• International Journal of Aeronautical and Space Sciences
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• 제1권2호
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• pp.9-16
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• 2000

For aerodynamic design of missile bodies of non-circular cross-section, the combination of the slender body theory and the cross-flow analogy can hardly be applied owing to the lack of experimental data. An alternative is to utilize the Euler solution in the design stage. For enhanced accuracy, however, an adequate viscous correction is necessary to the Euler solution. In this work, such a procedure is examined to compensate the viscous effect by utilizing the concept of proportionality factor in cross-flow analogy. Predictions of aerodynamic coefficients combining the Euler solution and the viscous correction via proportionality factor are made for a missile body of elliptic cross-section. Results indicate that the present approach can be adopted in designing missile bodies of non-circular cross-sections.

• Steel and Composite Structures
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• 제18권4호
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• pp.985-1000
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• 2015

The method of cross-section analysis for different sections in a structural frame has been widely investigated since the 1960s for determination of sectional capacities of beam-columns. Many hand-calculated equations and design graphs were proposed for the specific shape and type of sections in pre-computer age decades ago. In design of many practical sections, these equations may be uneconomical and inapplicable for sections with irregular shapes, leading to the high construction cost or inadequate safety. This paper not only proposes a versatile numerical procedure for sectional analysis of beam-columns, but also suggests a method to account for residual stress and geometric imperfections separately and the approach is applied to design of high strength steels requiring axial force-moment interaction for advanced analysis or direct analysis. A cross-section analysis technique that provides interaction curves of arbitrary welded sections with consideration of the effects of residual stress by meshing the entire section into small triangular fibers is formulated. In this study, two doubly symmetric sections (box-section and H-section) fabricated by high-strength steel is utilized to validate the accuracy and efficiency of the proposed method against a hand-calculation procedure. The effects of residual stress are mostly not considered explicitly in previous works and they are considered in an explicit manner in this paper which further discusses the basis of the yield surface theory for design of structures made of high strength steels.

• 한국항공우주학회지
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• 제41권4호
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• pp.275-283
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• 2013

본 논문에서는 유전자 알고리즘을 이용한 복합재 로터 블레이드 단면 구조 최적설계방법에 대한 연구를 수행하였다. 반복적인 최적설계 계산을 위해 자동격자생성 프로그램을 개발하였으며, VABS를 이용해 로터 블레이드 단면에 대한 응력해석을 수행하였다. 로터 블레이드 최소질량을 목적함수로 정의하였으며, 응력 파손지수와 단면 질량중심 그리고 단위 길이 당 블레이드 최소질량을 구속조건으로 설정하였다. 최종적으로 본 논문의 복합재 로터 블레이드 단면 구조 최적설계방법을 통해서 스킨 적층각 및 스킨 두께 그리고 토션박스 두께, 토션박스 위치, 토션박스 폭과 같은 블레이드 단면 설계변수들이 결정되었다.

• Steel and Composite Structures
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• 제18권3호
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• pp.603-621
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• 2015

In this study, theoretical models and design procedures of the behavior of thin-walled simply supported steel beams with an open cross section under a large torsional effect are presented. I-sections were chosen as the cross section types. Firstly, the widely used differential equations for the lateral buckling for the pure bending moment effect in a beam element were adopted for the various moment distributions along the span of the beam. This solution was obtained for both mono-symmetric and bisymmetric sections. The buckling loads were then obtained by using the energy method. When using the energy method to solve the problem, it is possible to locate the load not only on the shear center but also at several points of the section depth. Buckling loads were obtained for six different load types. Results obtained for different load and cross section types were checked with ABAQUS software and compared with several standard rules.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.401-413
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• 2022

This paper provides a simple method by which to estimate the cross-section stress profiles for nozzles designed according to ASME Code Section III. Further, this method validates the effectiveness of earlier work performed by the authors on standard nozzles. The method requires only the geometric information of the pressure vessel and the attached nozzle. A PWR direct vessel injection nozzle, a PWR outlet nozzle, a PWR inlet nozzle and a BWR recirculation outlet nozzle are selected based on their corresponding specific designs, e.g., a varying nozzle radius, a varying nozzle thickness and an outlet nozzle boss. A cross-section stress profile comparison shows that the estimates are in good agreement with the finite element analysis results. Differences in stress intensity factors calculated in accordance with ASME BPVC Section XI Appendix G are discussed. In addition, a change in the dimensions of an alternate nozzle design relative to the standard values is discussed, focusing on the stress concentration factors of the nozzle inside corner.

