• Title/Summary/Keyword: weibull distribution

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확률분포를 이용한 복합재료의 강도예측 (Prediction of Laminate Composite Strength Using Probabilistic Approach)

  • 조영준;강태진;이경우
    • Composites Research
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    • 제13권1호
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    • pp.33-39
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    • 2000
  • 복합재료 적층판의 최종강도를 점증적 파손 해석방법을 사용하여 예측하였다. 플라이 강도를 확률분포로 가정했을 경우와 상수로 가정했을 경우 각각의 최종강도를 예측하였다. 복합재료의 강도에 대한 확률분포인 Weibull 분포를 이용하여 임의의 강도 값을 얻은 후 이 값을 Tsai-Hill 파손식에 대입하여 파손여부를 판정하고 파손이 일어나면 재료의 물성을 떨어뜨렸다. 이 방법에 의해서 얻어진 결과를 플라이의 강도를 상수로 가정하여 해석한 경우와의 차이에 대하여 고찰하였다. 결과적으로 두 경우 모두 실험치와 약간의 오차를 보였지만 파손의 경향성에 있어서는 확률분포를 이용한 강도해석이 실험값과 더 근사한 결과를 보였다.

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Slitting Knife의 손상에 미치는 마모의 영향 (The effect of wear on the damage of slitting knife)

  • 남기우;김철수;안석환
    • 동력기계공학회지
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    • 제20권4호
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    • pp.5-11
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    • 2016
  • This study analyzed the damage to a slitting knife after cutting steel sheets. Damages to the structure were observed and wear tests were conducted. In addition, the degradation on the damaged and undamaged parts was compared with a micro Vickers hardness test. Weibull statistical analysis was carried out in order to evaluate the reliability of the micro Vickers hardness measured data. Spalling of the edge portion occurred by degradation during use over a long period. Rough parts in the specimens were caused by damage because the slitting knife was used for 1 year. The friction coefficient and wear loss at the damaged parts of the knife edge were slightly larger from shock due to repetitive cutting operation. The micro Vickers hardness followed a two-parameter Weibull probability distribution.

Design of Step-Stress Accelerated Life Tests for Weibull Distributions with a Nonconstant Shape Parameter

  • Kim, C. M.;D. S. Bai
    • Journal of the Korean Statistical Society
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    • 제28권4호
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    • pp.415-433
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    • 1999
  • This paper considers the design of step-stress accelerated life tests for the Weibull distribution with a nonconstant shape parameter under Type I censoring. It is assumed that scale and shape parameters are log-linear functions of (possibly transformed) stress and that a cumulative exposure model holds for the effect of changing stress. The asymptotic variance of the maximum likelihood estimator of a stated quantile at design stress is used as an optimality criterion. The optimum three step-stress plans are presented for selected values of design parameters and the effects of errors in pre- estimates of the design parameters are investigated.

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임의 중단모형에서 최소제곱법을 이용한 와이블분포의 모수 추정 (An Estimation of Parameters in Weibull Distribution Using Least Squares Method under Random Censoring Model)

  • 이우동
    • Journal of the Korean Data and Information Science Society
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    • 제7권2호
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    • pp.263-272
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    • 1996
  • 임의의 기계에 대한 수명의 분포는 와이블분포를 하는 경우가 흔하다. 그리고 현실적으로 기계의 수명시간을 검정할 때, 시험시간및 여러 환경적인 제약에 의하여 표본으로 주어진 기계의 수명을 모두 관측하기는 어렵다. 그래서, 본 연구에서는 임의 중단모형 하에서 와이블분포의 모수를 최소제곱법(least squares method)을 이용하여 추정하고 기존의 최대우도추정량(maximum likelihood estimates)과 효율성의 측면에서 비교하고자 한다.

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흡습된 CFRP의 AE에 의한 파과거동과 신뢰성 평가 (Fracture behavior using AE method and reliability assessment of CFRP based on absorbed moisture)

  • 남기우;김선진
    • 한국해양공학회지
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    • 제10권4호
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    • pp.38-50
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    • 1996
  • Recently carbon fiber reinforced plastic (CFRP) has been used structural materials in corrosive environment such as for water, chemical tank and pipes. However, mechanical properties of such materials may be change when CFRP and exposed to corrosive environment for long periods of time. The degradation behavior of carbon fiber/epoxy resin composite material in distilled water is investigated using acoustic emission (AE) technique, Fracture toughness tests are performed on the compact tension specimens that are pilled by two types of $[O_2/9O_2]_{3s}$ and $[O/9O]_6s$. During the testes, AE test was carried out to monitor the damage of CFRP by moisture absorption. The data was treated by 2-parameter Weibull distribution and the fracture surface was observed by scanning electron microscope.

