• Title/Summary/Keyword: weibull distribution

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Statistical Distribution of Fatigue Life of Composite Materials for Small Wind-Turbine Blades (소형풍력발전 블레이드용 복합재료의 피로수명 분포에 대한 확률론적 평가)

  • Kang, Ki-Weon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.10
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    • pp.1281-1289
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    • 2011
  • This paper deals with several statistical distribution functions for the analysis of fatigue life data of composite laminates for small wind-turbine blades. A series of tensile tests was performed on triaxial glass/epoxy laminates for loading directions of $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$. Then, fatigue tests were carried out to determine the fatigue life at the aforementioned loading directions and the fatigue stresses at four levels. Two-parameter Weibull, three-parameter Weibull, normal, and log-normal distributions were used to fit the fatigue life data of the triaxial composite laminates. The three-parameter Weibull distribution most accurately described the fatigue life data measured experimentally for all the cases considered. Furthermore, the variation of fatigue life was simultaneously affected by the loading direction and fatigue stress level.

Analysis of flexural fatigue failure of concrete made with 100% coarse recycled and natural aggregates

  • Murali, G.;Indhumathi, T.;Karthikeyan, K.;Ramkumar, V.R.
    • Computers and Concrete
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    • v.21 no.3
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    • pp.291-298
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    • 2018
  • In this study, the flexural fatigue performance of concrete beams made with 100% Coarse Recycled Concrete Aggregates (RCA) and 100% Coarse Natural Aggregates (NA) were statistically commanded. For this purpose, the experimental fatigue test results of earlier researcher were investigated using two parameter Weibull distribution. The shape and scale parameters of Weibull distribution function was evaluated using seven numerical methods namely, Graphical method (GM), Least-Squares (LS) regression of Y on X, Least-Squares (LS) regression of X on Y, Empherical Method of Lysen (EML), Mean Standard Deviation Method (MSDM), Energy Pattern Factor Method (EPFM) and Method of Moments (MOM). The average of Weibull parameters was used to incorporate survival probability into stress (S)-fatigue life (N) relationships. Based on the Weibull theory, as single and double logarithm fatigue equations for RCA and NA under different survival probability were provided. The results revealed that, by considering 0.9 level survival probability, the theoretical stress level corresponding to a fatigue failure number equal to one million cycle, decreases by 8.77% (calculated using single-logarithm fatigue equation) and 6.62% (calculated using double logarithm fatigue equation) in RCA when compared to NA concrete.

Stability Analysis of the Ignition Coil using Partial Discharge (부분방전법을 이용한 점화코일의 안정도 해석)

  • Park, Hee-Doo;Kim, Tag-Yong;Shin, Hyun-Taek;Kim, Weon-Jong;Shin, Jong-Yeol;Hong, Jin-Woong
    • Journal of the Korean Society of Safety
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    • v.21 no.1 s.73
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    • pp.53-58
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    • 2006
  • This paper has been addressed on the discharge characteristics of the ignition coil by Weibull function. It analyzed discharge number and amount of discharge using Weibull distribution to know the inter-relationship between partial discharge and mileage. We detected the discharge which happens for 10 seconds. The applied voltage increased by 0.5[kV] at discharge inception voltage. We diagnosed failure rate using the shape parameters. As a result, we confirmed that the failure rate was increased, because the shape parameter showed the value of 5 according to increasing mileage degradation. Also, it is considered to increase the degradation of inner insulator of ignition coil. Because failure rate of virgin was increased from 0[%] to 25[%] after degradation, stability analysis of the ignition coil using Weibull analysis is possible.

Parameter Estimation and Analysis of Deepwater Design Wave in Marginal Seas around Korea (한국 연안 심해 설계파의 매개변수 추정 및 분석)

  • Kim, Jeong-Dae;Jeong, Shin-Taek;Cho, Hong-Yeon;Oh, Nam-Sun
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.19 no.4
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    • pp.313-319
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    • 2007
  • Long term wave climate of both extreme and operational wave height is essential for planning and designing coastal structures. Since the availability of the field wave data for the waters around Korean peninsula is limited to provide a reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. In this paper, a set of deep water wave data obtained from KORDI(2003) were analyzed for extreme wave heights. These wave data at 67 stations off the Korean coast from 1979 to 1998 were arranged in the 16 directions. The probability distributions considered in this research were the FT-I and Weibull distribution. For each of these distributions, the method proposed by Goda(2004) was applied to estimate the parameters. For judgment of best fitting, MIR criterion proposed by Goda and Gobune(1990) was used. FT-I distribution which best fits to the 886 data, while Weibull(k=0.75) 81 data, Weibull(k=1.00) 105 data.

