• Title, Summary, Keyword: Fatigue life distribution

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Analysis on fatigue life distribution of composite materials (복합재료 피로 수명 분포에 관한 고찰)

  • 황운봉;한경섭
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.4
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    • pp.790-805
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    • 1988
  • Static strength and fatigue life scattering of glass fiber reinforced epoxy composite materials has been studied. Normal, lognormal, two-parameter and three-parameter Weibull distribution functions are used for strength and one-stress fatigue life distribution. The value of mean fatigue life is analysed using mean fatigue life, mean log fatigue life and expected value of 2 and 3-parameter Weibull distribution functions. Modification on non-statistical cumulative damage models is made in order to interpret the result of two-stress level fatigue life scattering. The comparison results show that 3-parameter Weibull distribution has better predictions in static strength and one-stress level fatigue life distributions. However, no advantage of 3-parameter Weibll distribution is found over 2-parameter Weibull distribution in two-stress level fatigue life predictions. It is found that two-stress level fatigue life prediction by the expanded equal rank assumption is close to the experimental data.

Characteristics of Fatigue Life Distribution for Carbon/Epoxy Composite Laminates (탄소섬유/에폭시 복합적층판의 피로수명 분포특성)

  • 김영기;박병준;김재훈;이영신;전제춘
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.119-123
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    • 2000
  • The characteristics of fatigue life distribution for Carbon/epoxy composite laminates was investigated under tension-tension loading(R=0.1). The statistical nature of the fatigue life of the composite materials was analyzed by Weibull, normal, lognormal distributions As a result, it was observed that the correlation between the experimental results and the theoretical predictions for the fatigue life is good. The distribution of the static ultimate strength has the characteristic of lognormal distribution and distribution of the fatigue life has characteristics of the weibull distribution.

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The Probability Distribution of Fatigue Crack Propagation Life Considering Effect of Crack Coalescence (균열의 합체를 고려한 피로균열 진전수명의 확률분포)

  • Bang, Hong-In;Yun, Han-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.5
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    • pp.1281-1287
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    • 2000
  • The studies of probability distribution of the fatigue crack growth life have been somewhat reported. But the study on the probability distribution of the fatigue crack growth life considering the crack coalescence for three dimensional surface fatigue crack has apparently not been reported to date. In this study, the computer program has been developed to predict the probability distribution of the fatigue crack growth life considering the crack coalescence. The effects of parameters for the distribution of the fatigue crack propagation life were evaluated by using the program.

Estimation of Probability Distribution Fit for Fatigue Crack Propagation Life of AZ31 Magnesium Alloy (AZ31 마그네슘합금의 피로균열진전수명에 적합한 확률분포 평가)

  • Choi, Seon-Soon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.8
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    • pp.707-719
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    • 2009
  • The variables relating to the fatigue behavior have uncertainty and are random. The fatigue crack propagation is, thus, stochastic in nature. In this study, fatigue experiments are performed on the specimen of the magnesium alloy AZ31. The data of the fatigue life are scattered even in the same experimental condition. It is necessary to determine the probability distribution of the fatigue crack propagation life for the reliability analysis as well as the design and maintenance of structural components. Therefore the statistics and the probability distribution for the fatigue crack propagation life are investigated and the best fit probability distribution of that is proposed in this paper.

Effect of Boundary Conditions on Reliability and Cumulative Distribution Characteristics of Fatigue Failure Life in Magnesium Alloy (마그네슘합금의 피로파손수명의 누적확률분포특성과 신뢰성에 미치는 경계조건의 영향)

  • Choi, Seon-Soon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.2
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    • pp.594-599
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    • 2011
  • In this paper, the effect of the boundary conditions on the reliability and the cumulative distribution characteristics of the fatigue failure life is analyzed in a magnesium alloy AZ31. The boundary conditions are specimen thickness, stress ratio, and maximum fatigue load. The statistical data of the fatigue failure life are obtained by fatigue crack propagation tests under the detail conditions for each boundary condition. The 3-parameter Weibull distribution is used to analyze a statistical characteristics of the fatigue failure life in magnesium alloy AZ31. It is found that the statistical fatigue failure life is long in the case of a thicker specimen, a larger stress ratio, and a smaller maximum fatigue load. Under the opposite cases, the reliability on the fatigue failure life is rapidly dropped.

