• Journal of Applied Reliability
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• v.9 no.2
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• pp.71-80
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• 2009

This paper discusses the service life prediction methods for CFRP bar for concrete reinforcement using accelerated degradation tests. The relationship between performance degradation and the rate of a failure-causing chemical reaction is assumed for the temperature accelerated degradation tests. Methods of obtaining acceleration factors and predicting service life of the CFRP bar using the degradation model are presented.

• International Journal of Reliability and Applications
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• v.17 no.1
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• pp.85-105
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• 2016

In this paper accelerated life testing is incorporated in quality control technique of acceptance sampling plan to induce early failures in high reliability products.Stress under accelerated condition can be applied in constant-stress, step-stress and progressive-stress or combination of such loadings. A ramp-stress results when stress is increased linearly (from zero) with time. In this paper optimum failure-censored ramp-stress accelerated life test sampling plan for log-logistic distribution has been formulated with cost considerations. The log-logistic distribution has been found appropriate for insulating materials. The optimal plans consist in finding optimum sample size, sample proportion allocated to each stress, and stress rate factor such that producer's and consumer's interests are safeguarded. Variance optimality criterion is used when expected cost per lot is not taken into consideration, and bilevel programming approach is used in cost optimization problems. The methods developed have been illustrated using some numerical examples, and sensitivity analyses carried out in the context of ramp-stress ALTSP based on variable SSP for proportion nonconforming.

• Journal of Applied Reliability
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• v.14 no.2
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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.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.14-19
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• 2005

An accelerated life test (ALT) is used to estimate the reliability of machinery parts and system with a design specification as soon as possible. However, accelerated life test results with simple and severe conditions are inconsistent with physical phenomena in real service condition. Therefore, to assure the safety of the machinery system, it is necessary to establish the appropriate test condition of the ALT of machinery element. In this study, fatigue analysis of the spur gear as a part of the gear box system in the rolling stock was performed. Moreover, based on the results, appropriate test condition of the ALT is developed using both the probabilistic model of the linear damage rule and accelerated durability analysis simulation.

• Journal of Korea Society of Industrial Information Systems
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• v.7 no.2
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• pp.33-39
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• 2002

Accelerated life testing of a car is used to get information quickly on its life distribution. Test cars are no under severe conditions and fail sooner than under usual conditions. A model is fitted to the accelerated failure times and then extrapolated to estimate the life distribution under usual conditions. This paper presents an accelerated test md the reliability growth theory, and applies it to some subsystems of cars during their prototype and pilot testing. The data presented illustrates explicitly the prediction of the reliability growth in the product development cycle. The application of these techniques is a part of the product assurance function that plays an important role in product reliability improvement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.7-11
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• 2003

for many years already, testing laboratories, research institutes and manufactures try to find a reliable water tree accelerated ageing test that is able to show whether a polymer Medium Voltage cable os susceptible to water treeing or not. Test on laboratory samples, model cable designs, and fell size cable are presented. Apart form aging, another important aspect of any accelerated aging test is the right choice of th preconditioning method. THTS paper is the analysis of weibull distribution method after an accelerated aging test of MV(Medium Cable) cable.

• Journal of Applied Reliability
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• v.17 no.2
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• pp.129-135
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• 2017

Purpose: This article provides step-stress accelerated degradation test (ADT) plans based on the Wiener process. Method: Step-stress levels and the stress change times are determined based on the D-optimality criteria to develop test plans. Further, a simple grid search method is provided for obtaining the optimal test plan. Results: Based on the solution procedure, ADT plans which include the stress levels and change times are developed for conducting the reliability test. Conclusion: Optimal step-stress ADT plans are provided for the case where the number of measurements is small.

• Journal of Applied Reliability
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• v.8 no.2
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• pp.75-85
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• 2008

In this paper, we compared domestic with foreign pilot lamps installed on the instrument board or electronic modules (car audio, air-conditional system, etc.) of an automotive vehicle by an accelerated life test in order to estimate the life of domestic pilot lamps. An accelerated life test method was developed and the relation of the life and voltage stress was analyzed. The main results are as follows; i) $B_{10}$ life of pilot lamp is above 5,000 hours, vehicle travel time for 10 years. ii) the life of domestic pilot lamp is longer than that of foreign thing. iii) the life distribution of domestic pilot lamp is wider than that of foreign thing. iv) it is possible to promote import replacement of automobile pilot lamp.

• International Journal of Reliability and Applications
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• v.15 no.2
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• pp.85-98
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• 2014

Accelerated life testing (ALT) is a well famous technique in life testing and reliability studies, this is particularly used to induce so high stress leading to failure of the highly reliable units quickly under stipulated duration of time. The step-stress ALT is one of the systematic experimental strategy of ALT applied to fail the units in steps. In this article we focus on two important issues (i) necessity of life tests at higher steps with relevant causes (ii) to develop a new optimum test plan for 3-step SSALT under the modified cumulative exposure model proposed by Khamis and Higgins (1998). It is assumed that the lifetime of test units follows Rayleigh distribution and its scale parameter at constant stress level is assumed to be a log-linear function of the stress. The maximum likelihood estimates of the parameters involved in the step-stress ALT model are obtained. A simulation study is performed for numerical investigation of the proposed new optimum plan 3-step, step-stress ALT. The necessity of the life test units at 3-step step-stress is also numerically examined in comparison to simple step-stress setup.

• Journal of the Korea Safety Management & Science
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• v.12 no.4
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• pp.61-66
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• 2010

Organic light emitting diode(OLED) has been developed fast from 1963 when electric light emitting phenomenon was discovered. PMOLED(passive matrix OLED) is producted earlier than AMOLED(active matrix OLED). PMOLED is mainly mounted at sub display, but AMOLED is mounted at main display. Nowadays AMOLED is expanded to PMP(portable multimedia players), navigation and TV market. Even thought OLED's market is opening to many applications, OLED's life is worried until now. If we know about OLED's real life, we need time to test so much time over 20,000hrs. Realistically, there is difficult to test such as long time with products from the information-technology sector having a short life cycle. In this paper, we study about OLED's accelerated test to reduce life test by current. We can design OLED's accelerated life model by the result of test. The model consists of design variables like ratio of light emitting, organic material structure, condition of aging, etc. In conclusion, this model can be applied to study about organic material, machine and manufacturing process etc, and also it's possible to develop a method of manufacturing process & materials, so we need to study on the subject of this paper continuously.