• 한국신뢰성학회지:신뢰성응용연구
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• 제14권3호
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• pp.182-190
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• 2014

This paper presents new practical accelerated life test plans with different censoring times at three levels of stress for Weibull and lognormal lifetime distributions, respectively. The proposed plans are compared with the corresponding two-level statistically optimal plans and three-level compromise and practical plans. Computational results indicate that new practical plans have been more precise and effective than the existing three-level plans under a constraint of total testing time. In addition, a procedure to determine useful ALT plans is illustrated with a numerical example.

• 전기학회논문지
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• 제66권3호
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• pp.551-556
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• 2017

The cross-linked polyethylene(XLPE) has been most widely used for the power cable insulating layer because of its outstanding properties such as electrical and mechanical properties. However, XLPE is unrecyclable when disposed after replacement and demolishing because it becomes thermosetting through cross-linked process. Recently, because of growing social awareness of recycling and eco-friendly, there is growing need for the development of recyclable insulating materials that can replace XLPE. Therefore, the purpose of this study is to compare the electrical properties of XLPE and recyclable thermoplastic insulating materials. To this end, we compared and analyzed the electrical properties of XLPE and group N2 through AC breakdown test, accelerated water treeing test and accelerated life test(ALT).

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권1호
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• pp.52-59
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• 2015

In this Study, we tested electroluminescent film to accelerate life by temperature, humidity, voltage, and frequency. We analyzed brightness data to estimate activation energy and verify it's suitability. All of the tests performed in operating condition. Because electroluminescent film is mostly degraded by fluorescent in operating condition. Two different sample groups were tested and compared to find common parameter.

• 대한공업교육학회지
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• 제33권2호
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• pp.312-324
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• 2008

상용 냉장고에서 새로 설계된 힌지 키트 시스템(HKS, Hinge Kit System)을 개선하기 위하여 새로운 강인 방법론을 연구하였다. 이 방법은 결함 모드, 시장에서의 메카니즘, 가속수명시험법(ALT, Accelerated Life Test)을 이용한 다양하게 개선된 HKS의 설계변수 등을 고려한 것이다. 시장에서의 결함 반품 조사와 첫 번째 ALT 시험을 통한 공통적 크랙 부위는 HKS의 하우징 부분에서 일어남을 확인하였다. 냉장고 HKS의 초기 설계 단계에서 간과한 설계 변수는 하우징이었다. 이를 통하여 냉장고의 특정 열린 지지 구조에서 모든 열린 지지 구조로 확산하여 설계 수정하는 계기가 되었다. 두 번째 ALT 시험을 통하여 발견한 파괴와 크랙 부위는 비틀림 축에서 발생하였다. 설계 변수에서 비틀림 축의 동심도를 고려치 않았던 것이 원인이었다. ALT 시험 절차를 통하여 간과한 설계 변수를 수정할 수 있었다. ALT 시험의 결과를 통하여 연간 결함 발생률이 약 0.01%였고 재설계된 HKS의 B1 수명은 10년으로 파악되었다. 본 논문에서 사용된 변수 설계 방법은 결함 제품 검사, 하중 분석, 세 번의 ALT 시험 등이며 이들은 기계 시스템의 강인 설계에 매우 효과적임을 알 수 있었다. 향후 본 연구에서 제시된 방법은 새로운 가전제품의 강인 설계에 적용할 수 있을 것으로 사료된다.

• Journal of the Korean Data and Information Science Society
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• 제16권4호
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• pp.923-931
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• 2005

The two parameter generalized exponential distribution was recently introduced by Gupta and Kundu (1999). It is observed that the generalized exponential distribution can be used quite effectively to analyze skewed data set. This paper develops the accelerated life test model using generalized exponential distribution and considers maximum likelihood estimation of parameters under the tampered random variable model. To show the performance of proposed maximum likelihood estimates, some simulation will be performed. Using a real data set, an example will be given.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1355-1360
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• 2008

Stainless steel sheets are widely used as the structure material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. Gas welding is very important and useful technology in fabrication of an railroad car and vehicles structure. However fatigue strength of the gas welded joints is considerably lower than parent metal due to stress concentration at the weldment, fatigue strength evaluation of gas welded joints are very important to evaluate the reliability and durability of railroad cars and to establish a criterion of long life fatigue design. In this paper, ${\Delta}P-N_f$ curve were obtained by fatigue tests. Using these results, the accelerated life test (ALT) is conducted. From the experimental results, an acceleration model is derived and acceleration factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of plug and ring gas welded joints and data analysis by statistic reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.1-8
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• 2011

Stainless steel sheets are widely used as the structure material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. Gas welding is very important and useful technology in fabrication of an railroad car and vehicles structure. However fatigue strength of the gas welded joints is considerably lower than parent metal due to stress concentration at the weldment, fatigue strength evaluation of gas welded joints are very important to evaluate the reliability and durability of railroad cars and to establish a criterion of long life fatigue design. In this paper, ${\Delta}-N_f$ curve were obtained by fatigue tests. Using these results, the accelerated life test (ALT) is conducted. From the experimental results, an acceleration model is derived and acceleration factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of plug and ring gas welded joints and data analysis by statistical reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1667-1672
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• 2007

In order to assess the reliability of the exhaust bellows for automobiles, accelerated life test model and procedure are developed. By using this method, failure mechanism and life distribution are analyzed. The main results are as follows; i) the main failure mechanism is crack or breakage of inner flexible tube by shaken displacement at shear direction. ii) temperature is a second factor to affect a failure. iii) the life distribution of exhaust bellows is fitted well to Weibull life distribution and the shape parameter is 13.3 on condition of shaken displacement and $600^{\circ}C$

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.262-265
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• 1996

An ALT(accelerated life testing) method is to test a product in over-stressed conditions, and then the test result is extrapolated to an usual (normal stressed) condition. It is the major disadvantage of ALT method that the more extrapolation to an usual condition applies the bigger error is indispensable. Therefore a reliability model combining field failure data and laboratory test data is required in pratice. We propose several methods of estimating the failure rate of a product life which is assumed to follow an exponential distribution. Structural similarity and technological advances are also cosidered. Finally, We derive the acceleratio factor which can be used to predict the failure rate for a new product.

• 전기전자학회논문지
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• 제21권3호
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• pp.252-255
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• 2017

고온자전합성과 후열처리 공정으로 $Mo_xW_{1-x}Si_2$ 발열체를 제조하였다. $Mo_xW_{1-x}Si_2$ 발열체의 신뢰성을 검증하기 위해 가속수명시험을 수행하였으며, 수명시간을 Minitab 프로그램으로 추정하였다. 또한, 가속수명시험 후의 $Mo_xW_{1-x}Si_2$ 발열체의 고장분석을 전기적과 구조적 특성으로부터 수행하였다. 그 결과, $Mo_xW_{1-x}Si_2$ 발열체의 지배적인 고장 유형은 발열체 내부의 크랙 형성과 $SiO_2$ 보호층의 박리임을 확인하였다.