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STS304강의 순수 및 외팔보형 굽힘 피로에 대한 파괴확률 특성 (Fracture Probability Properties of Pure and Cantilever Bending Fatigue of STS304 Steel)

  • 노성국;박대현;정순억
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.199-204
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    • 2001
  • Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frenquently. Therefore many people are suffering harm of property. The destruction cause of macaine components is almost accused by fatigue. This study is test for STS304 specimen using pure and cantilever bending state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed.

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The Analysis of Discharge Distribution due to the Inner Void of Extra High Voltage Cable

  • Kim Tag-Yong;Hong Jin-Woong
    • KIEE International Transactions on Electrophysics and Applications
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    • 제5C권4호
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    • pp.155-160
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    • 2005
  • This paper addresses the discharge characteristics of cross-linked polyethylene according to void by the Weibull function. It analyzes discharge number and amount of discharge using Weibull distribution to identify the inter-relationship between partial discharge and defect. We detected a 10 second discharge. The applied voltage increased by 1 [kV] at discharge inception voltage. As a result, in a no-void specimen, the shape parameter was consistent according to the increase of voltage, whereas, in a void specimen, it increased according to the increase of voltage. As the result, the shape parameter expressed a fixed value at no-void specimen. However, in void specimen, according to increasing voltage shape parameter rapidly increases.

Reliability over time of wind turbines steel towers subjected to fatigue

  • Berny-Brandt, Emilio A.;Ruiz, Sonia E.
    • Wind and Structures
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    • 제23권1호
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    • pp.75-90
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    • 2016
  • A probabilistic approach that combines structural demand hazard analysis with cumulative damage assessment is presented and applied to a steel tower of a wind turbine. The study presents the step by step procedure to compare the reliability over time of the structure subjected to fatigue, assuming: a) a binomial Weibull annual wind speed, and b) a traditional Weibull probability distribution function (PDF). The probabilistic analysis involves the calculation of force time simulated histories, fatigue analysis at the steel tower base, wind hazard curves and structural fragility curves. Differences in the structural reliability over time depending on the wind speed PDF assumed are found, and recommendations about selecting a real PDF are given.

일수문량의 RUN-LENGTH 및 RUN-SUM의 SIMULATION (Simulation of Run-Length and Run-Sum of Daily Rainfall and Streamflow)

  • 이순택;지홍기
    • 물과 미래
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    • 제10권1호
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    • pp.79-94
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    • 1977
  • 본 연구는 Run-Length와 Run-Sum에 의한 강우량과 하천유량을 분석하여 그 특성을 구명하고, 이로부터 모의발생 모델(Simulation Model)을 설정하여 검토하는데 목적을 두고 있다. 분석에 있어서는 우리나라의 주요도시(서울, 대구 및 부산)의 일강우량과 주요하천(한강, 낙동강 및 금강)의 일류량 자료들을 사용하였다. 또한 해석에 있어서는 Run-Length와 Run-Sum에 대한 각각의 분포형 분석으로부터 Weibull 분포 및 1-변수지수 분포를 하고 있음을 알았으며, 이로부터 Monte Carlo 기법(Monte Carlo technique)을 기초로 하는 Weibull모델(Weibull model)과 1-변수지수 모델(One-Parameter Exponential Model)에 의해서 Run-Length와 Run-Sum을 모의발생 시켰다. 그 결과 기록치(Historical Data)에 근사한 모의발생 자료(Simulation Data)를 얻었다.

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크리프 파단 데이터의 변동성에 대한 새로운 고찰과 수명예측 (New Considerations on Variability of Creep Rupture Data and Life Prediction)

  • 정원택;공유식;김선진
    • 대한기계학회논문집A
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    • 제33권10호
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    • pp.1119-1124
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    • 2009
  • This paper deals with the variability analysis of short term creep rupture test data based on the previous creep rupture tests and the possibility of the creep life prediction. From creep tests performed by constant uniaxial stresses at 600, 650 and $700^{\circ}C$ elevated temperature, in order to investigate the variability of short-term creep rupture data, the creep curves were analyzed for normalized creep strain divided by initial strain. There are some variability in the creep rupture data. And, the difference between general creep curves and normalized creep curves were obtained. The effects of the creep rupture time (RT) and steady state creep rate (SSCR) on the Weibull distribution parameters were investigated. There were good relation between normal Weibull parameters and normalized Weibull parameters. Finally, the predicted creep life were compared with the Monkman-Grant model.