• 한국산학기술학회논문지
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• 제7권3호
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• pp.393-397
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• 2006

신제품에 대한 개발 주기가 짧아지고 있는 현시점에서 제품의 수명을 예측하고 평가하기 위한 방법으로 가속 수명시험과 시험을 통해 관측된 고장 데이터의 분석에 대한 관심이 증대되고 있다. 이에 따라 가속 수명시험을 위한 시험 조건과 고장 데이터의 정확한 분석을 위한 고장 데이터의 최적 분포 결정 방법에 대한 관심 또한 증대되고 있다. 따라서 본 논문에서는 고장 데이터를 기반으로 신뢰성 예측을 할 때 사용하는 분포 함수 결정을 위한 방법으로 관측된 고장 데이터만의 분포를 고려하는 Anderson-Darling 방법과 관측된 고장 데이터의 수명-스트레스 관계식을 적용하여 고장 데이터의 분포를 결정하는 Likelihood Function 방법을 비교한다. 두 가지 방식을 비교한 결과 각 방식에 의해 선택되는 최적분포가 다르며, 따라서 각 방식에 의해 선택된 최적 분포에 의해서 예측되는 수명도 다름을 알 수 있다.

• Journal of the Korean Data and Information Science Society
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• 제17권4호
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• pp.1375-1386
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• 2006

In life testing, the lifetimes of test units under the usual conditions are so long that life testing at usual conditions is impractical. Testing units are subjected to conditions of high stress to yield informations quickly. In this paper, the inferences of parameters on the three step-stress accelerated life testing are studied. The two-parameter exponential distribution with a failure rate function that a log-quadratic function of stress and the tempered failure rate model are considered. We obtain the maximum likelihood estimators of the model parameters and their confidence regions. A numerical example will be given to illustrate the proposed inferential procedures.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권1호
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• pp.21-28
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• 2014

This paper presents an accelerated life test to estimate the lifetime of thermoelectric module for home water purifier. Clamping force and thermal cycle are selected as accelerating variables through the technical review about failure mechanism. It is assumed that its lifetime follows weibull distribution. The relationship, acceleration factor, and BP life at design condition are estimated by analyzing the accelerated life test data.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권2호
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• pp.93-96
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• 2014

RFID (Radio Frequency IDentification) system is recognition technology which can maintain various object's information. Reliability of RFID tags is the most important factor in RFID system. In this paper, we proposed ALT (Accelerated Life Test) method for UHF RFID tags. Temperature and humidity were adopted as stress factors and the accelerated life tests were conducted in three different conditions. We performed failure analysis for identifying failure mechanism and statistical analysis of test data. In the statistical analysis, we employed Inverse Power law for relationship between tag's life and stress. Through the statistical analysis, we proposed acceleration factor for several levels of temperature-humidity. The reliability qualification test plans were also designed for the tag's target reliability.

• 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 $30^{\circ}C$.

• 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.

• 품질경영학회지
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• 제24권4호
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• pp.29-43
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• 1996

This paper identifies these data by the data diagnosis in lognormal distribution and presents the method to obtain exact parameter estimates and confidence intervals of regression line. The life-stress relationship uses Arrhenius model and life data generate Class-H insulation complete data by simulation. Also, the method to estimate parameters uses least squares estimation and externally Studentized residuals can be used as test statistics for identifing outliers. And influential cases are identified by Cook's distance. This research is intended to obtain the useful information for the life of products and test method, to save time and costs, and to help optimum accelerated life test plans.

• Journal of the Korean Data and Information Science Society
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• 제23권4호
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• pp.843-850
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• 2012

The inferences of data obtained from periodic inspection and type I censoring for the three step stress accelerated life test are studied in this paper. The failure rate function that a log-quadratic relation of stress and the tampered failure rate model are considered under the exponential distribution. The optimal stress change times which minimize the asymptotic variance of maximum likelihood estimators of parameters is determined and the maximum likelihood estimators of the model parameters are estimated. A numerical example will be given to illustrate the proposed inferential procedures.

• 대한기계학회논문집A
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• 제41권10호
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• pp.997-1004
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• 2017

엘리베이터 와이어로프의 수명은 제품의 매우 중요한 특성 가운데 하나로서 사용자의 안전 및 장비의 정비 정책과 밀접한 관계가 있다. 엘리베이터 와이어로프의 수명을 사용조건에서 측정하는 것은 매우 비경제적이다. 이 연구에서는 엘리베이터 와이어로프 (8x19W-IWRC)의 가속열화시험 데이터를 활용하여 와이어로프의 수명을 추정하는 방법을 다루었다. 굽힘피로시험기를 이용하여 가속열화시험을 진행하였으며 가속변수로는 인장하중을 사용하였다. 와이어로프의 수명은 대수정규분포를 가정하였고, 선형회귀모형을 이용하여 가수명을 구한 후 가속수명모형을 이용하여 와이어로프의 수명을 추정하는 방법과 고장 확률에 대한 로지스틱 회귀모형을 이용하여 추정하는 방법을 제시하고 두 모형의 수명 추정결과를 비교하였다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제3권2호
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• pp.103-116
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• 2003

We carry out reliability tests and investigate the failure mechanisms. of the wafer level vacuum packaged MEMS gyroscope sensor using an accelerated degradation test. The accelerated degradation test (ADT) is used to evaluate reliability (and/or life) of the MEMS vacuum package and to select the accelerated test conditions, which reduce the reliability testing time. Using the failure distribution model and stress-life model, we are able to estimate the average life time of the vacuum package, which is well agreed with the measured data. After improving several package reliability issues such as prevention of gas diffusion through package, we carry out another set of accelerated tests at the chosen acceleration level. The results show that reliability of the vacuum packaged gyroscope has been greatly improved and can survive without degradation of performance, which is the Q-factor in gyroscope sensor, during environmental stress reliability tests.