• 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.

• 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.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.266-275
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• 2018

Herein, a novel operating life (OL) test method was evaluated with 200 mAh pouch-type lithium-ion batteries. By combining the calendar life (CL) test with intermediate pulse power cycling, more realistic life prediction was possible, which encompassed real operation of batteries accompanying with thermal acceleration. Larger capacity decrease and resistance increase of pouch cell were observed in the OL test, which was well explained using the SEI film growth model. After dissemble of pouch cell, capacity loss and resistance increase mostly occurred within anode, reflecting that SEI film growth on anode surface was highly attributable to cell degradation.

• 한국산업융합학회 논문집
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• 제21권3호
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• pp.141-147
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• 2018

In a time when product development cycles are getting shorter and shorter, many companies are making efforts to develop products with high reliability in a short period of time, accelerated life test is widely used as a method to quickly evaluate reliability. Accelerated life test reduces the test life or the life of the product from the observed data by shortening the lifetime of the product or abruptly lowering the performance under the worse condition than the actual condition in order to shorten the test cost or the test time. In this paper, BL3640A-06P+RB35, DC12V model, which is used in the support device of an automatic rotation type digital signage, which display various information such as textures and images on a display screen in a public place or a commercial space, BLDC motors were subjected to a constant stress test and at the rotational speed of 1rpm, $180^{\circ}$ rotation and reverse rotation under actual use conditions, the stress was imposed on the rotating speed of 2rpm and the weight of the actual installed product from 22.2kgf to 10kgf were installed. The lifetime of the actual use environment condition is 23,545 hours and the rotation speed is accelerated. The life time of the acceleration condition with the additional weight is 1,380 hours. The acceleration factor is calculated as 17.06, the one year guarantee test day is 235 days to 14 days, of the period from 470 days to 28 days, and the third year from 704 days to 42 days. The test date of the BLDC motor was tested on the shortened test date, and the rotational speed and the current value were measured. It is found that there is no defect even if it operates as the test date corresponding to the specified one year warranty period and the 3 year accelerated life test which is experimented. Using the statistical technique of the regression analysis the expected time for the motor to defect to #4 samples was 20 years.

• 대한수학회지
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• 제31권4호
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• pp.709-715
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• 1994

The aim of of the study is a powerful test for the discrimination and therefore an optimal desin for that purpose. This problem is studied by Chernoff ([5]) and used in Chernoff ([6]) for accelerated life tests using the exponential distribution for life times. The approach used here is similar to that suggested by Lauter ([10]) and used in Chaloner ([3]) and Chaloner and Larntz ([4]) where it is motivated using Bayesian arguments. The approach taken in this paper the loss function $L(\cdot)$ evaluating a test procedure and a design d.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권4호
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• pp.236-242
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• 2014

Since permanent magnet coupling transfers power by magnetic force without contact, it has little shock, vibration, noise. In case of overload, it protects a pump or a motor which is relatively important by slipping internally. In this study, failure analysis and test evaluation on the permanent magnet coupling have been proposed and the process that reliability of the product improves through design improvement has been presented. And failure cause of typical failure case has been investigated and improvement plan has been presented. Finally, reliability improvement is established by analysis of the test results of before and after acceleration test.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권4호
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• pp.263-271
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• 2016

Purpose: A slurry pump for flue gas desulfurization system performs a role that discharges the slurry of a plaster shape in a thermal power plant. Since a slurry pump transfers the slurry by the centrifugal force, it has the friction wear in the impeller and liner because of the slurry. Methods: In this study, failure analysis and test evaluation on the slurry pump have been proposed and the process that reliability of the product improves through design improvement has been presented. And failure cause of typical failure case has been investigated and improvement design has been presented. Results: Reliability improvement is established by analysis of the test results of before and after acceleration test. Conclusion: This study can be provided to improve the product reliability through failure analysis of a slurry pump.

• 품질경영학회지
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• 제31권4호
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• pp.194-202
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• 2003

In this paper, we propose goodness of fit test statistics for exponentiality in accelerated life tests data based on Kullback­Leibler information functions. This acceleration model is assumed to be a tampered random variable model. The procedure is applicable when the exponential parameter using the data from accelerated life tests is or is not specified under null hypothesis. And we compare the power of the proposed test statistics with Kolmogorov­Smirnov, Cramer von Mises and Anderson­Darling statistics in the small sample.

• Journal of the Korean Data and Information Science Society
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• 제5권2호
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• pp.87-94
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• 1994

In this paper, we consider optimum plan to determine stress change times under the three-step stress PALTs, assuming that each test units follows an exponential distribution. The tampered random variable(TRV) model for the three-step stress PALTs setup are introduced, and maximum likelihood estimators(MLEs) of the failure rate and the acceleration factors are obtained. The change times to minimize the generalized asymptotic variance(GAVR) of MLEs of the failure rate and the acceleration factors are proposed for the three-step stress PALTs.

• 응용통계연구
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• 제8권2호
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• pp.121-132
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• 1995

정상조건에서 수명이 상당히 긴 다수의 부품으로 구성된 직렬형 시스템의 수명검사를 현실적으로 수행하기 위해 부분적 단계충격 수명검사의 최적 검사계획에 관하여 고찰하였다. 시스템을 구성하고 있는 부품의 수명이 서로 독립인 지수분포를 따르는 것으로 가정하여 각 부품의 고장률과 가속인자의 최우추정량을 구하였다. 또한 각 부품의 고장률과 가속인자에 관한 최우추정량의 일반화 점근분산의 합과 각 부품의 가속인자에 관한 최우추정량의 점근분산의 합을 구하여 이를 최소가 되게 하는 최적변환시점의 결정방법을 제안하였다.