• Journal of Applied Reliability
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• v.18 no.1
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• pp.80-86
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• 2018

Purpose: This article provides a mathematical model for the accelerated degradation test when the performance degradation characteristic follows the lognormal distribution. Method: For developing test plans, the total number of test units and the test time are determined based on the minimization of the asymptotic variance of the q-th quantile of the lifetime distribution at the use condition. Results: The mathematical model for the accelerated degradation test is provided. Conclusion: Accelerated degradation test method is widely used to evaluate the product lifetime within a resonable amount of cost and time. In this article. a mathematical model for the accelerated degradation test method is newly developed for this purposes.

• Journal of Applied Reliability
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• v.5 no.4
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• pp.413-425
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• 2005

As an alternative to traditional life testing, degradation tests can be effective in assessing product reliability when measurements of degradation leading to failure can be observed. This article presents an accelerated degradation testing for vacuum fluorescent displays (VFDs). The accelerated degradation model is based on Arrhenius-lifetime relationship for cathode temperatures. We compare the results between accelerated degradation test and test at normal use condition. Accelerated degradation test for display devices is observed as an efficient method to warrantee product reliability to customers, as well as a tool to save time and costs.

• Journal of Applied Reliability
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• v.10 no.1
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• pp.25-38
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• 2010

In this paper, an accelerated degradation test procedure for an electronic appliance compressor is proposed. We investigate the amount of wear of the compressor and consider several factors as accelerating factors. Finally we select the operating pressure as a main accelerating factor. The test condition of accelerated degradation test is determined. The modified accelerating test reduces the test time in design phase by using the suggested accelerating factor.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.1-8
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• 2022

This study analyzed the characteristics of insulation resistance and operating time based on an accelerated degradation test of a low-voltage circuit breaker. The experimental sample used a molded case circuit breaker (MCCB) and an earth leakage circuit breaker (ELCB). After measuring the insulation resistance of the circuit breakers, the leakage current was affected by an external rather than an internal structure. Furthermore, the insulation resistance of the circuit breakers with accelerated degradation was measured using a Megger insulation tester. In the accelerated degradation test, aging times of five, ten, 15, and 20 years were applied according to a temperature derived using the Arrhenius equation. Circuit breakers with an equivalent life of ten, 15, and 20 years had increased insulation resistance compared to those with less degradation time. In particular, the circuit breaker with an equivalent life of ten years had the highest insulation resistance. Component analysis of the circuit breaker manufactured through an accelerated degradation test confirmed that the timing of the increase in insulation resistance and the time of additive loss were the same. Finally, after analyzing the operating time of the circuit breakers with degradation, it was confirmed that the MCCB did not change, but the ELCB breaker failed.

• International Journal of Reliability and Applications
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• v.17 no.1
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• pp.21-49
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• 2016

Many mechanical, electrical and electronic products have more than one performance characteristics (PCs). For example the performance degradation of rubidium discharge lamps can be characterized by the rubidium consumption or the decreasing intensity the lamp. The product may degrade due to all the PCs which may be independent or dependent. This paper deals with the design of optimal bivariate step-stress partially accelerated degradation test (PADT) with degradation paths modelled by gamma process. The dependency between PCs has been modelled through Frank copula function. In partial step-stress loading, the unit is tested at usual stress for some time, and then the stress is accelerated. This helps in preventing over-stressing of the test specimens. Failure occurs when the performance characteristic crosses the critical value the first time. Under the constraint of total experimental cost, the optimal test duration and the optimal number of inspections at each intermediate stress level are obtained using variance optimality criterion.

• Journal of Applied Reliability
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• v.17 no.1
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• pp.22-27
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• 2017

Purpose: The purpose of this study is to estimate the life time of OLED TV panel through electric current ADT(Accelerated Degradation Test). Methods: We performed accelerated degradation test for OLED TV Panel at the room temperature to avoid high temperature impact on the luminance. Results: we got more accurately the life time of the OLED TV when we applied ADT without temperature factor than including both current and temperature. Conclusion: Until now, the ADT of the OLED TV has been conducted with temperature and current at the same time for reducing test time and costs. We estimate incorrect life time when the temperature is adopted as an accelerated factor. Due to the high temperature impact on the luminance of the OLED TV panel. So as to solve this problem, we discard temperature and use electric current only.

• Journal of Applied Reliability
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• v.17 no.2
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• pp.103-111
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• 2017

Purpose: Accelerated degradation tests can speed time to market and reduce the test time and costs associated with long term reliability tests to verify the required service life of a product or material. This paper proposes a service life prediction method for components or materials using an accelerated degradation tests based on the relationships between temperature and the rate of failure-causing chemical reaction. Methods: The relationship between performance degradation and the rate of a failure-causing chemical reaction is assumed and least square estimation is used to estimate model parameters from the degradation model. Results: Methods of obtaining acceleration factors and predicting service life using the degradation model are presented and a numerical example is provided. Conclusion: Service life prediction of a component or material is possible at an early stage of the degradation test by using the proposed method.

• Journal of Applied Reliability
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• v.13 no.2
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• pp.87-98
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• 2013

Accelerated degradation tests (ADTs) measuring failure-related degradation characteristic at the accelerated condition are widely used to assess the reliability of highly reliable products. Often, however, little degradation could be observed even in single-stress ADTs due to the high reliability of test unit, and as a result poor estimate of the reliability may be obtained. ADTs with multiple stress variables can be employed to overcome such difficulties. In this paper, optimal ADT plans with two stress variables are developed assuming that the degradation characteristic follows Weibull distribution by determining the stress levels, the proportion of test units allocated to each stress level such that the asymptotic variance of the maximum likelihood estimator of the q-th quantile of the lifetime distribution at the use condition is minimized.

• Journal of Applied Reliability
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• v.3 no.2
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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.

• Journal of Korean Society for Quality Management
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• v.45 no.4
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• pp.969-980
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• 2017

Purpose: The purpose of this study was to estimate the lifetime, and verify the target lifetime at steady state temperature, of communication cable jackets used in nuclear power plants. Method: This study was completed according to test and analysis methods required by international standards. After measuring the residual elongation(%) of specimens at specific points in time with the accelerated degradation test, average failure time of each temperature was computed. Thus, the activation energy could be derived by applying the temperature-Arrhenius law to estimate cable jacket lifetime at steady state temperature. Results: The cable jacket lifetime was estimated as 363.8 years assuming a normal nuclear power plant operating temperature of $90^{\circ}C$. Conclusion: To ascertain stable operating conditions for a nuclear power plant, accelerated degradation tests were performed according to the Arrhenius law for components of the nuclear power plants. The lifetime was estimated from the degradation data collected during the accelerated degradation test.