• 대한기계학회논문집A
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• 제25권10호
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• pp.1528-1534
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• 2001

In order to improve Leak-Be(ore-Break methodology, more precisely the crack growth evaluation, a round robin analysis was proposed by the CEA Saclay. The aim of this analysis was to evaluate the crack initiation life, penetration life and shape of through wall crack under cyclic bending loads. The proposed round robin analysis is composed of three main topic; fatigue crack initiation, crack propagation and crack penetration. This paper deals with the first topic, crack initiation in a notched pipe under four point bending. Both elastic-plastic finite element analysis and Neuber's rule were used to estimate the crack initiation life and the finite element models were verified by mesh-refinement, stress distribution and global deflection. In elastic-plastic finite element analysis, crack initiation life was determined by strain amplitude at the notch tip and strain-life curve of the material. In the analytical method, Neuber's rule with the consideration of load history and mean stress effect, was used for the life estimation. The effect of notch tip radius, strain range, cyclic hardening rule were examined in this study. When these results were compared with the experimental ones, the global deformation was a good agreement but the crack initiation cycle was higher than the experimental result.

• Journal of Welding and Joining
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• 제33권6호
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• pp.49-54
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• 2015

Welding process is of importance to assemble products or structures, but also the process is structural weakness due to stress concentration in welding joint. The fatigue design of welded joint requires time & labor consuming fatigue test because the fatigue life is various according to the depth of joint, joint type and load type etc. In fatigue design codes, they guide to classify welding joints with their shape( BS7608, IIW Documents) and provide fatigue assessment information. In terms of numerical method for fatigue analysis, it is also difficult to decide the stress peak in joint because of mesh sensitivity which means that stress value is varies with element type or size on stress concentration zone. Hot-spot method is used generally, but Battelle of United States proposed Master S-N Curve based on structural stresses converted by mechanical equilibrium theory. In this research, we extracted master S-N curve from Battelle's fatigue test DB including test data of various welding joints to apply on Non-Load-Carrying cruciform Joint. Comparing fatigue results between the case of using normal stress and case of structural stress cor the cruciform Joint, The suggested Battelle method showed successive results.

• Communications for Statistical Applications and Methods
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• 제6권3호
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• pp.901-908
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• 1999

Using the Transformed Lorenz curve which is introduced by Cho et al.(1999) we propose the test statistic for testing of normality that is very important test in statistical analysis and compare the proposed test statistic with the Shapiro and Wilk's W test statistic in terms of the power of test through by Monte Carlo method.

• 한국경영과학회지
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• 제10권1호
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• pp.65-78
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• 1985

In this paper, the approach getting a total demand by forecasting the new demand and the replacement demand separately and adding them is used for long term forecasting of durable goods. Cross country analysis using the income as an independent variable and S-shaped growth curve as a fitting model is developed as a method of forecasting new demand. To get the replacement demand the methods using the number of ownership and the replacement rate and the methods using the past demand and the distribution of the product life are proposed. And the theoretical explannation for product life cycle's diversity, which is the one of the major considerations in the long term forecasting, is attempted by the combination of the new demand and the replacement demand patterns. This is applicated the long term forecasting of Korean passenger cars.

• 대한전기학회논문지
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• 제40권3호
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• pp.250-257
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• 1991

In the analysis of the electric machine by finite element method, the primary current has been selected as a driving source. But the voltage is constant and the primary current varies according to the load condition in the pracdtical system. Therefore, in this paper, magnetic flux distribution, primary current, input effective power, power factor, efficiency and propulsion force of S.L.I.M. were calculated by the finite element method cnsidering the voltage as a driving source. Because the driving characteristics could not be measured in the S.L.I.M., voltage-current curve, 3-phase current curve, and propulsion force were measured at the starting and they were compared with theoretical values.

• 산업기술연구
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• 제1권
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• pp.39-45
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• 1981

The typical characteristic shape of the Koryo inlaid celadon Maebyong was reviewed and the symmetry of S curve was analyzed by the method of geometric basis. The contours of Maebyongs sampled were drawn and divided with geometric rectangular proportion. The analytical results showed the static and dynamic symmetric of the vase and the ratios of height and base of the rectangles established for the analysis of their shapes were almost 1:1, 1:${\sqrt{2}}$ and 3:5(known as the Golden Ratio). The excellent beauty of the curve was principally caused by the balanced and harmonius division of the proportional rectangles. The contour line was developed along with the logarithmic spiral modified and introduced lately into the shape of Yi dynasty's liquor bottle.

