• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2004년도 정기학술대회
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• pp.227-232
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• 2004

The failure of geogrids can be defined as an excessive creep strain which causes the collapse of slopes and embankments. In this study, the accelerated creep tests were applied to two different types of polyester geogrids, at 75, 80, 85$^{\circ}C$ by applying 50% load of ultimate tensile strengths using a newly designed test equipment which is allowed the creep testing at higher temperatures. And then the creep curves were shifted and superposed in the time axis by applying time-temperature supposition principles. In predicting the lifetimes of geogrids, the underlying distribution for failure times were determined based on identification of the failure mechanism. The results indicate that the conventional procedures with the newly designed test equipment are shown to be effective in prediction of the lifetimes of geogrids with shorter test times. In addition, the predicted lifetimes of geogrids having different structures at various creep strains give guidelines for users to select the proper geogrids in the fields.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권2호
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• pp.91-103
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• 2012

Tubular markers for road safety facilities are used to lead the driver's sight line and separate the lanes on the road. Such tubular markers are usually installed on the road and frequently hit by vehicles, they are accordingly requested to assure the product durability. The traditional evaluation method of tubular markers include only quality tests of the material properties. However, most of consuming agencies in charge of road management at fields have proposed problems on long-term performance of the products hit by vehicles under various weather conditions. Therefore, the objectives of this study are to develop the reliability test methods and equipments to simulate the product failures of tubular markers due to vehicle collision and wheel compression and the delamination and discoloration of reflection sheets attached on the surface of the products under high and low temperatures.

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권1호
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• pp.67-75
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• 2015

Differential pressure sensor for DPF (Diesel Particulate Filter) is the important part of a automobile exhaust system. This device measures the pressure of before DOC and after DPF to determine whether the DPF regenerate. In this paper reliability assessment criteria for DPF differential pressure sensor are established on terms of quality calcification test and lifetime test. The former quality certification test comprises general performance test and environmental test. Items which pass the test undergo lifetime test which guarantees the extent of mean lifetime with certain confidence.

• 대한기계학회논문집A
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• 제39권9호
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• pp.871-877
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• 2015

다양한 기계부품과 센서류가 포함된 수중로봇, 무인 잠수정 등과 같은 심해장비 시스템은 수심에 따른 높은 수압과 온도, 조류 등 심해의 복합적인 극한 환경조건의 영향을 받기 때문에 실제 현장에서 사용되기 전에 제품의 신뢰성을 검증하는 것이 매우 중요하다. 이러한 복합적인 해양환경을 재현하여 제품에 대한 실증적인 시험을 할 수 있는 시험장비의 구축이 요구되는 실정이다. 본 연구를 통하여 최대수압 2.0MPa, 수온 $5{\sim}60^{\circ}C$, 최대유속 2 m/s의 복합 환경조건의 구현이 가능한 워크인 타입의 수중복합 환경시험장비를 구성하는 주요 구성품의 개발 요구사양 및 설계방안을 제시하고 이를 통해 심해장비 시스템 및 모듈 부품에 대한 제품 신뢰도를 검증할 수 있는 시험장비의 개발 내용을 제시하고자 한다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권3호
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• pp.165-176
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• 2012

Hydrostatic bearing improves performance and life time of a product by avoiding solid friction and reducing viscosity friction with the help of creating pressure equilibrium between two faces doing relative motion. This study suggests failure analysis and test evaluation for a ball joint that adopts the hydrostatic bearing and introduces the entire process to improve reliability of the product by design improvement. A typical failure is growth of friction torque by solid friction, and its failure cause is determined and the improvement is proposed. Finally, reliability improvement is established by analysis of the results of before and after acceleration test.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.10-14
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• 2001

In order to assess the long-tenn reliability of polymer insulators for distribution power systems, we have developed the accelerated aging test method which can simulate the operation conditions. In this study, 3000 hours aging test for 4 kinds of polymer insulators has been completed by the developed accelerated aging test. After 3000 hours aging test, visual inspection and electrical tests were carried for identifying a change of characteristics. Some specimens showed the surface erosion and the manufacturing defect. In the electrical tests, the wet flashover voltage was significant1y decreased by the accelerated aging test. In comparison with the field-aged polymer insulators, it can be concluded that the developed test method can evaluate the long-tenn reliability within short time and screen the manufacturing defect.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권2호
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• pp.127-140
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• 2011

This paper presents an accelerated life test of aviation taxiway lights installed in the airport to help safe navigation of airplanes at night or in bad weather. Recently halogen lamps of taxiway lights are replaced by LED ones and their reliability needs yet to be verified. Thus, effective test conditions are designed reflecting the failure modes and mechanisms from the previous studies on LED, which include the accelerated degradation process. The test is performed under the temperature $70^{\circ}C$ and $90^{\circ}C$ for two types of LED lights, taxiway center line lights(TCLL) and taxiway edge lights (TEDL). The failure time data were analyzed using lognormal distribution and Arrhenius model to find the life-stress relationship, acceleration factor and life characteristics under the normal condition temperature $30^{\circ}C$.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.369-374
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• 2004

Web-based analysis programs for reliability assessment of machine tools were developed in this study. First, the reliability data analysis program was developed to search for failure rate using failure data and reliability test data of mechanical part. Second, failure mode analysis was developed through performance tests like circular movement test vibration test for machine tools. This analysis program shows correlation between failure mode and performance test result. Third, tool life was predicted by correlation between flank wear and cutting time, using the extended Taylor tool life equation in turning data and the equivalently converted equation in order to apply ball endmill data to Taylor tool life equation in milling data. All the information related to input and result data can be stored in theses programs.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.386-390
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• 2007

At recent times, an essential issue in the replacement of the old analogue I&C to computer-based digital systems in nuclear power plants becomes the quantitative software reliability assessment. Software reliability models have been successfully applied to many industrial applications, but have the unfortunate drawback of requiring data from which one can formulate a model. Software that is developed for safety critical applications is frequently unable to produce such data for at least two reasons. First, the software is frequently one-of-a-kind, and second, it rarely fails. Safety critical software is normally expected to pass every unit test producing precious little failure data. The basic premise of the rare events approach is that well-tested software does not fail under normal routine and input signals, which means that failures must be triggered by unusual input data and computer states. The failure data found under the reasonable testing cases and testing time for these conditions should be considered for the quantitative reliability assessment. We presented the quantitative reliability assessment methodology of safety critical software for rare failure cases in this paper.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1-6
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• 2007

A train is subject to a series of reliability-related tasks through its entire life cycle. Among them the reliability demonstration is required for commercial trains and the test is performed during the commissioning period or the early stage of the commercial operation. On the other hands various test are carried out for prototype trains and hence their operational condition is quit different from that of the commercial trains. One should take account of these differences when reliability assessment is needed for the prototype trains. This paper presents a procedure and an analysis method to evaluate reliability of a prototype train. Reliability data have been obtained through test runs of the HSR-350x and operational conditions for the KTX and HSR-350x have been analyzed to compare the reliability targets of the prototype train.