• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.695-699
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• 2010

The propellant KM10, a single propellant manufactured from nitrocellulose, was known to cause natural degradation phenomena at long term storage. In this study, the self-life was estimated using high temperature acceleration aging tests and stockpile analysis test. For the life expectancy estimation, Arrhenius equation and Berthelot equation were used in the high temperature acceleration tests, and the first order regression was used in the Stockpile analysis test. The self-life of propellant KM10 using the Arrhenius equation and Berthelot equation showed significantly different results as 43.73, 16.53 years in the high temperature acceleration test, and it showed 42.94 years in the Stockpile analysis test. The value of self-life predicted by Arrhenius equation was reasonable when compared with the result of E. R. Bixon.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.751-757
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• 2012

An accelerated life test (ALT) is a test method that forces components to fail more quickly than they would under use conditions by applying higher overstresses. When two or more accelerating stresses are involved in an ALT, an interaction effect may occur. In previous studies, mostly ALTs without considering an interaction of accelerated stresses and accelerated life models were proposed. The life data obtained are extrapolated using a life-stress relationship to estimate the life distribution at use conditions. We use the general log-linear relationship to model the dependence of life in the Weibull distribution on stress. Therefore, this study suggests the acceleration factor model between the lives at use conditions and accelerated conditions by using mechanical component life data considering an interaction effect. Further, the accelerated life test method and acceleration factor model proposed in this paper will be the basis for adopting an accelerated life test with accelerated stress interactions.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.3
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• pp.69-78
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• 2010

Korea Aerospace Research Institute started on design and development of a hypersonic air-breathing engine test facility from 2000 and completed the test facility installation in July 2009. This facility, designated as Scramjet engine test facility(SeTF), is a blow-down type high enthalpy wind tunnel which has a pressurized air supply system, air heater system, free-jet test chamber, fuel supply system, facility control/measurement system and exhaust system. In this paper, details of the specifications, and configuration of the SeTF are described. For verifying characteristics of the SeTF, wind tunnel tests are now on progress and some of the data are also described.

• Journal of the Korean Geotechnical Society
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• v.21 no.9
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• pp.65-75
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• 2005

Maximum shear modulus of soil is a principal parameter for the design of earth structures under static and dynamic loads. In this study, the statistical data of maximum shear moduli of silty sands in Songdo area in the west coast of Korea evaluated by various field and laboratory tests - standard penetration test (SPT), cone penetration test (CPT), self-boring pressuremeter test (SBPT), downhole test (DH), seismic cone penetration test (SCPT) and resonant column test (RC) were analyzed. Based on the measurement of shear moduli using DH which is known as maximum value at very small strain, the new empirical correlations between shear moduli and SPT or CPT values were proposed. Predictions of maximum shear moduli using the proposed correlations were compared with the data obtained from DH. The good agreement confirmed that the proposed correlations reasonably predicted the maximum shear moduli of silty sands in the area.

• Journal of the Korean Society for Railway
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• v.17 no.2
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• pp.114-122
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• 2014

An asphalt trackbed is to be adapted in Korea to provide better bearing capacity and stability to the track and a comfortable ride to passengers. The dynamic modulus of Hot Mixed Asphalt(HMA) mixes is a critical design input parameter to determine the thickness of the asphalt trackbed. In this study, impact resonant tests and ultrasonic test methods are designed to obtain the dynamic modulus. These test methods are also verified to check the etffectiveness of constructing a master curve of the dynamic modulus over a wide range of frequencies and temperatures. The test results are compared to the computed dynamic modulus using AASHTO 2002 and the KPRP's proposed model. It can be concluded that the proposed simple test methods are effective to obtain the dynamic moduli of the asphalt mixes for the design of an asphalt trackbed foundation.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.94-102
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• 2011

Sub-system requirements of a pressure-fed hot-firing test facility for performance assessment of a Liquid Rocket Engine(LRE) thrust chamber using Liquid oxygen and kerosene were described. These requirements were based on the experience of construction and operation of the ground hot-firing test facility which was used for the development of the KSR-III and a 30 tonf-class LRE thrust chamber. So it is expected that this paper is used as a basic material and an itemized previous review statement for the design and construction of a large hot-firing test facility.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.63-71
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• 2010

Sub-system requirements of a pressure-fed hot-firing test facility for performance assessment of a Liquid Rocket Engine(LRE) thrust chamber using Liquid oxygen and kerosene were described. These requirements were based on the experience of construction and operation of the ground hot-firing test facility which was used for the development of the KSR-III and a 30 $ton_f$-class LRE thrust chamber. So it is expected that this paper is used as a basic material and an itemized previous review statement for the design and construction of a large hot-firing test facility.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.277-287
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• 2009

The objective of this study was to experimentally investigate the structural behavior of steel plate concrete walls with vertical ribs (SSC walls), to compare the experimental results with the currently applied evaluation equations, and to obtain information that would be useful in the development of design equations for SSC walls. SSC test specimens that were subjected to in plane shear forces and bending moments were fabricated and tested. The experimental results show that the effect of vertical ribs on the structural behavior of SSC walls may be neglected, and that the confinement effect of concrete on the steel plates on both sides of the walls was negligible. The comparison of the experimental results with the evaluation equations showed that the structural behavior of SSC walls under shear control is close to that of the evaluation equations, but that the behavior of SSC walls under larger bending moments is not very close to that of the evaluation equations. The current evaluation equations for USC walls may be applied to the design of SSC walls because the structural walls of nuclear power plants are not subjected to large in plane bending moments.

• Tunnel and Underground Space
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• v.18 no.4
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• pp.252-262
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• 2008

In the uniaxial compressive test of a single specimen of transversely isotropic rock, its 5 independent elastic constants can not be defined since maximum 4 independent strain measurements are available theoretically. In order to solve this problem, one equation proposed by Saint Venant in 19C and confirmed by Lekhnitskii through the test experiences has been used for long time. Accordign to authors' experiences, however, this equation turned out to give erroneous elastic constants in some cases. Three new equations are suggested and their compatibilities are discussed in this paper. As the results of the analyses of the models, Lekhnitskii's suggested equation is effective for the specimen with the high dip angle whereas it results in the large erred output for that with dip angle less than $25{\sim}30$. It was found that the effectivenesses of three suggested equations and their compatibilities are subject to the dip angle and not to the amounts of elastic constants. Guide map to the selection of the compatible one of those suggested equations is presented as a result of the study.

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.225-230
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• 1999

Ball-on-3-ball 시험에서 이축 강도를 결정하기 위한 방법에 대해 고찰하였다. 알루미나 시편을 이용하여 ball-on-3-ball 시험과 poston-on-3-ball 시험을 하여 이축 강도를 측정하였다. piston-on-3-ball 시험에서의 강도 식과 등가 반지름을 이용하여 계산한 ball-on-3-ball 시험에서의 이축 강도와, piston-on-3-ball 시험에서의 이축 강도를 분산 분석(ANOVA)한 결과, 두 평균이 동일하다고 할 수 있었다. 따라서, ball-on-3-ball 시험에서의 이축 강도는 piston-on-3-ball 시험에서의 강도 식과 등가 반지름을 이용하여 계산할 수 있다. 또한, 유한 요소법을 이용하여 ball-on-3-ball 시험시 시편에 인가되는 응력 분포를 고찰해 보았다.