• 한국공작기계학회논문집
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• 제15권4호
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• pp.63-68
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• 2006

This research presents the reliability analysis of the pneumatic actuator within the tape feeder that is used to transfer the correct force to linked parts during l.0E+7 cycles. First, the degradation analysis for thrust and air leakage is executed to obtain the failure data of a product based on its performance over time. Second, once the parameters has been calculated using the weibull 2-parameter distribution and MLE(Maximum Likelihood Estimation), information related to life such as reliability, failure rate, probability density function is estimated. Finally, MTTF(Mean Time To Failure) and $B_{10}$ life of actuators are calculated. MTTF means the mean life at the confidence level and $B_{10}$ life refers to the time by which 10% of the product would fail. In this study, failure causes and solutions are examined using the reliability analysis.

• 한국정보전자통신기술학회논문지
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• 제11권6호
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• pp.645-650
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• 2018

소프트웨어 안정성은 운영 환경에서 시간의 흐름에 따른 오작동이 없이 운영 될 수있는 가능성이라고 할 수 있다. 소프트웨어의 고장 분석을 위한 유한 고장 NHPP에서, 고장 발생률은 일정하거나 단조롭게 증가하거나 단조 감소하는 추이를 나타낼 수 있다. 본 연구에서는 NHPP 모형에 근거하고 소프트웨어 고장시간 자료를 바탕으로 와이블 분포의 형상모수를 고려한 지수분포 Rayleigh 분포, 역-지수 분포를 수명분포로 하여 소프트웨어 개발 비용모형에 관한 속성을 비교 평가분석을 하였다. 또한 모수 추정은 최우 추정방법을 적용하고 데이터 추세검정은 박스-플롯방법을 이용하였다. 본 연구의 결과는 Rayleigh 모형이 역-지수 모형이나 Goel-Okumoto 모형에 비교해서 방출 시기는 Rayleigh 모형이 가장 빠르고 방출시점의 비용도 가장 경제적임을 알 수 있다. 이 연구의 결과를 이용하면 소프트웨어 개발자 및 운용자들은 최적방출시간과 경제적인 개발비용을 예측 하는데 활용 할 수 있으리라 판단된다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제8권2호
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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.

• 한국기계가공학회지
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• 제11권5호
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• pp.1-7
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• 2012

The transportation is almost dependent on a single fuel petroleum with transportation energy dilemma. Hybrid Electric Vehicle(HEV) technology holds more advantages on efficiency improvements for petroleum consumption at the transportation. And bearing is recognized as the important component of gearbox. Gearboxes for HEV transmission have been ensured the highest reliability over some years in withstanding high dynamic loads. At the same time, the demands of lightweight design and cost minimization are required by thought-out design, high-quality material, superior production quality and maintenance. In order to design a reliable and lightweight gearbox, it is necessary to analyze bearing rating life methods between standard and different bearing companies with calculation methods for modification factors. In this paper, the influence of life time of bearings will be pointed out. Bearing contact stress and load stress distribution of HEV gearbox are obtained and compared with Romaxdesigner and BearinX. And the unequal wear of the left bearing for the gearbox intermediate shaft is investigated between simulation and test.

• 한국기계가공학회지
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• 제11권4호
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• pp.25-30
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• 2012

The transportation is almost dependent on a single fuel petroleum with transportation energy dilemma. Hybrid Electric Vehicle(HEV) technology holds more advantages on efficiency improvements for petroleum consumption at the transportation. And bearing is recognized as the important component of gearbox. Gearboxes for HEV transmission have been ensured the highest reliability over some years in withstanding high dynamic loads. At the same time, the demands of lightweight design and cost minimization are required by thought-out design, high-quality material, superior production quality and maintenance. In order to design a reliable and lightweight gearbox, it is necessary to analyze bearing rating life methods between standard and different bearing companies with calculation methods for modification factors. In this paper, the influence of life time of bearings will be pointed out. Bearing contact stress and load stress distribution of HEV gearbox are obtained and compared with Romaxdesigner and BearinX. And the unequal wear of the left bearing for the gearbox intermediate shaft is investigated between simulation and test.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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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.

• 대한기계학회논문집A
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• 제32권12호
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• pp.1055-1062
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• 2008

Engineering materials have been studied and developed remarkably for a long time. But, few reports about marine propeller materials are presented. Recently, some researchers have studied the material strength of marine propellers. However, studies on parametric sensitivity and probabilistic distribution of fatigue life of propeller materials have not been made yet. In this study, a method to predict the probabilistic distributions of fatigue life of propeller materials is presented, and the influence of several parameters on the life distribution is discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.234-239
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• 2004

A study on the probabilistic methodology for the estimation of the remaining life of Pressurized pipelines containing active corrosion defects is presented. This reliability assessment is earned out using extream value distribution of the corroded defects instead of already published failure perssure moded like NG18 or ASME B31G. The failure probability of pipelines depends on the number of corroded defects. and it could be calculated directly as the area exceeded a defined L V(Limited Value of corrosion depth). The remaining life of pressurized pipelines can also be estimated by the PDF of extream value distribution as calculating the exceeded area with a defined failure probability.

• International Journal of Reliability and Applications
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• 제2권4호
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• pp.241-251
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• 2001

In this paper, optimal bum-in time to minimize the total mean cost, which is the sum of manufacturing cost with burn-in and cumulative warranty-related cost, is obtained. When the products with cumulative pro-rata warranty have high failure rate in the early period (infant mortality period), a burn-in procedure is adopted to eliminate early product failures. After burn-in, the posterior product life distribution and the warranty-related cost are dependent on burn-in time; long burn-in period may reduce the warranty-related cost, but it increases the manufacturing cost. The paper provides a methodology to obtain total mean cost under burn-in and cumulative pro-rata warranty. Property of the optimal burn-in time is analyzed, and numerical examples and sensitivity analysis are studied.

• Communications for Statistical Applications and Methods
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• 제24권1호
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• pp.29-41
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• 2017

The estimation problem of expected time to failure of units is studied in a discrete set up. A simple step-stress accelerated life testing is considered with a Type-I censored sample from geometric distribution that is a commonly used distribution to model the lifetime of a device in discrete case. Maximum likelihood estimators as well as the associated distributions are derived. Exact, approximate and bootstrap approaches construct confidence intervals that are compared via a simulation study. Optimal confidence intervals are suggested in view of the expected width and coverage probability criteria. An illustrative example is also presented to explain the results of the paper. Finally, some conclusions are stated.