응력 제한조건하의 신뢰성 기반 형상 최적설계

오영규(Young-kyu Oh),박재용(Jae-kyu Oh),임민규(Min-gyu Im),박재용(Jae-yong Park),한석영(Seog-young Han) 한국생산제조학회 2010 한국생산제조학회지 Vol.19 No.4

The objective of this study is to integrate reliability analysis into shape optimization problem using the evolutionary structural optimization (ESO) in the application example. Reliability-based shape optimization is formulated as volume minimization problem with probabilistic stress constraint under minimization max. von Mises stress and allow stress. Young's modulus, external load and thickness are considered as uncertain variables. In order to compute reliability index, four methods, i.e., reliability index approach (RIA), performance measure approach (PMA), single-loop single￢vector (SLSV) and adaptive-loop (ADL), are used. Reliability-based shape optimization design process is conducted to obtain optimal shape satisfying max. von Mises stress and reliability index constraints with the above four methods, and then each result is compared with respect to numerical stability and computing time.

밀도분포법을 이용한 부재의 연결구조 최적화

한석영,유재원 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.4

Most engineering products contain more than one component. Failure occurs either at the connection itself or in the component at the point of attachment of the connection in many engineering structures. The allocation and design of connections such as bolts, spot-welds, adhesive etc. usually play an important role in the structure of multi-components. Topology optimization of connection component provides more practical solutions in design of multi-component connection system. In this study, a topology optimization based on density distribution approach has been applied to optimal location of fasteners such as T-shape, L-shape and multi-component system. From the results, it was verified that the number of iteration was reduced, and the optimal topology was obtained very similarly comparing with ESO method. Therefore, it can be concluded that the density distribution method is very suitable for topology optimization of multi-component structures.

좌굴 하중을 고려한 프레임 구조물의 최적 설계

한석영,진경욱 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.2

In this paper, the comparison of the first order approximation schemes such as SLP (sequential linear programming), CONLIN (convex linearization), MMA(method of moving asymptotes) and the second order approximation scheme, SQP(sequential quadratic programming) was accomplished for optimization of nonlinear structures. It was found that MMA and SQP are the most efficient methods for optimization. But the number of function call of SQP is much more than that of MMA. Therefore, when it is considered with the expense of computation, MMA is more efficient than SQP. In order to examine the efficiency of MMA for complex optimization problem, it was applied to the helicopter tail boom con-sidering column buckling and local wall buckling constraints. It is concluded that MMA can be a very efficient approxima-tion scheme from simple problems to complex problems.

마이크로 유전자 알고리즘을 이용한 구조 최적설계

한석영,최성만 한국공작기계학회 2003 한국공작기계학회 춘계학술대회논문집 Vol.2003 No.-

SGA (Single Genetic Algorithm) is a heuristic global optimization method based on the natural characteristics and uses many populations and stochastic rules. Therefore SGA needs many function evaluations and takes much time for convergence. In order to solve the demerits of SGA, μGA(Micro-Genetic Algorithm) has recently been developed. In this study, μGA which have small populations and fast convergence rate, was applied to structural optimization with discrete or integer variables such as 3, 10 and 25 bar trusses. The optimized results of μGA were compared with those of SGA. Solutions of μGA for structural optimization were very similar or superior to those of SGA, and faster convergence rate was obtained. From the results of examples, it is found that μGA is a suitable and very efficient optimization algorithm for structural design.

대한상하수도학회·한국수자원공사 공동주최 2003년도 제2회 부상분리 국제워크샵 보고문

한무영,김진호,독고석,곽동희,류석위 대한상하수도학회 2003 상하수도학회지 Vol.17 No.6

밀도분포법을 이용한 부재의 연결구조 최적화

한석영,유재원,박재용 한국공작기계학회 2003 한국공작기계학회 춘계학술대회논문집 Vol.2003 No.-

Most engineering products contain more than one component. Failure occurs either at the connection itself or in the component at the point of attachment of the connection in many engineering structures. The allocation and design of connections such as bolts, spot-welds, adhesive etc. usually play an important role in the structure of multi-components. Topology optimization of connection component provides more practical solution in design of multi-component connection system. In this study, a topology optimization based on density distribution approach has been applied to optimal location of fasteners such as T-shape, L-shape and multi-component connection system. From the results, it was verified that the number of iteration was reduced, and the optimal topology was obtained very similarly comparing with ESO method. Therefore, it can be concluded that the density distribution method is very suitable for topology optimization of multi-component structures.

