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피로수명예측을 위한 반응표면근사화와 순위선호정보를 가진 다기준최적설계에의 응용
백석흠(Seok-Heum Baek),조석수(Seok-Swoo Cho),주원식(Won-Sik Joo) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.2
In this paper, a versatile multi-criteria optimization concept for fatigue life prediction is introduced. Multi-criteria decision making in engineering design refers to obtaining a preferred optimal solution in the context of conflicting design objectives. Compromise decision support problems are used to model engineering decisions involving multiple trade-offs. These methods typically rely on a summation of weighted attributes to accomplish trade-offs among competing objectives. This paper gives an interpretation of the decision parameters as governing both the relative importance of the attributes and the degree of compensation between them. The approach utilizes a response surface model, the compromise decision support problem, which is a multi-objective formulation based on goal programming. Examples illustrate the concepts and demonstrate their applicability.
백석흠(Seok Heum Baek),윤정환(Jeong Hwan Yoon),정우성(Woo Sung Jung),하형수(Hyeong Soo Ha),정성식(Sung Sik Chung),염정국(Jeong Kuk Yeom) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.2
본 연구에서는 바이오디젤연료 혼합비변화에 대한 디젤엔진의 배기특성에 대해 조사하였다. 실험에 사용된 연료는 경유와 바이오디젤(폐식용유) 혼합연료 BD3, BD5, BD20, BD50 및 BD100을 사용하였으며, 실험변수로서 분사압력(ΔPinj)을 400bar, 600bar, 800bar, 1000bar 및 1200bar로 설정하였다. 분사압력과 바이오디젤 혼합연료 혼합비에 따른 정량적인 NOx와 Soot의 배기특성 해석을 위하여 통계학에 기초한 피어슨 상관계수와 스피어만 상관계수의 개념을 도입하였다. 본 연구의 결과로서 실험 조건 전체에 대한 피어슨 상관계수는 -0.732, 스피어만 상관계수는 -0.724로 NOx와 Soot 발생의 상관관계가 선형적이다. 특히 분사압력 800bar 조건에서 피어슨 상관계수가 -0.089으로 NOx와 Soot 배출량 상관관계가 0에 가깝기 때문에, 바이오디젤 연료 혼합비 제어를 통한 NOx와 Soot의 동시저감이 가능하다고 판단된다. In this study, the characteristics of exhaust gas as a function of the biodiesel mixing ratio were investigated. Diesel and waste oil were used for preparing mixed fuel, and the ratios of the mixed fuel were varied in the BD3~BD100 range. The injection pressures(ΔPinj) was considered as an experimental variable and was set to 400 bar, 600 bar, 800 bar, 1000 bar, and 1200 bar. Furthermore, for quantitatively analyzing the characteristics of exhaust gas(NOx and Soot), the concepts of Pearson correlation coefficient and Spearman rank-order correlation coefficient based on statistics were introduced. Consequently, it was found that the correlation of the emission of NOx and Soot is linear, and the Pearson and Spearman coefficients are -0.732 and -0.724, respectively, under all analysis conditions. Especially, for the injection pressure of 800 bar, a simultaneous reduction in NOx and Soot emission is possible by controlling the biodiesel mixing ratio. This is because the correlation coefficients of NOx and Soot emissions were nearly 0, as the Pearson correlation coefficient was -0.089.
백석흠(Seok-Heum Baek),김강민(Kang-Min Kim),조석수(Seok-Swoo Cho),이경영(Kyoung-Young Lee),홍순혁(Soon-Hyeok Hong),장득열(Deuk-Yul Jang),주원식(Won-Sik Joo) 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-
Compromise decision support problems are used to model engineering decisions involving multiple trade-offs. These methods typically rely on a summation of weighted attributes to accomplish trade-offs among competing objectives. This paper gives an interpretation of the decision parameters as governing both the relative importance of the attributes and the degree of compensation between them. The approach utilizes a mathematical decision model, the compromise decision support problem, which is a multi-objective formulation based on mathematical programming and goal programming. Examples are included to illustrate the effect of fatigue reliability design on the optimization process.