Selecting probability distribution of event mean concentrations from paddy fields (논으로부터 배출되는 유량가중평균 수질농도의 적정 확률분포 선정)

  • Jung, Jaewoon;Choi, Dongho;Yoon, Kwangsik
    • Journal of Environmental Impact Assessment
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    • v.23 no.4
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    • pp.285-295
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    • 2014
  • In this study, we analyzed probability distribution of EMCs (Event Mean Concentration) of COD, TOC, T-N, T-P and SS from rice paddy fields and compared the mean values of observed EMCs and the median values of estimated EMCs ($EMC_{50}$) through probability distribution. The field monitoring was conducted during a period of four crop-years (from May 1, 2008, to September 30. 2011) in a rice cultivation area located in Emda-myun, Hampyeong gun, Jeollanam-do, Korea. Four probability distributions such as Normal, Log-normal, Gamma, and Weibull distribution were used to fit values of EMCs from rice paddy fields. Our results showed that the applicable probability distributions were Normal, Log-normal, and Gamma distribution for COD, and Normal, Log- Normal, Gamma and Weibull distribution for T-N, and Log-normal, Gamma and Weibull distribution for T-P and TOC, and Log-normal and Gamma distribution for SS. Log-normal and Gamma distributions were acceptable for EMCs of all water quality constituents(COD, TOC, T-N, T-P and SS). Meanwhile, mean value of observed COD was similar to median value estimated by the gamma distribution, and TOC, T-N, T-P, and SS were similar to median value estimated by log-normal distribution, respectively.

The new odd-burr rayleigh distribution for wind speed characterization

  • Arik, Ibrahim;Kantar, Yeliz M.;Usta, Ilhan
    • Wind and Structures
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    • v.28 no.6
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    • pp.369-380
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    • 2019
  • Statistical distributions are very useful in describing wind speed characteristics and in predicting wind power potential of a specified region. Although the Weibull distribution is the most popular one in wind energy literature, it does not seem to be able to perfectly fit all the investigated wind speed data in nature. Thus, many studies are still being conducted to find flexible distribution for modelling wind speed data. In this study, we propose a new Odd-Burr Rayleigh distribution for wind speed characterization. The Odd-Burr Rayleigh distribution with two shape parameters is flexible enough to model different shapes of wind speed data and thus it can be an alternative wind speed distribution for the assessment of wind energy potential. Therefore, suitability of the Odd-Burr Rayleigh distribution is investigated on real wind speed data taken from different regions in the South Africa. Numerical results of the conducted analysis confirm that the new Odd-Burr Rayleigh distribution is suitable for modelling most of the considered real wind speed cases and it also can be used for predicting wind power.

Probabilistic Characteristics of Fatigue Behavior Parameter of Paris-Erdogan Law in Mg-Al-Zn Alloy (Mg-Al-Zn 합금의 Paris-Erdogan 법칙에 따른 피로거동 파라미터의 확률론적 특성)

  • Choi, Seon-Soon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.4
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    • pp.375-381
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    • 2011
  • The primary aim of this study is to investigate the probabilistic characteristics of the fatigue parameters that describe the fatigue crack growth behavior in magnesium alloy. Statistical fatigue crack propagation experiments have been performed on rolled AZ31 magnesium alloy CT specimens with different specimen thickness, load ratio, and maximum load at ambient temperature in a laboratory. Using the statistical fatigue data obtained from these experiments, the goodness-of-fit of the probability distribution of the fatigue behavior parameters is evaluated in this study by performing statistical analyses. The crack growth rate coefficient is a fatigue parameter having a very large COV(Coefficient of Variation), but the variation of a crack growth rate exponent is not substantial. It is considered that a crack growth rate exponent can be a material constant. It is also found that the best fit probability distribution of the parameters such as the crack growth rate coefficient and crack growth rate exponent for a magnesium alloy is a three-parameter Weibull distribution, and two-parameter Weibull distribution is a good distribution only for the crack growth rate coefficient.