Deriving a Probabilistic Model for Fatigue Life Based on Physical Failure Mechanism

  • Suneung Ahn
    • Journal of the Society of Korea Industrial and Systems Engineering
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    • v.24 no.68
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    • pp.1-7
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    • 2001
  • A probabilistic model for fatigue life of a structural component is derived when the component is in a variable-amplitude loading environment. The physical mechanism which governs fatigue failure is used to model the fatigue life. Especially, the judgement of rotational symmetry in the-stress-intensity-factors results in the probability distribution for fatigue life. The probability distribution is related to the familiar truncated Gaussian distribution, which has a single parameter with a direct physical meaning.

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Estimation of Probability Distribution of Fatigue Lives in Crank Throw Forged Steel (크랭크스로 단조강의 피로수명의 확률분포 추정)

  • Kim, Seon-Jin;Ahn, Seok-Hwan
    • Journal of Power System Engineering
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    • v.20 no.3
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    • pp.29-35
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    • 2016
  • Because of the severe service environment of the large marine vessel, the fatigue strength and its evaluation play an important role in design and maintenance of marine crankshaft. The aim of this work is to investigate the probability distribution of fatigue lives in crank throw forged steel and to develop the methodology for estimation of the probabilistic design fatigue strength. Detailed studies were performed on the constant amplitude axial loading fatigue test. The experiments were controlled by stress ratio of -1 and 15Hz frequency for each stress level. The considerable variability of fatigue life was observed in each stress level under rigidly controlled constant fatigue testing conditions. The fatigue life of crank throw forged steel was well followed the log-normal and Weibull distribution. In addition, it can be used for the estimation of probabilistic design fatigue strength by using the proposed methodology.

A Statistical Analysis on Fatigue Life Distribution in Spheroidal Graphite Cast Iron (구상흑연주철의 피로수명분포에 대한 통계적 해석)

  • Jang, Seong-Su;Kim, Sang-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.9
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    • pp.2353-2360
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    • 2000
  • Statistical fatigue properties of metallic materials are increasingly required for reliability design purpose. In this study, static and fatigue tests were conducted and the normal, log-normal, two -parameter Weibull distributions at the 5% significance level are compared using the Kolmogorov-Smirnov goodness-of-fit test. Parameter estimation were compared with experimental results using the maximum likelihood method and least square method. It is found that two-parameter Weibull distribution and maximum likelihood method provide a good fit for static and fatigue life data. Therefore, it is applicable to the static and fatigue life analysis of the spheroidal graphite cast iron. The P-S-N curves were evaluated using log-normal distribution, which showed fatigue life behavior very well.

Prediction of Fatigue Design Life in Magnesium Alloy by Failure Probability (파손확률에 따른 마그네슘합금의 피로설계수명 예측)

  • Choi, Seon-Soon
    • 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.

Prediction of the Fatigue Life of Deep Groove Ball Bearing Under Radial and Moment Loads - Fatigue Life Tests and Proposal of the Life Adjustment Factors (반경방향과 모멘트하중 하에서의 깊은홈 베어링의 피로수명평가 - 수명시험 및 수명보정계수 제안)

  • 김완두;한동철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.12
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    • pp.3149-3158
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    • 1994
  • In this paper, using the formulation of dynamic equivalent load considering the effects of moment load and the equation to estimate the cage rotational speed, the new life equation of deep groove ball bearing under radial and moment loads was proposed. Fatigue life test apparatus with the measuring equipment of shaft and cage speed was designed and developed to be capable of subjecting combined radial and moment load. Fatigue life tests were executed by sudden death test method and the reliability of fatigue lives was evaluated by Weibull distribution analysis. From the results of fatigue tests and analysis, the relationships between film parameters and life adjustment factors were acquired. And it was turned out that so as to estimate the effect of moment load on fatigue life, the life adjustment factor as well as the dynamic equivalent load must be taken into account.