• 대한기계학회논문집A
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• 제40권12호
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• pp.987-995
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• 2016

본 연구는 $ZrO_2$의 비커스 경도에 대한 쇼트 피닝 효과를 연구하였다. 쇼트의 크기는 ${\phi}180{\mu}m$와 ${\phi}300{\mu}m$를 사용하여 피닝하였다. 비커스경도는 압입하중 98 N과 294 N으로 측정하였다. 비커스 경도는 와이블 통계 해석을 수행하여, 볼 크기 및 압압 하중에 따르는 영향을 평가하였다. 척도 파라메터는 98 N 압입 하중 및 ${\phi}180{\mu}m$ 쇼트 볼에서 크게 나타났다. 형상 파라메터도 대체적으로 작은 쇼트 볼(180sp)이 크게 나타났다. 이것으로부터 SP처리에 의한 압축 잔류 응력은 $ZrO_2$의 기계적 성질의 향상에 좋은 방법이다.

• 대한기계학회논문집A
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• 제35권10호
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• pp.1281-1289
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• 2011

본 논문에서는 소형풍력발전시스템 블레이드 제작에 사용되는 복합재료의 피로수명 데이터에 대한 통계적 해석을 위하여 다양한 확률분포 모델의 적합성에 대한 연구를 수행하였다. 이를 위하여 삼축 유리섬유강화 복합재료를 대상으로 0$^{\circ}C$, 45$^{\circ}C$ 및 90$^{\circ}C$ 의 하중방향에 대한 인장시험을 실시하였다. 또한 상기의 하중방향에 대하여 4 수준의 피로응력준에서의 피로시험을 수행하였다. 이를 통하여 획득한 피로수명 데이터를 대상으로 1) 전체 적합성, 2) 끝단 적합성 및 3) 피로물리 일치성의 기준을 이용하여 2 모수 Weibull, 3 모수 Weibull, 정규 및 대수정규분포의 적합성을 평가하였다. 또한 피로수명의 분산에 대한 하중방향 및 피로응력의 영향 역시 검토하였다.

• Advances in concrete construction
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• 제9권5호
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• pp.469-478
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• 2020

This study aims to establish a new methodological framework for the evaluation of the evolution of the reliability of plain concrete for pavement vs number of cycles under flexural fatigue loading. According to the framework, a new method calculating the reliability was proposed through probability simulation in order to describe a random accumulation of fatigue damage, which combines reliability theory, one-to-one probability density functions transformation technique, cumulative fatigue damage theory and Weibull distribution theory. Then the statistical analysis of flexural fatigue performance of cement concrete tested was carried out utilizing Weibull distribution. Ultimately, the reliability for the tested cement concrete was obtained by the proposed method. Results indicate that the stochastic evolution behavior of concrete materials under fatigue loading can be captured by the established framework. The flexural fatigue life data of concrete at different stress levels is well described utilizing the two-parameter Weibull distribution. The evolution of reliability for concrete materials tested in this study develops by three stages and may corresponds to develop stages of cracking. The proposed method may also be available for the analysis of degradation behaviors under non-fatigue conditions.

• 대한조선학회논문집
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• 제58권3호
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• pp.137-143
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• 2021

In this study, the fracture strength of Flexible Secondary Barrier (FSB) composites was standardized by conducting a distribution analysis of the fracture probability, considering that the fracture strength of FSB composites such as glass fiber reinforced composites is relatively large. As the mechanical performance of FSB composites varies with the fiber direction, 20 replicate uniaxial tensile tests were performed for different temperatures ranging from the ambient to cryogenic conditions, considering the actual operating environment of liquefied natural gas. For the probability statistical analysis, the Weibull distribution analysis derived from the weakest link theory was used, considering the large variance in the fracture strength and brittle fracture behavior. The results of the Weibull distribution analysis were used to calculate the standard fracture strength of the FSB composites for different fiber directions. The findings can help ensure the reliability of the FSB mechanical properties in different fiber directions in the design of the secondary barrier and structural analyses.

• 대한기계학회논문집A
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• 제27권6호
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• pp.923-929
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• 2003

In this paper, an analysis of fatigue crack growth behavior from a statistical point of view has been carried out. Fatigue crack growth tests were conducted on sixteen pre-cracked compact tension (CT) specimens of the pressure vessel (SPV50) steel in controlled identical load and environmental conditions. The assessment of the statistical distribution of fatigue crack growth experimental data obtained from SPV50 steel was studied and also the correlation of the parameter C and m in the Paris-Erdogan law was discussed. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Weibull. The fatigue crack growth rate seems to follow the 3-parameter Weibull and the log-normal distribution. The coefficient of variation (COV) of fatigue crack growth life was observed to decrease as the crack grows. Fatigue crack growth rate data shows a normal distribution for both m and logC. A strong negative linear correlation exists between the coefficient C and the exponent m.

