• Journal of Advanced Marine Engineering and Technology
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• v.25 no.5
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• pp.1058-1064
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• 2001

In this paper, the development of probability distribution estimation program for fatigue crack growth lives was summarize. The probability distribution estimation program of life was developed to increase the reliability of life estimation. In this study, it is considered that the cause of scatter in fatigue crack growth data is due to material inhomogeneity. The material resistance to fatigue crack growth is modelled as a spatial stochastic process, which varies randomly along the crack path. We developed the GUI program to estimate the probability distribution and reliability using the non-Gaussian stochastic process method. This program can be used for the reliability assessment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.393-397
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• 2006

The study about Accelerated Life Test and analysis of failed data is increased in order to predict and evaluate reliability of products, according as the development cycle of products is reduced. Therefore, the decision of optimal distribution function about failed data for accurate analysis of failed data and test condition for Accelerated Life Test is very important. This paper compares Anderson-Darling method with Likelihood Function method for the decision of optimal distribution function about failed data. Anderson-Darling considers only failed data and Likelihood Function considers both failed data and life-stress relationship in decision of distribution function. In the results of comparison about two methods, we found that the distribution function chosen by each method is different and the life time predicted by each decided distribution function is different.

• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.51-58
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• 2016

In this paper, we present some results on No-failure accelerated life test of aerial vehicle for reliability demonstration. The design of general accelerated life test consists of the three phases: 1) Estimating normal life test time of a single product from Weibull distribution model; 2) Determining the acceleration factor (AF) by utilizing the relation between the life of mechanical components and the applied torque; 3) Calculating the accelerated life test time, which comes from dividing the estimated normal life test time into AF. Then, we applied the calculated life test time to the real reliability test of the flap actuating system, while considering the requirement specification for mechanical components and operating environment of the actuation system. Real experimental processes and results are presented to validate the theory.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.98-99
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• 2021

The number of fires in the Korean distribution warehouse increased by about 350 from 1,070 in 2014 to 1,416 in 2020. In addition, the fire load increases with the scale of the distribution warehouse, and even if the automatic sprinkler operates, there is a limit to the direct intrusion of the water source into the ignition source, and the detector is often installed on a high ceiling. The sensing time is often delayed. In order to improve the fire safety of such distribution warehouses, the US NFPA stipulates in detail the contents related to the facility, such as sprinkler water discharge standards, rack-type warehouse installation height restrictions, and regulations on collection and equipment. However, in Japan, the goods loaded inside the distribution warehouse are not classified in detail, and it is considered that the fire safety for the distribution warehouse is low due to the relaxation regulations of the fire prevention section. Therefore, in this study, common problems are classified into material, spatial, and safety management characteristics through the cases of distribution warehouse fires that occurred in Korea and abroad, and the problems related to distribution warehouses in Korea and abroad are compared and analyzed. And present basic materials for improving the life safety standards of future distribution warehouse facilities.

• Journal of the Korean Data and Information Science Society
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• v.17 no.4
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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.

• Journal of Applied Reliability
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• v.4 no.1
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• pp.15-26
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• 2004

Life test is performed to set a confidence (lower) limit on the mean or median life of items if the number of failures at the end of the fixed time t does not exceed a given number c. Gupta(1962) propose a sampling plan for truncated life tests when the life distribution of an item is normal or lognormal distribution. In this paper, based on the result of Gupta(1962), we propose a sampling plan for failure rate test when an item has normal or lognormal life distribution. We assume that the shape parameter is known while the location parameter is unknown.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.804-811
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• 2010

The fatigue crack propagation is stochastic in nature, because the variables affecting the fatigue behavior are random and have uncertainty. Therefore, the fatigue life prediction is critical for the design and the maintenance of many structural components. In this study, fatigue experiments are conducted on the specimens of magnesium alloy AZ31 under various conditions such as thickness of specimen, the load ratio and the loading condition. The probability distribution fit to the fatigue failure life are investigated through a probability plot paper by these conditions. The probabilities of failure at various conditions are also estimated. The fatigue design life is predicted by using the Weibull distribution.

• Proceedings of the Korean Reliability Society Conference
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• 2004.07a
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• pp.167-175
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• 2004

A nonparametric procedure is proposed to test the exponentiality against the hypothesis that one life distribution has a greater residual life times than the other life distribution. Such a hypothesis turns out to be equivalent to the one that one failure rate is greater than the other and so the proposed test works as a competitor to more IFR tests by Kochar (1979, 1981) and Cheng (1985). Our test statistic utilizes the U-statistics theory and a large sample nonpara metric test is established. The power of the proposed test is discussed by calculating the Pitman asymptotic relative efficiencies against several alter native hypotheses. A numerical example is presented to exemplify the proposed test.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.843-846
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• 2015

In this paper, the failure mechanism of PTC heater were examined closely by failure analysis and based on it, accelerated life test were conducted. Finally, life distribution and acceleration model were established. The failure mechanism of PTC heater such as crack, increase of resistance due to heating were identified. Two acceleration factors such as temperature, humidity were chosen with two levels each and accelerated life test were done. Life distribution were identified as Weibull distribution with shape parameter 5.4 and Temperature-Humidity model was fitted as an acceleration model.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.1
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• pp.1-7
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• 2020

In general, an inspection schedule is established based on the long-term fatigue life during the design stage. However, in the design stage, it is difficult to clearly identify the uncertainty factors affecting long-term fatigue life. In this study, the probabilistic fatigue life assessment was conducted in accordance with the methodology of DNV-GL. Firstly, The initial crack distribution estimated through the initial crack propagation analysis was updated by reflecting the results of crack inspection. Secondly, the updated crack distribution was compared with the initial crack distribution, and the probability of failure was updated with the effect of crack inspection.