마이크로 믹서의 형상 최적화

한석영,김성훈 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-

In this study, shape optimization of micro-static mixer with a cantilever beam was accomplished for maximizing the mixing efficiency by using successive response surface approximations. Variables were chosen as the length of cantilever beam and the angle between horizontal and the cantilever beam. Sequential approximate optimization method was used to deal with both highly nonlinear and non-smooth characteristics of flow field in a micro-static mixer. Shape optimization problem of a micro-static mixer can be divided into a series of simple subproblems. Approximation to solve the subproblems was performed by response surface approximation, which does not require the sensitivity analysis. To verify the reliability of approximated objective function and the accuracy of it, ANOVA analysis and variables selection method were implemented, respectively. It was verified that successive response surface approximation worked very well and the mixing efficiency was improved very much comparing with the initial shape of a micro-static mixer.

진화적 구조 최적화를 위한 요소 제거법 비교 연구

한석영,이동진 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.5

In case of ESO(evolutionary structural optimization) which is one of topology optimization methods, the element removal ratio is fixed throughout topology optimization by 1 or 2%. As a result it has no flexibility for various types of, structures and thus the rate of convergence might not be efficient. Thus various element removal methods were developed in order to improve the efficiency of ESO. In this paper, various element removal methods for ESO are compared with each other for a bracket and a short cantilever. In addition, a new improved bi-directional element removal method is sug-gested in order to obtain much better optimized topology. From the comparative results of the examples, it is verified that all of the developed various element removal methods arc very effective, and the suggested element removal method is the most effective.

免疫血淸學的 方法에 依한 姙産婦의 Toxoplasma 抗體價分布에 關한 調査硏究

韓炳錫,李英河,羅榮彦,辛大煥 충남대학교 의과대학 지역사회의학연구소 1990 충남의대잡지 Vol.17 No.1

In order to evaluate the Toxoplasma antibody titers, authors were examined sera of 117 pregnant women by enzyme-linked immunosorbent assay(ELISA), methlyene blue dye test and indirect latex agglutination test. The results were obtained as follows: 1. The ELISA values to the Toxoplasma antibody showed less than 0.200 in 2 cases(1.7%), 0.20 0-0.299 in 13 cases(11.1%), 0,300-0.399 in 29 cases(24.8%), 0.400-0.499 in 143 cases(12.0%), 0.500-0.599 in 26 cases(22.2%), 0.600-0.699 in 19 cases(16.2%), 0.700-0.799 in 6 cases(5.1%), 0.800-0.899 in 7 cases(6.0%), more than 0.900 in 1 case(0.9%), respectively. Regard to positive ELISA values were more the 0.800, positive rates of ELISA were 6.9%. 2. The dye test antibody titers showed less than 1:4 in 70 cases (59.8%), 1:4 in 27 cases(23.1%), 1:16 in 13 cases(11.1%), 1:64 in 6 cases(5.1%), and 1:256 in 1case(0.9%), respectively. Regard to 1:64 or more tilers of diluted sere were positive, the positive rates of dye test were 6.0%. 3. The Toxoplasma antibody titers by indirect latex agglutination test were less than 1:2 in 9 cases(7.7%), 1:2 in 47 cases(40.2%), 1:4 in 27 cases(23.1%), 1:8 in 21 cases(17.9%), 1:16 in 7 cases(6.0%), 1:32 in 5 cases(4.3%), and 1:64 in 1 cases(0.9%), respectively. Regard to 1:32 or more titers of diluted sera positive, the positive rates of indirect latex agglutination test were 5.2% 4. There were correlation between dye test antibody titers and ELISA values(correlation coefficient, r=0.414). The present study revealed that Toxoplasma antibody titers of pregnant women by various immunoserologic methods showed 5.1∼6.9%.

열림 모드에 대한 형상 최적화

한석영,송시엽 한국공작기계학회 2001 한국공작기계학회 춘계학술대회논문집 Vol.2001 No.-

The relationship between structural geometry and number of life cycles to failure is investigated to improve the fatigue life of structural components. The linear elastic fracture mechanics(LEFM) approach is integrated with shape optimal design methodology. The primary objective of this study is to decide an optimal shape for enhancing the life of the structure. The results from LEFM analyses are used in the fatigue model to predict the life of the structure before failure is occurred. The shape of the structure is optimized by using the growth strain method. Relevant issues such as problem formulation, finite element modeling are explained. Three design examples are solved, and the results show that, with proper shape changes, the life of structural systems subjected to fatigue loads can be enhanced significantly.