• Composites Research
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• v.16 no.6
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• pp.1-9
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• 2003

In this paper, probabilistic failure analysis based on Weibull distribution function is proposed to predict the fiber strength of composite pressure vessel. And, experimental tests were performed using fiber strand specimens, unidirectional laminate specimens and composite pressure vessels to confirm the volumetric size effect on the fiber strength. As an analytical method, the Weibull weakest link model and the sequential multi-step failure model are considered and mutually compared. The volumetric size effect shows the clearly observed tendency towards fiber strength degradation with increasing stressed volume. Good agreement of fiber strength distribution was shown between test data and predicted results for unidirectional laminate and hoop ply in pressure vessel. The site effect on fiber strength depends on material and processing factors, the reduction of fiber strength due to the stressed volume shows different values according to the variation of material and processing conditions.

• Journal of the Korean Wood Science and Technology
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• v.31 no.5
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• pp.72-79
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• 2003

In reliability based design(RBD) method, the distribution characteristics of mechanical properties of material are basic input variable. Therefore, distribution type and parameters of mechanical properties should be determined accurately. Until now, the properties were derived from tests with small, clear specimens. However, the test conditions should emulate as nearly as possible the way in which the timber would be used in practice and the test results should, as closely as possible, reflect the structural end use conditions to which the timber products would be subjected. In this study, structural timbers (38mm by 140mm, 3.0m long) were graded by visual assessment of growth characteristics and defects. And then bending tests were conducted on 498 structural size timbers. For each grade, the distribution type and the parameters of mechanical properties were determined for each grade. For the determination of best-fit distribution type, comparing of square error between distribution types and KS test were conducted. Best-fit distribution type of bending strength(MOR) is weibull distribution for all grade. In case of MOE, normal distribution is best-fit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.2004-2010
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• 2003

Fracture life and crack retardation behavior were examined experimentally using CT specimens of aluminum alloy 5083. Crack retardation life and fracture life were a wide difference. between 0.8 and 0.6 in proportion to ratio of load reduction. The wheeler model retardation parameter was used successfully to predict crack growth behavior. By using a crack propagation rule, prediction of fracture life can be evaluated quantitatively. A statistical approach based on Weibull distribution was applied to the test data to evaluate the dispersion in the retardation life and fracture life by the change of load reduction.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.435-438
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• 2009

Wind speed is measured on the nacelle at the location of wind turbines are installed. The wind speed is transformed to inlet wind speed at the front of hub using newly developed algorithm derived from energy conservation. Wind energy potential is analyzed using the inlet air velocity in the region of Bieung-do wind farm. As results, wind speed depending on the month, yearly averaged wind speed, wind speed distribution, and energy density are showed in this study. Bieung-do area is close to Saemankeum, and the analysis of wind energy potential in Bieung area will be helpful to understand and develop wind energy industry in Saemankeum area.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.200-206
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• 1992

The effect of fiber diameter and gauge length on pull-out test for the interfacial properties in fiber reinforced resin composites have been investigated and these results have been arranged as statistical analysis. The fiber and matrix resins used for this study were stainless steel fiber (SUS316) and carbon fiber (high strength type), epoxy and high density polyethylene resin. From this study, it has been found that shear strength are constant regardless of gauge length of pull-out test and coefficient of variation depend on fiber diameter. In addition, it has been found that the interfacial shear strength decreased with the increasing fiber diameter, and in all case, Weibull parameter (m) has approximately 1.2/C.O.V.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.81-84
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• 2008

This paper discussed the validity of wind force power generation in consideration of the topographical characteristics of Korea. In order to estimate the exact generation of wind power plants, we analyzed and compared wind resources in mountain areas and plain areas by introducing not only wind velocity, the most important variable, but also wind distribution and wind standard deviation that can reflect the influence of landform sufficiently. According to the results of this study, generation was higher at wind power plants installed in southwestern coastal areas where wind velocity was low than at those installed in mountain areas in Gangwondo where wind velocity was high. This suggests that the shape parameter of wind distribution is low due to the characteristics of mountain areas. and the standard deviation of wind velocity is large due to the effect of mountain winds, and therefore, actual generation is low in mountain areas although wind velocity is high.

• Journal of the Korean Solar Energy Society
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• v.28 no.6
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• pp.24-32
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• 2008

This paper discussed the Feasibility study of wind power generation considering the topographical characteristics of Korea. In order to estimate the exact generation of wind power plants, we analyzed and compared wind resources in mountain areas and plain areas by introducing not only wind speed, the most important variable, but also wind distribution and wind standard deviation that can reflect the influence of landform sufficiently. According to the results of this study, generation was almost the same at wind power plants installed in southwestern coastal areas where wind speed was low as at those installed in mountain areas in Gangwondo where wind speed was high. This demonstrates that the shape parameter of wind distribution is low due to the characteristics of mountain areas, and the standard deviation of wind speed is large due to the effect of mountain winds, therefore, actual generation compared to southwestern coastal areas is almost similar in mountain areas even though wind speed is high.

• Journal of the Korean Solar Energy Society
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• v.30 no.2
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• pp.54-64
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• 2010

Interest in new and renewable energies like solar energy and wind energy is increasing throughout the world due to the rapidly expanding energy consumption and environmental reasons. An essential requirement for wind force power generation is estimating the size of wind energy accurately. Wind energy is estimated usually using meteorological data or field measurement. This study attempted to estimate wind energy density using meteorological data on daily mean wind speed and the Weibull parameters in Seoul, a representative inland city where over 60% of 15 story or higher apartments in Korea are situated, and Busan, Incheon, Ulsan and Jeju that are major coastal cities in Korea. According to the results of analysis, the monthly mean probability density distribution based on the daily mean wind speed agreed well with the monthly mean probability density distribution based on the Weibull parameters. This finding suggests that the Weibull parameters, which is highly applicable and convenient, can be utilized to estimate the wind energy density distribution of each area. Another finding was that wind energy density was higher in coastal cities Busan and Incheon than in inland city Seoul.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.58-64
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• 1998

An analysis method for the reliability of ceramic structures subjected to thermal shocks is presented. Flaws with the size of given probability distribution function are assumed to be distributed at random with a certain density per unit volume in the structures. Criterions for crack instability are derived for brittle solids under general thermal stresses. A probabilistic failure model is presented to study the probability of crack instability for brittle solids containing cracks with uncertain size. The reliabilities of brittle structures are evaluated based on the weakest-link hypothesis, which states that a structure fails when the cracks in any differential volume become unstable. A numerical example is given to demonstrate the application of the proposed method.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.21-24
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• 2005

This study explains the procedure that should be taken to develop a successful wind park project. It Provide guideline for activities and studies to be done step by step solution. This study follow a chronological flow through the development process. They cover Technical consideration, Assessment of Wind Energy Resource, Wind park siting and Energy yield calculation. It's build on the experience gained by the Youngduk Wind Park project and give the playa role in the development of wind energy projects. It is important to understand all theses issues if a new project is to be successfully completed.