• 대한기계학회논문집A
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• 제36권7호
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• pp.751-757
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• 2012

사용조건에서 수명시험을 수행할 경우 시험시간이 많이 소요되므로 사용조건보다 가혹한 스트레스 조건을 추가하여 가속수명시험을 수행하면 시험시간을 단축시킬 수 있다. 수명에 영향을 미치는 스트레스를 선정하여 각 스트레스의 사용조건과 가속조건에서 시험을 수행할 경우 가속 스트레스간에 교호작용이 존재할 수 있다. 그러나 기존의 연구에서는 2가지 이상의 가속 스트레스를 부과하여 가속수명시험을 수행할 경우 교호작용을 고려하지 않은 경우와 가속 수명에 대한 모델식을 제시한 연구들이 대부분이다. 본 논문에서는 기계류 부품의 수명에 영향을 미치는 가속 스트레스를 선정한 후 교호작용을 고려한 시험계획에 따라 가속수명시험을 수행한 자료를 이용하여 가속 계수와 가속 스트레스간의 관계식을 산출하는 방법을 제시하고자 한다. 또한 본 논문에서 제시한 교호작용을 고려한 가속시험방법과 가속 계수를 산출할 수 있는 모델식을 이용하여 복합적인 가속수명시험 수행시 쉽게 적용하고 결과를 산출할 수 있는 기초가 될 것으로 기대된다.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.75-82
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• 2005

In this paper, accelerated life testing(ALT) method and procedures for a are developed and applied to assess the reliability of the product. Relay is a device that can open and close the electric circuit electrically and is used for protecting and controlling the load. In this study, an accelerated life test method for predicting the mechanical life of a relay is developed using the relationship between stresses, failure mechanism and life characteristics of products. Using the ALT method, we performed life tests and analyzed the tests results. The proposed method and procedures may de extended and applied to testing similar kinds of products to reduce test times and costs of the tests remarkably.

• 대한산업공학회지
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• 제25권4호
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• pp.517-526
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• 1999

This paper deals with two economic optimal designs of constant-stress accelerated life test(ALT) where failure distribution follows one of location-scale family, i. e., exponential, Weibull, and lognormal distributions which have been ones of the popular choices of failure distributions. Two optimization criteria to develop ALT plans are the statistical efficiency per unit expected cost which consists of the fixed test cost, cost being proportional to the number of test units, and variable test cost depending on test period and stress level, and the expected loss which combines Taguchi's quadratic loss function and expected test cost. Optimum plan determines the low stress level, test units allocated to each stress, and censoring times at two stress levels under Type I censoring. The proposed ALT plans are illustrated with a numerical example and sensitivity analyses are conducted to study effects of pre-estimates of design parameters.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권2호
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• pp.112-121
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• 2017

Purpose: The most previous works on designing accelerated life tests (ALTs) are focused on the application of a single stress. Because of the difficulty to obtain the sufficient information in a reasonable duration using single stress only, there is needed in practice to use multiple-stress ALTs frequently. This paper presents new practical plans with two stresses for Weibull distribution. Methods: The four-level practical plans based on rectangle test region are proposed and compared with the corresponding three-level statistically optimal plans. Sensitivity analyses for assumed design parameters and life-stress relationship are conducted. Results: A procedure to choose practical ALT plans is illustrated with a numerical example and guidelines for planning two-stress ALTs are provided. Conclusion: The proposed two-stress ALT plans on practical constraints to assess a quantile of Weibull lifetime distribution at the use condition are efficient and robust.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2008년도 추계학술대회
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• pp.153-160
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• 2008

This paper presents the log likelihood function for integrated models for ALT such as exponential-general Eyring, Weibull-temperature and specific heat, lognormal-temperature and specific heat. Additionally this paper estimates the system reliability and mean time to failure(MTTF) for series, parallel, k of n, and standby system using ALT linkage parameter. Lastly this study designs three variable reliability acceptance sampling(RAS) plans such as type I, II censored test, sequential test by the use of integrated models for ALT.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.327-337
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• 2005

Accelerated life test models and procedure are developed to assess the reliability of Door switch. The main function of door switch is to operate bulb lamp and fan motor. The accelerated life test method and test equipments are developed using the relationship between stresses and life characteristics of the products. Using the developed accelerated life test method, the parameters of the ALT model and life time distribution are estimated and the reliability of the Door S/W at use condition if assessed. The proposed accelerated life test method and procedure may be extended and applied to testing similar kinds of products to reduce test time and costs of the tests remarkably.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2004년도 정기학술대회
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• pp.129-137
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• 2004

This paper presents an accelerated life test for burnout of tungsten filament of incandescent lamp. From failure analyses of field samples, it is shown that their root causes are local heating or hot sports in the filament caused by tungsten evaporation and wire sag. Finite element analysis is performed to evaluate the effect of vibration and impact for burnout, but any points of stress concentration or structural weakness are not found in the sample. To estimate the burnout life of lamp, an accelerated life test is planned by using quality function deployment and fractional factorial design, where voltage, vibration, and temperature are selected as accelerating variables. We assumed that Weibull lifetime distribution and a generalized linear model of life-stress relationship hold through goodness of fit test and test for common shape parameter of the distribution. Using accelerated life testing software, we estimated the common shape parameter of Weibull distribution, life-stress relationship, and accelerating factor.

• 한국신뢰성학회지:신뢰성응용연구
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• 제5권2호
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• pp.221-239
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• 2005

General chip SMD parts(chip resistance, chip capacitor, chip varistor etc.) are very wide used electronics parts for IT units. But, failure modes are indistinct for these chip parts. In factory and field the failure modes are recognized to accidental failure mode caused by potential defect. In this paper used chip varistor ALT(Accelerate Life Test) test for verify general failure modes in chip SMD parts. Also the results are useful for general chip SMD ALT tests.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.51-67
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• 2005

General chip SMD parts(chip resistance, chip capacitor, chip varistor etc.) are very wide sed electronics parts for IT units. But, failure modes are indistinct for these chip parts. In factory and field the failure modes are recognized to accidental failure mope caused by potential defect. In this paper used chip varistor ALT(Accelerate Life Test) test for verify general failure modes in chip SMD parts. Also the results are useful for general chip SMD ALT tests.

• Tribology and Lubricants
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• 제30권5호
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• pp.271-277
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• 2014

Hydraulic reciprocating seals have been widely used to prevent fluid leakage and to provide lubricant film on counter surface in various hydraulic system. The degradation of the seal may cause the catastrophic failure of the hydraulic system. To assess the durability of the seals and the compatibility with counter surface, accelerated life testing (ALT) has been typically employed from industry. However, ALT often takes up to a few months to cause a failure of the seals, and therefore, there is a need to develop more efficient ALT methods. In this work, the degradation characteristics of polyurethane (PU) seals from field test are investigated and they are compared to those from the component and bench tests, with an aim to contribute to the development of ALT method. From the comparison of the cross-sectional profiles of the sealing surface of the PU specimens before and after the tests, both wear and compression set are found to be responsible for degradation of the PU seals. It is also shown that the major wear mechanisms of the PU seals from the field is abrasive wear and formation of pits. The component and bench tests performed in this work are shown to reproduce such wear mechanisms, and therefore, those test methods can be used as an ALT method for PU seals. In particular, the bench test proposed in this work may be effectively utilized to assess the durability and the compatibility of the seals with the counter surface. The results of this work are expected to aid in the design of ALT for PU seal.