• 한국항공우주학회지
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• 제38권7호
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• pp.716-726
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• 2010

본 연구에서는 공기역학과 비선형 구조해석을 통합한 다분야 최적설계 최적화(MDO)프레임웍을 사용하여 항공기 날개의 설계를 수행하였다. MDO 문제 중 해결해야할 가장 큰 문제인 자동화를 해결하여 전 과정이 자동화되게 하였다. 공력해석은 FLUENT를 사용하였으며 이를 위한 격자는 CATIA의 파라미터 모델과 Gambit을 사용하여 자동으로 생성되도록 하였다. 전산구조해석을 위한 격자는 CATIA의 파라미터 모델과 NASTRAN- FX의 비주얼 베이직 스크립트를 사용하여 자동으로 생성되도록 하였다. 구조해석은 비선형성을 고려하여 ABAQUS를 사용하였다. 최적화 방법은 전역해를 구하기 유리한 반응표면법을 사용하였다. 목적함수는 날개 무게의 최소화이고 제약 조건은 양항비, 날개의 변위 그리고 구조응력량으로 정하였다. 그리고 설계변수는 가로세로비, 테이퍼비, 후퇴각 그리고 상하스킨의 두께로 정의하였다. 최적화 설계결과는 본 자동화 MDO프레임웍이 성공적으로 구성되었음을 보여주었다.

• 한국방재학회 논문집
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• 제10권3호
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• pp.31-38
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• 2010

본 연구에서는 교량 구조물-궤도 종방향 상호작용, 교량 구조물-차량 상호작용을 고려한 신뢰성 최적설계 방법을 제안하고, 알고리즘의 개발을 통하여 본 연구에서 제안한 방법의 효율성을 검증하였다. 구조해석 프로그램은 ABAQUS를 사용하였으며, 최적화 방법은 Automated Design Synthesis(ADS)에서 신뢰성면에서 우수한 ALM-BFGS방법을 사용하였다. 일반적으로 ALM-BFGS방법은 최적해 방향을 탐색하는데 있어 1방향 탐색을 하지 않으며 Push-Off Factor 값이 보통 0.1~0.2에서 대부분 수렴하나 본 연구에서는 'Heuristic Decision Method' 의하여 결정된 Push-Off Factor 값이 90일 때 1방향 탐색인 Golden Section Method의 적용이 필요하였으며, 알고리즘이 잘 수렴함을 확인하였다. 구조물-궤도 종방향 상호작용, 구조물-차량의 상호작용에 의한 응답을 제약조건으로 설정하여 단면 설계시 반영될 수 있도록 하였다. 본 연구는 구조물-궤도 종방향 상호작용 및 구조물-차량 상호작용을 고려한 설계기법에 대한 효율성 및 경제성을 증명하기 위하여 5${\times}$(1@50m) 2주형 강합성 거더교에 대한 최적설계를 수행하였으며, 본 연구에서 제안하는 상호작용을 고려하는 설계기법이 기존의 상호작용을 고려하지 않은 설계방법보다 경제적이며 효율적임을 확인하였다.

• International Journal of Precision Engineering and Manufacturing
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• 제2권4호
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• pp.5-11
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• 2001

Vibration and noise of gears is doc to the transmission error and the vibration exciting force caused by the periodically alternating tooth stiffness. Transmission error is the rotation delay between driving and driven gear caused by manufacturing error, alignment error in assembly and so on. Tooth stiffness changes with the proceeding mesh of teeth. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification. end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the meshing analysis of gears. Formulated constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth bending strength, surface durability, and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. We also investigate the relation between the aspect ratio and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is expected to be practically useful to resolve the problem of vibration of helical gears.

• 한국유체기계학회 논문집
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• 제5권3호
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• pp.40-45
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• 2002

Since the previous cut-and-try design algorithm requires much cost and time, the automated design technique with the CFD and optimum design algorithm has recently been concerned. In this work, the Navier-Stokes equation was solved to gain more detailed viscous flow information of cascade with rotor-stator interactions. The H-grid embedded by O-grid was generated to obtain more accurate solution by eliminating the branch cut of H-grid near airfoil surface. To handle the relative motion of the rotor to the stationary stator, the sliding multiblock method was applied and the cubic-spline interpolation was used on the block interface boundary. To validate present procedure, the time-averaged aerodynamic loads were compared with experimeatal data. A good agreement was obtained. The Modified Method of Feasible Direction (MMFD) was used to carry out the sensitivity analysis of the change of aerodynamic performance by the changes of the cascade geometry. The present optimization of the cascade gave a dramatic reduction of the drag while the lift maintains at the value within the user-specified tolerance.