Reliability Analysis for Power Plants Based on Insufficient Failure Data (불충분한 고장 데이터에 기초한 발전소의 신뢰도 산정기법에 관한 연구)

  • 이승철;최동수
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.52 no.7
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    • pp.401-406
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    • 2003
  • Electric power industries in several countries are currently undergoing major changes, mainly represented by the privatizations of the power plants and distribution systems. Reliable operations of the power plants directly contribute to the revenue increases of the generation companies in such competitive environments. Strategic optimizations should be performed between the levels of the reliabilities to be maintained and the various preventive maintenance costs, which require the accurate estimations of the power plant reliabilities. However, accurate estimations of the power plant reliabilities are often limited by the lack of accurate power plant failure data. A power plant is not supposed to be failed that often. And if it fails, its impact upon the power system stability is quite substantial in most cases, setting aside the significant revenue losses and lowered company images. Reliability assessment is also important for Independent System Operators(ISO) or Market Operators to properly assess the level of needed compensations for the installed capacity based on the availability of the generation plants. In this paper, we present a power plant reliability estimation technique that can be applied when the failure data is insufficient. Median rank and Weibull distribution are used to accommodate such insufficiency. The Median rank is utilized to derive the cumulative failure probability for each ordered failure. The Weibull distribution is used because of its flexibility of accommodating several different distribution types based on the shape parameter values. The proposed method is applied to small size failure data and its application potential is demonstrated.

Statistical Properties of Vickers Hardness of Post Weld Heat Treated Friction Welded Parts in Alloy718 (Alloy718 마찰용접 후열처리재의 비커스 경도의 통계적 성질)

  • Kong, Yu-Sik;Kwon, Hyeok-Yong;Kim, Seon-Jin
    • Journal of Ocean Engineering and Technology
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    • v.23 no.6
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    • pp.105-110
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    • 2009
  • The objective of this paper is to investigate the statistical properties of Vickers hardness (HV) for friction welded parts in a Ni-based super alloy (Alloy718). In the case of post weld heat treatment (PWHT) parts, hardness tests were repeated for three different applied loads, 100, 200, and 300 g, with a duration time of 10 seconds. The arithmetic means of the Vickers hardness in heat affected zone (HAZ) materials were smaller than those of the base metal (BM) in all of the applied loads. The coefficient of variation (COV) for the BM and HAZ decreased by increasing the applied load. The probability distribution of the Vickers hardness followed the Weibull distribution well. The distribution of the Vickers hardness was not found to be symmetric. The shape parameter and scale parameter increased by increasing the applied load at both the BM and HAZ.

Assessment of Wind Energy Potentiality in Wolryong using Short-term Observation (단기관측에 의한 월령 연안지역 풍력에너지 잠재량 평가)

  • Jeong, Tae-Yoon;Lim, Hee-Chang
    • New & Renewable Energy
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    • v.5 no.4
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    • pp.11-18
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    • 2009
  • Wind energy resources are recently considered as an important power generation alternative in the future. The fact that the investment of wind turbine installation continues to increase has motivated a need to develop more widely applicable methodologies for evaluating the actual benefits of adding wind turbines to conventional generating systems. This study is aiming to estimate the future wind resources with various estimation methods. The wind power is calculated at the hub height 75m of 800KW and 1,500KW wind turbines in Wolryong site, Jeju island, South Korea. Three equations - logarithmic, profile, and power law methods are applied for the accurate prediction of wind profile. In addition, yearly wind power can be calculated by using Weibull & Rayleigh distribution. It is found that predicted wind speed is highly affected by friction velocity, atmospheric stability, and averaged roughness length. It is concluded that Rayleigh distribution provides greater power generation than the Weibull distribution, especially for low wind-speed condition.

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