• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.8
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• pp.581-588
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• 2020

The aging characteristics of exploding foil initiator (EFI) are studied. In order to observe the aging characteristics, the main components of the exploding foil initiator were classified and the failure mechanism was defined. The aging characteristics were defined in terms of power and sensitivity, and the accelerated aging test plan was established based on the activation energy calculated by HFC (Heat Flow Calorimetry) and Arrhenius theory. The performance variation was observed using the sensitivity test (Neyer test) and power test (Dent test) for the aged samples. The aging characteristic was observed on the mean exploding point of the sensitivity test, but long-enough life span was predicted considering the related specification.

• Composites Research
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• v.22 no.3
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• pp.35-43
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• 2009

In this study, for a radiator hose made of carbon black filled EPDM(ethylene-propylene diene monomer) rubber, a measuring method of crosslink density was established to analyze the aging behaviors under thermo-oxidative stresses. At $125^{\circ}C$, the crosslink density of the rubber specimens decreased slightly in the initial stage, but increased with increasing the aging time. Such variation in crosslink density was similar to that of tensile strength. This might be due to the formation of sulphoxide crosslinks as well as to additional crosslinks made by the reaction of unvalcunized sulfurs. A high temperature aging of rubber specimens at $180^{\circ}C$ caused a slight increase in crosslink density while it did a large decrease in tensile strength and elongation. With aging at high temperature, the formation of carbonyl groups in EPDM molecule chain and formation of sulphoxide crosslink, rather than the crosslink density variation itself, had a large influence on such changes in mechanical property.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.166-174
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• 2014

This research investigated the aging properties of the $B-KNO_3$ system as the igniter. The $B-KNO_3$ system showed the degradation in ignition properties depending on the method and period of storage. It should be found out the cause of the degradation to predict the reliability of the igniters. The changes of the properties by the degradation after aging tests were analyzed by microstructure analysis, XRD analysis and thermal analysis using DSC. It was found out that the lattice parameters of the $KNO_3$ as the oxidizer in the ignition system was changed into the JCPDS values as the aging time increased. Conclusively, the changes of the crystal structure of oxidizer affected the activation energy increasing as aging time increased.

• Journal of the KSME
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• v.43 no.6
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• pp.62-65
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• 2003

이 글에서는 가속 열노화시험을 통하여 노화수명을 예측하고 방법을 고무 재료의 수평 선도와 유한요소해석 결과로 부터 고무부품의 피로숙명을 예측하여 신뢰성을 평가하는 방법을 소개하였다.

• Proceedings of the KIEE Conference
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• summer
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• pp.418-420
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• 2004

전기1급 케이블의 활성화에너지, 가속노화온도 및 가속노화시간 둥을 이용하여 아레니우스(Arrhenius) 방정식에 근거한 케이블 정격온도 및 실제 사용 가능한 운전온도에서 이론적 수명을 계산하고, 정격온도 이외에서의 허용전류를 계산하였다. 또한, 정격온도를 어느 정도 낮추어 사용하면 표준원전에서 기 검증된 전기1급 케이블을 차세대원전 설계수명인 60년간 사용이 가능한지 계산 및 정격온도 감소 적용시 전력케이블 설계영향 둥을 고찰해 보았다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.505-511
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• 2014

The EPDM(ethylene-propylene diene monomer) rubbers used for manufacturing engine radiator hoses can be degraded by locally generated electrical stress in addition to thermal and mechanical stresses. This study presents an accelerated life prediction of the EPDM rubber under electrochemical stresses using the Arrhenius formula under various aging temperatures($60^{\circ}C$, $80^{\circ}C$, and $100^{\circ}C$). The modified life prediction formula considers the relationship between the gradient($E_a/R$) and the Arrhenius constant(C). The effects of tensile strain(5%, 10%) on the life of these rubbers were investigated. The aging temperature influences EPDM rubber life, and tensile strain was predicted. It was confirmed that the modified life prediction was within the data deviation level of the test.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.61-69
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• 2019

Accelerated aging test for the double base propellant was carried out at three different temperatures (60, 70, and $75^{\circ}C$) for over a year. To evaluate the aging characteristics of the double base propellant, the stabilizer contents and thermal decomposition kinetics were analyzed by using high performance liquid chromatography (HPLC) and AKTS-Thermokinetics software. As a result, stabilizer contents in the double base propellant gradually decreased according to the aging temperature and aging duration. The consumption rate of 2-NDPA in the accelerated aged propellants showed that it was two times faster at $75^{\circ}C$ in compared with ther rate at $70^{\circ}C$. These experimental values were simulated by the SB kinetic model, and it was shown that the two-step model with constant reaction orders n1=1 and n2=0 best describes the process of the stabilizer depletion for the double base propellant.

• 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.

• Elastomers and Composites
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• v.44 no.4
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• pp.442-446
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• 2009

Recovery behaviors of unfilled NR, BR, and SBR vulcanizates after aging with a circular deformation were compared to prevent the influence of reinforcing agent. Samples were aged at room temperature, 50, 70, and $90^{\circ}C$ for 10 days. Recovery increased by increasing the measurement time. Instantaneous recoveries less than 1.0 sec were obtained using the recovery variations with the measurement time. For aging at room temperature, difference in the recoveries of the rubber samples was not significant because the aging time was too short. However, for accelerated thermal aging at 50, 70, and $90^{\circ}C$, difference in the recoveries of the rubber samples was significant. Degree of recovery of BR specimen was higher than those of the others, while that of SBR was lowest. However, for accelerated thermal aging at $90^{\circ}C$, recovery of the NR sample was higher than that of the BR one. The initial recovery decreased by increasing the aging temperature and the decrement of SBR was larger than the others. The experimental results were explained with the resilience properties of rubbers and the crosslink density changes by thermal aging.

• Elastomers and Composites
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• v.47 no.1
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• pp.9-17
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• 2012

Herein, life time prediction based on the deterioration of physical properties of chloroprene rubber (CR)aged by heat and seawater was performed. CR samples were experienced an accelerated test at $80^{\circ}C$, $100^{\circ}C$, $120^{\circ}C$ for heat aging, and $40^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ for seawater aging for 20,000 hrs. The change in tensile strength, maximum elongation,hardness was measured. As a result, the decrease in elongation was a major factor causing failure. The life time estimated using an Arrhenius model was 125 years at $23^{\circ}C$ for thermal aging and 9 years at $23^{\circ}C$ for seawater aging. SEM and elemental analysis reveal that cracks were generated and the content of oxygen was increased for CR agined by seawater. FT-IR spectrum shows the new C-O and C = O bonds were generated by the chemical reaction with seawater. Also, the glass transtion temperature was increased and the thermal decomposition was decreased by seawater aging.