• 한국군사과학기술학회지
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• 제15권2호
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• pp.215-223
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• 2012

A violet smoke hand grenade(KM18) is used to generate signals. The grenade is considered to fail when its smoke emission time is longer than the specified one so that its smoke concentration becomes lighter. Accelerated degradation test for the grenade was performed, and then failure in smoke emission time was reproduced from the test. Stress for the degradation test was selected as temperature/humidity from the pre-test results. Degraded data of emission time from the accelerated test were analyzed through applying a distibution-based degradation model. Then, Peck Model was applied to predict the storage life under field conditions. In addition, the predicted storage life was compared with that of ASRP(Ammunition Stockpile Reliability Program).

• Corrosion Science and Technology
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• 제4권4호
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• pp.147-154
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• 2005

The creep resistance of geogrids is one of the most significant long-term safety characteristics used as the reinforcement in slopes and embankments. The failure of geogrids is defined as creep strain greater than 10%. In this study, the accelerated creep tests were applied to polyester geogrids at various loading levels of 30, 50% of the yield strengths and temperatures using newly designed test equipment. Also, the new test equipment permitted the creep testing at or above glass transition temperature($T_g$) of 75, 80, $85^{\circ}C$. The time-dependent creep behaviors were observed at various temperatures and loading levels. And then the creep curves were shifted and superposed in the time axis by applying time-temperature supposition principles. The shifting factors(AFs) were obtained using WLF equation. In predicting the lifetimes of geogrids, the underlying distribution for failure times were determined based on identification of the failure mechanism. The results confirmed that the failure distribution of geogrids followed Weibull distribution with increasing failure rate and the lifetimes of geogrids were close to 100 years which was required service life in the field with 1.75 of reduction factor of safety. Using the newly designed equipment, the creep test of geogrids was found to be highly accelerated. Furthermore, the time-temperature superposition with the newly designed test equipment was shown to be effective in predicting the lifetimes of geogrids with shorter test times and can be applied to the other geosynthetics.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권1호
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• pp.37-45
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• 2009

Recently mechanical watt-hour meters are being replaced by electronic watt-hour meters. The replacement period of mechanical watt-hour meters is 7 years. This period is based on long term historical data. The replacement period of electronic watt-meters is also 7 years. This period is determined using the replacement period of mechanical watt-hour meters. However lifetime of mechanical watt-hour meters is different from the lifetime of electronic meters. In order to determine desirable replacement period of electronic watt-hour meters, accelerated life tests of major components in electronic watt-hour meters were performed. The test results showed that LCD was the component which had the shortest lifetime. In this paper, lifetime of electronic watt-hour meters manufactured by 3 company was estimated and life test standard for LCD was developed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.722-727
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• 2004

The gear that is used in various mechanical components occurs easily damages due to the repeated torque and the high oil temperature. The main failure mode of the gear is the surface deterioration with the tooth surface fatigue. Therefore, the life evaluation and the failure analysis of the gear were very important since it may cause fatal damage of entire gear box system. In this paper, the failure mechanism and the life of the gear were evaluated using the durability analysis simulator such as MSC.FATIGUE. Moreover, the reliability analysis model of the spur gear with the accelerated life testing technique was proposed.

• 펄프종이기술
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• 제45권1호
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• pp.1-5
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• 2013

Printing papers published in between 1950's and 1990's were treated with three methods such as distilled water washing, $CaCO_3$ solution washing and methyl cellulose solution coating for improving their conservational properties. Accelerated aging with $80^{\circ}C$ and 80% RH for 14 days was applied to the testing papers. Results showed that distilled water and $CaCO_3$ washing kept increased pH even after accelerated aging, but did not improve folding endurances for 1950's-60's papers. Methyl cellulose treatment did not increased pH of the old papers, but increased folding endurances remarkably for 1950's-60's papers even after accelerated aging. It suggests that methyl cellulose treatment after $CaCO_3$ washing should give improvements both in pH and folding endurance.

• 한국안전학회지
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• 제27권4호
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• pp.13-19
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• 2012

The purpose of this study is to extract the major factors related to the deterioration mechanism of white organic light-emitting diodes(WOLED) by performing accelerated testing of temperature, voltage, time, etc., and to develop an accelerated life test(ALT) model. The measurement results of the brightness of the WOLED exhibited that their average brightness tended to increase as the operating voltage increased and that the half-life period of the brightness appeared after approximately 400 hours when the operating voltage was 20V and the ambient temperature was $85^{\circ}C$. It could be seen that although the WOLED showed comparatively the same brightness when the initial acceleration began after the operating voltage was applied to it, its brightness changed excessively after the WOLED's thermal storage had been made. In addition, it was observed that the half-life period was reduced as the ambient temperature and applied voltage increased. The strength of the WOLED which had been maintained in the range of visible light at the maximum load was reduced by the deterioration of the organic light emitting material due to the influence of the operating voltage and temperature, and the reduction of emitted light was small at low voltage and temperature. It could be seen that the failure of the WOLED during the ALT was caused by wear due to load accumulation over time, and that Weibull distribution was appropriate for the life distribution and acceleration was established between test conditions. From the WOLED analysis, it is thought that factors influencing the brightness deterioration are voltage, temperature, etc., and that comprehensive analysis considering discharge control, dielectric tangent margin, etc., would further increase the reliability.