• Communications for Statistical Applications and Methods
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• 제29권6호
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• pp.665-677
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• 2022

This paper proposes a new estimation method based on the maximum product of spacings for estimating unknown parameters of the three-parameter Weibull distribution under a generalized Type-II progressive hybrid censoring scheme which guarantees a constant number of observations and an appropriate experiment duration. The proposed approach is appropriate for a situation where the maximum likelihood estimation is invalid, especially, when the shape parameter is less than unity. Furthermore, it presents the enhanced performance in terms of the bias through the Monte Carlo simulation. In particular, the superiority of this approach is revealed even under the condition where the maximum likelihood estimation satisfies the classical asymptotic properties. Finally, to illustrate the practical application of the proposed approach, the real data analysis is conducted, and the superiority of the proposed method is demonstrated through a simple goodness-of-fit test.

• 한국전기전자재료학회논문지
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• 제19권10호
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• pp.947-952
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• 2006

It has been confirmed that the inner defect of insulator and the perfect diagnosis for aging are closely related to safe electric power transmission system and that the detection of accident and diagnosis technique turn out to be very important issues. But perfect diagnosis is difficult because discharge pattern is irregular. Thus, we investigated discharge pattern using the new distribution statistical models with cross-inked polyethylene(XLPE) specimens. Voltage was applied to power frequency by step method, and calibration of discharge was set to 50 pC. After the voltage was applied, it measured the discharge occurring during 10s. We investigated discharge pattern using the K-means analysis and Weibull function. We also investigated variation of centroid and shape parameter due to variation of voltage. As a result of analyzing K-means, it was confirmed that cluster including many object numbers was formed by the presence of void. And result of Weibull distribution, it was confirmed that shape parameter of discharge varied from 1.28 to 1.62 in no void specimens, and that shape parameter of discharge number varied from 1.28 to 1.62. In the void, shape parameter of discharge varied from 5.66 to 6.43, and shape parameter of discharge number varied from 5.05 to 5.08.

• 대한기계학회논문집A
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• 제39권10호
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• pp.955-962
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• 2015

비커스 경도 시험은 모든 재료에 적용할 수 있으며, 경도 시험 중에서 가장 광범위하게 사용된다. 경도는 기계적 성질을 평가하는 하나의 확률변수로 볼 수 있다. 본 연구는 $ZrO_2$ 단상 세라믹스와 $TiO_2$ 첨가량에 따르는 $ZrO_2/SiC$ 복합 세라믹스의 굽힘강도와 비커스 경도의 통계적 성질을 조사하였다. 굽힘강도와 비커스 경도는 와이블 확률 분포를 잘 따랐다. 척도 및 형상 파라메터는 $ZrO_2$ 모재 세라믹스, $ZrO_2/SiC/TiO_2$ 모재 세라믹스 및 이들을 열처리한 세라믹스를 사용하여 평가하였다. 또한 압입하중의 증가에 따른 영향도 평가하였다.

• Journal of the Korean Statistical Society
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• 제30권3호
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• pp.467-480
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• 2001

This paper considers the use of local $\phi$-divergence measures between posterior distributions under classes of perturbations in order to investigate the inherent robustness of certain classes. The smaller value of the limiting local $\phi$-divergence implies more robustness for the prior or the likelihood. We consider the cases when the likelihood comes form the class of weighted distribution. Two kinds of perturbations are considered for the local sensitivity analysis. In addition, some numerical examples are considered which provide measures of robustness.

• 대한의용생체공학회:의공학회지
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• 제37권1호
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• pp.21-30
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• 2016

Weibull distribution with two parameters, shape (k) and scale (s) parameters are used to model the fatigue failure analysis due to periodic vortex shedding of the synovial fluid in knee joints. In order to determine the later parameter, a suitable statistical model is required for velocity distribution of synovial fluid flow. Hence, wide applicability of Weibull distribution in life testing and reliability analysis can be applied to describe the probability distribution of synovial fluid flow velocity. In this work, comparisons of three most widely used methods for estimating Weibull parameters are carried out; i.e. the least square estimation method (LSEM), maximum likelihood estimator (MLE) and the method of moment (MOM), to study fatigue failure of bone joint due to periodic vortex shedding of synovial fluid. The performances of these methods are compared through the analysis of computer generated synovial fluidflow velocity distribution in the physiological range. Significant values for the (k) and (s) parameters are obtained by comparing these methods. The criterions such as root mean square error (RMSE), coefficient of determination ($R^2$), maximum error between the cumulative distribution functions (CDFs) or Kolmogorov-Smirnov (K-S) and the chi square tests are used for the comparison of the suitability of these methods. The results show that maximum likelihood method performs well for most of the cases studied and hence recommended.