteristics of a metal thin-film pressure sensor based on Cr strain-gauges for harsh environment applications. The Cr thin-film strain-gauges are sputter-deposited onto a micromachined Si diaphragms with buried cavity for overpressure protectors. The proposed device takes advantages of the good mechanical properties of single-crystalline Si as diaphragms fabricated by SDB and electrochemical etch-stop technology, and in order to extend the operating temperature range, it incorporates relatively the high resistance, stability and gauge factor of Cr thin-films. The fabricated pressure sensor presents a low temperature coefficient of resistance, high-sensitivity, low non-linearity and excellent temperature stability. The sensitivity is 1.097~1.21 $mV/V{\cdot}kgf/cm^2$ in the temperature range of $25{\sim}200^{\circ}C$ and the maximum non-linearity is 0.43 %FS.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.999-1006
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• 2004

Recently, the ride comfort problem becomes increasingly important because of today's needs for train speedup. The railway has the track irregularities which cause vibrations, such as rail joints, turnout, level crossing, transition corves and super-elevation ramps, and variations in the track level(z-axis) and the gauge(y-axis). In Korea, the service run of the high speed train has been made since the 1st of April, 2004. The commercial high-speed trains must be run on the compound lines which are composed of high-speed line and conventional line. The high speed lines in both Kyoungbu line and Honam line have 57.5％ and 33.8％, respectively In this Paper, the ride comfort has been reviewed by the various experimental methods when the high-speed trains are operated on both Kyoungbu line and Honam line. The results show that the high-speed train has no problems from the viewpoint of the comfort ride during the operation on the high speed line and conventional line.

• Journal of the Korean Wood Science and Technology
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• v.26 no.4
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• pp.1-5
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• 1998

In this study, it was examined the method to estimate equilibrium moisture content(EMC) at high vapor pressures and high temperatures above $100^{\circ}C$. The material used for the experiment was Sugi(Cryptomeria japonica). EMC was investigated at temperatures ranging from $100^{\circ}C$ to $160^{\circ}C$ and under saturated vapor pressures above 1 atm. The correlation between temperatures and vapor pressures have a good agreement with those observed by thermocouple and pressure gauge in the air state of autoclave, respectively. A sensitivity of quartz spring was 65mm/g. Moisture content(MC)s calculated from the quartz spring elongation by vapor sorption showed a good agreement with MCs by oven-dried method. Using this system, it was found that EMC at high vapor pressures and high temperatures above $100^{\circ}C$ were higher than EMC of wood in 1 atm pressure conditions. With this system, therefore, it was concluded that the EMCs of wood and wood-based materials at high temperatures were able to be evaluated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.11a
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• pp.85-88
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• 2008

As super-high-strength concrete uses a large amount of binder, there is an autogenous shrinkage strain larger than dry shrinkage and it degrades the quality of structures. Thus, we need a technology to minimize the shrinkage strain of super-high-strength concrete. Accordingly, the present study prepared super-high-strength concrete with design strength of over 100MPa and, using an embedded gauge, measured the shrinkage strain of free shrinkage specimens for super-high-strength concrete containing expansion agent. According to the results of this study, the expansion rate of concrete increased in the early stage due to the admixture of expansion agent, but the shrinkage rate went down with the lapse of time. The effect of the admixture of expansion agent on compressive strength appeared insignificant. Further research shall be made on different kinds of expansion agents and various mixture ratios for basic analysis to reduce autogenous shrinkage of super-high-strength concrete.