• 한국군사과학기술학회지
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• 제21권6호
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• pp.894-903
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• 2018

In the case of helicopters, the development of parts technology is rapidly changing, and the complexity is rapidly increasing. Particularly, the surge of various electric and electronic systems is recognized as a problem that is directly related to the safety of the helicopter. Due to these problems, there is a growing interest in reliability evaluation in the face of the problem of confirming and certifying the reliability of parts in the development stage. In this paper, the analysis of the failure mechanism of the wiper system was carried out, and the priority and importance of each failure mode were checked by using the results, and major stress factors were derived and the corresponding acceleration model was selected. Also, the accelerated lifetime test time was calculated according to the life test time, acceleration status and acceleration level of the steady state by using the selected acceleration model and characteristic values.

• Journal of Power Electronics
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• 제17권3호
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• pp.811-820
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• 2017

The reliability issue of IGBT is a concern for researchers given the critical role the device plays in the safety of operations of the converter system. The reliability of power devices can be estimated from the intermittent life test, which aims to simulate typical applications in power electronics in an accelerated manner to obtain lifetime data. However, the test is time-consuming, as testing conditions are not well considered and only rough provisions have been made in the current standards. Acceleration of the test by changing critical test conditions is controversial due to the activation of unexpected failure mechanisms. Therefore, full investigations were conducted on critical test conditions of intermittent life test. A design optimization process for IGBT intermittent life testing program was developed to save on test times without imposing additional failure mechanisms. The applicability of the process has been supported by a number of tests and failure analysis of the test results. The process proposed in this paper can guide the test process for other power semiconductors.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.62-68
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• 2016

Feeder cable assembly는 정보통신용 자동차부품이다 기능을 제대로 하지 않으면 자동차의 제어와 안전에 큰 문제가 발생한다. 가속수명시험은 시험시간을 단축할 목적으로 짧은 시간에 잠재적인 고장모드와 고장을 찾기 위하여 기속조건(스트레스, 스트레인, 온도 등)에서 실험을 실시하는 것이다. 고장원인은 부품의 품질과, 고장으로 유도하는 공정, 디자인에 의해 발생하는 결함이다. 열충격은 온도차에 의하여 부품의 열팽창 정도가 다른 것에 기인한다. 열충격시험은 부품이 급격한 온도차를 견디는 능력을 실험하는 것이다. 본 연구에서는 가속시험의 coffin-manson 식을 이용하여 정상조건(최고온도 $80^{\circ}C$, 최저온도 $-40^{\circ}C$)과 가속조건(최고온도 $120^{\circ}C$, 최저온도 $-60^{\circ}C$)을 이용하여 가속계수를 계산하여 2.25 값을 얻었다. 정상조건에서 1,000 사이클 실험이 가속조건에서 444 사이클 실험만하여도 됨을 알 수 있었다. Bx 수명 식을 이용하여 가속조건에서 시료가 5개, B0.04%.10years 조건에서 747 사이클 결과를 얻었다. 정상조건에서 1,000 사이클, 가속조건에서 747 사이클 실험한 feeder cable assembly 시료 5개를 각각 네크워크 분석기를 이용하여 성능시험을 실시하고, 와이블분포의 모수분포값을 비교한 결과 가속이 잘 되었음을 알 수 있었다. 동등한 신뢰도에서 가속실험을 통하여 시험시간을 1/4 정도 단축할 수 있었다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권3호
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• pp.208-215
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• 2016

Purpose: ASRP for the domestic development guided missiles requires not only for the reliability evaluation of the products in storage but also for the life cycle management of the products including development prototypes and initial production items. Methods: For this purpose, it should be performed to build a performance database before and after the accelerated aging test with shelf life items including development prototypes and initial production items, based on which the lifetime prediction should also be carried out. In addition, HILS must be applied for the acceptance test with the initial and follow-up production items, and also for ASRP for the long-term storage products in order to secure systematic quality assurance. Results: The results for the life cycle reliability Improving of domestic development of guided missiles are DB building of prescription Item performance, active application of HILS, Management associated with guided missiles life cycle and to Secure technology data about the introduction of foreign guided missiles. Conclusion: Furthermore, it is demanded that DTaQ, the managing agency of ASRP, actively take part in the process to maintain reliability engagement consistency over the life cycle of guided missiles.