• Steel and Composite Structures
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• 제13권3호
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• pp.225-238
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• 2012

Steel structural elements with web-tapered I cross section, are usually made of welded thin plates. Due to the nonrectangular shape of the element, thin web section may be obtained at the maximum cross section height. The buckling strength is directly influenced by lateral restraining, end support and initial imperfections. If no lateral restraints, or when they are not effective enough, the global behaviour of the members is characterized by the lateral torsional mode and interaction with sectional buckling modes may occur. Actual design codes do not provide a practical design approach for this kind of elements. The paper summarizes an experimental study performed by the authors on a relevant number of elements of this type. The purpose of the work was to evaluate the actual behaviour of the web tapered beam-columns when applying different types of lateral restraints and different web thickness.

• 한국생산제조학회지
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• 제21권3호
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• pp.421-424
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• 2012

Carbon Fiber reinforced composite material can be designed for the optimized performances of structural member that have achieve appropriate mechanical properties with cross-sectional shape, fiber direction, stacking sequence and thickness. So there are needed extensive databases each optimal design of CFRP structural member by impact through the preparation of different shape, interface number, thickness and stacking angle. When pressure is applied to structural member, compression, bending and torsion is shown on the corresponding member. For the effective utilization of fiber reinforced composite material as main structural member, optimized design technology should be established to maximize mechanical properties for compression, bending and torsion. In this paper, CFRP prepreg sheet with different stacking angle is manufactured in CFRP and hybrid(Al+CFRP) with circular cross-section. Strength and stiffness is gotten respectively by flexure test. CFRP structure and hybrid structure can be compared with each other. The best design guideline can be analyzed by use of this study result.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.183-189
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• 2016

In this paper, an optimization study on a helicopter rotor blade cross-section was made. Generalization was made to the baseline cross-section to simplify the analysis. To have better performance in aeroelastic response, with the aerodynamic center being the origin of the baseline, the distance between aerodynamic center and shear center, and the distance between mass center and shear center of the blade were minimized. For efficient searching of optimum solutions over the design space, grid search method, which is a method of graphical search was used. Two design variables, radius of balancing weight at leading edge, and offset of the spar from leading edge were selected for the study. Cubic spline interpolation method was used to accommodate searching of the optimum solution. 2-Leveled searching system was devised in accordance with the interpolation method. Optimum solution was found to show 6% decrease in both distance between aerodynamic center and shear center, and mass center and shear center to the baseline.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.337-340
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• 2008

The cross section shape of intermediate die is one of important parameters to obtain dimensional accuracy of final product in shaped drawing process. Until now it has been designed by the experience or trial and error of the expert. In this study, the cross section shape of intermediate die fur spline shape is determined by the electronic field analysis, shape factor method. The result of the electronic field analysis, shape factor method has been compared with that of the present method. The effects of cross section shape on the dimensional accuracy were investigated by using FE analysis. And then the multi-stage shaped drawing experiments were performed to verify the results of FE analysis. As a result, the cross section shape from the electronic field analysis had the good dimensional accuracy. The electronic field analysis can be used for the method to obtain the cross section shape of intermediate die in shaped drawing process.

• 대한조선학회논문집
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• 제45권6호
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• pp.695-702
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• 2008

In this paper, a new numerical method is proposed to analyze near-field sonar cross section of acoustically large-sized underwater targets such as submarines. A near-field problem is converted to a far-field problem using a spherical projection method with respect to the objective target. Then, sonar cross section is calculated with a physical optics well established in far-field acoustic wave scattering problems. The analysis results of a square flat plate compared with those obtained by other method show the accuracy of the proposed method. Moreover, it is noted that the sonar cross section is varied with respect to the targeting point as well as the range. Finally, numerical analysis results of real-like underwater target such as a submarine pressure hull are discussed.