• Wind and Structures
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• 제13권1호
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• pp.1-20
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• 2010

The recommended factored design wind load effects for overhead lattice transmission line towers by codes and standards are evaluated based on the applicable wind load factor, gust response factor and design wind speed. The current factors and design wind speed were developed considering linear elastic responses and selected notional target safety levels. However, information on the nonlinear inelastic responses of such towers under extreme dynamic wind loading, and on the structural capacity curves of the towers in relation to the design capacities, is lacking. The knowledge and assessment of the capacity curve, and its relation to the design strength, is important to evaluate the integrity and reliability of these towers. Such an assessment was performed in the present study, using a nonlinear static pushover (NSP) analysis and incremental dynamic analysis (IDA), both of which are commonly used in earthquake engineering. For the IDA, temporal and spatially varying wind speeds are simulated based on power spectral density and coherence functions. Numerical results show that the structural capacity curves of the tower determined from the NSP analysis depend on the load pattern, and that the curves determined from the nonlinear static pushover analysis are similar to those obtained from IDA.

• 한국의류산업학회지
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• 제20권4호
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• pp.429-438
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• 2018

This study analyzed the fit-zone of the neck for females in their 60s. We considered the standard body types of females in their 60s and the four body types from the sixth Size Korea. The results of the study were as follows. We could not determine a pattern formula for the neck based on the changes in the body type of females in their 60s. However, the position of the lateral neck point generally showed a significant difference from that of females in their 20s. In the case of the shoulder angle, the point of the shoulder was angled slightly towards the back in all body types. It was also found that the curve of the neck circumference for both the collar and the bodice should have been smoother than what was shown on the 3D shape. The larger the height difference between the point of the back of the neck and the lateral neck point in the 3D shape, the smoother the design should be at the curve of the circumference at the front of the neck. A larger curvature in the front radius of the 3D shape increased the difference in the shape of the curve between the collar and the basic pattern of the bodice. Hence, a more careful design is required for these parts of the pattern. In addition, the more the front neck is bent, the smoother the circumference curve should be in the pattern design at the front of the neck and the collar.

• 항공우주기술
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• 제13권1호
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• pp.10-19
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• 2014

기존의 헬리콥터 로터 시스템에서 기계적 힌지/베어링 부품을 복합재 빔 구성품으로 대체하여 중량과 부품수를 줄인 무베어링 허브 시스템을 설계하였으며, 그 중 중요 구성품인 유연보와 토크튜브에 대한 피로 안전수명 해석을 수행하였다. VABS를 이용한 2차원 단면 해석 수행을 통해 인장, 굽힘 및 뒤틀림 강성을 도출하였으며 2차원 탄성 보 모델에 대한 단면 구조해석 방법을 적용하여 각 단면에 발생하는 변형율을 계산하였다. 각 복합재 소재에 대한 S-N 곡선을 Wohler equation을 적용하여 생성하였으며, 정적구조해석을 통해 피로파손에 취약할 것으로 판단되는 영역에 대한 피로해석을 수행하였다. 헬리콥터 운영시로부터 구성품에 발생하는 하중은 CAMRAD II를 통해 계산하였으며, 하중해석 결과를 HELIX/FELIX 표준 하중 스펙트럼에 적용하여 무베어링 로터 허브 시스템의 하중 스펙트럼을 생성한 후, 이를 통해 최종적으로 피로 안전수명을 산출하였다.

• Communications for Statistical Applications and Methods
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• 제19권3호
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• pp.433-450
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• 2012

연구자가 같은 작업을 반복적으로 수행할 때, 작업 효율성은 연구에 관련된 지식, 경험, 기술이 축적되면서 향상된다. 결과를 얻기 위해 연구에 투자하는 시간은 같은 작업을 반복함으로써 줄일 수 있다. 이러한 현상을 학습곡선 효과(learning curve effect)라고 일컫는다. 학습곡선(learning curves)은 학습의 변화를 시각적으로 나타낸 것으로 이전의 학습곡선 연구에서는 시간을 일정한 구간으로 나누어 구간별 작업에 대한 숙련도의 평균 차이 여부를 확인하였다. 이러한 방법은 구간을 어떻게 나눌 것인가 하는 기준이 존재하지 않으며, 더욱이 이항 반응 자료로 모형을 적합하기 어려운 문제점을 가지고 있다. 본 연구에서는 이산형 확률변수 중 이항 반응 자료(베르누이자료)에 대한 학습곡선의 통계적 모형에 초점을 맞추고자 한다. 누적확률분포의 특성을 이용하여 모수를 추정하기 위해서 뉴튼-랩슨 방법(Newton-Raphson method)을 사용하였고, 이 연구에서 제안한 모형의 점근적 분포를 구하였다.