• Computers and Concrete
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• 제26권1호
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• pp.1-10
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• 2020

In this paper, a procedure for automated optimized design of reinforced concrete frames has been presented. The procedure consists of formulation and solution of the design problem in the form of an optimization problem. The minimization of total cost of R/C frame has been taken as the objective of optimization problem. In this research, consistent approximation method is applied to explicitly formulate constraints and objective function in terms of the design variables. In the presented method, the primary optimization problem is replaced with a sequence of explicit sub-problems. Each sub-problem is efficiently solved using the Sequential Quadratic Programming (SQP) method. The proposed method is demonstrated through a four-story frame and an eight-story frame, and the optimum results are compared with those in the available literature. It is shown that the proposed method can be easily applied to obtain rational, reliable, economical and practical designs for Reinforced Concrete Moment Resisting Frames (RCMRFs) while it is converged after a few analyses.

• 산업경영시스템학회지
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• 제30권2호
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• pp.99-105
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• 2007

According to the automated manufacturing processes followed by the development of computer manufacturing technologies, products or quality characteristics produced on the processes have measured and recorded automatically. Much amount of data daily produced on the processes may not be efficiently analyzed by current statistical methodologies (i.e., statistical quality control and statistical process control methodologies) because of the dimensionality associated with many input and response variables. Although a number of statistical methods to handle this situation, there is room for improvement. In order to overcome this limitation, we integrated data mining and robust design approach in this research. We find efficiently the significant input variables that connected with the interesting response variables by using the data mining technique. And we find the optimum operating condition of process by using RSM and robust design approach.

• 대한기계학회논문집A
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• 제26권4호
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• pp.720-730
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• 2002

Automated design of large structures requires efficient and accurate optimization algorithms because of a large number of design variables and design constraints. The objective of this study is to examine the characteristics of the Kreisselmeier -Steinhauser envelope function and to investigate va tidily of accumulating constraint functions into a small number of constraint functions or even into a single constraint function. The commercial package DOT is adopted as a local optimizer. The optimum results using the envelope function are compared with those of the conventional method for a number of numerical examples and the differences between them are shown to be negligible.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.692-697
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• 2010

In this paper, a design program for electric railway pole foundation was developed by applying the estimation study performed by Korean Railway. There are two kinds of shapes in the cross-section of electric railway pole foundation: rectangle and circle. In foundation designing, The rectangular foundation should be satisfied with vertical, horizontal and moment equilibrium equations. On the other hand, the circular foundation should be satisfied with horizontal and moment equilibrium equations. The design program was coded into MFC(Microsoft Foundation Class) by MS Visual C. The equation's roots in the program were obtained by Incremental Search method. Dialog and property sheet(Wizard Mode) input windows were selected for user-friendliness. The biggest advantage of this program is to find an optimum depth in a given section.

• 한국정밀공학회지
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• 제17권11호
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• pp.199-205
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• 2000

The vibration and noise of gears is due to the vibration exciting force caused by the tooth stiffness which changes periodically as the mesh of teeth proceeds and by the transmission error, that is, the rotation delay between driving gear and driven gear caused by manufacturing error and alignment error in assembly and so on. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification, end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the mesh analysis of gears. The constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth fillet stress, surface durability and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. And, since the aspect ratio is an important parameter of tooth modification, we investigate the relation between it and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is to be utilized to resolve the problem of vibration of helical gears.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.662-674
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• 2017

This paper describes the multidisciplinary design optimization (MDO) process of a tailless unmanned combat aerial vehicle (UCAV) using global variable fidelity aerodynamic analysis. The developed tailless UAV design framework combines multiple disciplines that are based on low-fidelity and empirical analysis methods. An automated high-fidelity aerodynamic analysis is efficiently integrated into the MDO framework. Global variable fidelity modeling algorithm manages the use of the high-fidelity analysis to enhance the overall accuracy of the MDO by providing the initial sampling of the design space with iterative refinement of the approximation model in the neighborhood of the optimum solution. A design formulation was established considering a specific aerodynamic, stability and control design features of a tailless aircraft configuration with a UCAV specific mission profile. Design optimization problems with low-fidelity and variable fidelity analyses were successfully solved. The objective function improvement is 14.5% and 15.9% with low and variable fidelity optimization respectively. Results also indicate that low-fidelity analysis overestimates the value of lift-to-drag ratio by 3-5%, while the variable fidelity results are equal to the high-fidelity analysis results by algorithm definition.