메타모델 기반 다단계 해석을 이용한 순차적 최적설계 알고리듬
백석흠(Seok-Heum Baek),김강민(Kang-Min Kim),조석수(Seok-Swoo Cho),장득열(Deuk-Yul Jang),주원식(Won-Sik Joo) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.9
An efficient sequential optimization approach for metamodel was presented by Choi et al.(13) This paper describes a new approach of the multilevel optimization method studied in Refs. [2] and [20,21]. The basic idea is concerned with multilevel iterative methods which combine a descent scheme with a hierarchy of auxiliary problems in lower dimensional subspaces. After fitting a metamodel based on an initial space filling design, this model is sequentially refined by the expected improvement criterion. The advantages of the method are that it does not require optimum sensitivities, nonlinear equality constraints are not needed, and the method is relatively easy to understand and use. As a check on effectiveness, the proposed method is applied to an engineering example.
세라믹 하니컴 담체의 3차원 유한요소해석을 위한 등가탄성방법의 효과적인 접근
백석흠(Seok Heum Baek),조석수(Seok Swoo Cho) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.3
세라믹 모노리스 촉매는 두 계층으로 구성된 하니컴 구조이다. 하니컴 구조는 열유동 및 구조해석에서 연속체로 고려한다. 하니컴 구조의 등가 기계적 물성은 유한요소해석(FEA) 시험편으로부터 얻어진다. 강도 시험과 FEA는 ASTM C1674-08에서 소개된 사각 단위 셀 시험편과 시험방법에 의해 각각 달성되었다. 코제라이트 세라믹 층과 워시코트 층 사이의 접합계수는 거의 0이다. FEA 시험편은 접합계수에 기반한 모델로 만들어진다. 세라믹 모노리스 담체에서 탄성계수, 푸아송 비와 열적 물성은 FEA 시험편에 의해 결정하였다. A ceramic monolithic catalyst is a honeycomb structure that consists of two layers. The honeycomb structure is regarded as a continuum in structure and heat-flow analysis. The equivalent mechanical properties of the honeycomb structure were determined by performing finite element analysis (FEA) for a test specimen. Bending strength experiments and FEA of the test specimen used in ASTM C1674-08 standard test were performed individually. The bonding coefficient between the cordierite ceramic layer and the washcoat layer was almost zero. The FEA test specimen was modeled on the basis of the bonding coefficient. The elastic modulus, Poisson’s ratio, and the thermal properties of the ceramic monolithic substrate were determined by performing the FEA of the test specimen.
유체 구조 상호작용 문제를 가진 다공성 촉매 담체에서 실동경계조건의 역문제 해석을 위한 최적화 기법
백석흠(Seok Heum Baek),조석수(Seok Swoo Cho),김현수(Hyun Su Kim) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.10
이 논문은 촉매 담체에서 열유동 및 구조해석의 실동경계조건에 대한 역문제 해법을 나타낸다. 촉매 담체의 배기가스 정화효율은 열유동 매개변수와 촉매 성분 등에 영향을 받고 열유동 균일도에 의해 평가된다. 역문제의 정식화-열유동 매개변수(입구 온도, 속도, 반응열, 대류열전달계수)를 얻고-와 직접 문제-주어진 출구 온도 분포로부터 평가-를 설명하였다. 실험계획법과 반응표면 최적화 기법은 제안된 역문제 해결을 위해 이용하였다. 촉매 담체의 온도 분포는 예측된 열유동 매개변수에 대한 열유동 해석에 의해 얻었다. 열응력과 내구성 평가는 이 온도 분포에 기반해서 수행하였다. 역문제 접근 방법의 유효성과 정확성은 반응표면모델과 측정된 실차 시험과 좋은 일치를 달성함으로써 설명하였다. This paper presents a solution to the inverse problem for the service boundary conditions of thermal-flow and structure analysis in a catalyst substrate. The exhaust-gas purification efficiency of a catalyst substrate is influenced by the shape parameter, catalyst ingredients and so on and is estimated by the thermal flow uniformity. The formulations of the inverse problem of obtaining the thermal-flow parameters (inlet temperature, velocity, heat of reaction, convective heat-transfer coefficient) and the direct problem of estimating from a given outlet temperature distribution are described. An experiment was designed and the response-surface optimization technique was used to solve the proposed inverse problem. The temperature distribution of the catalyst substrate was obtained by thermal-flow analysis for the predicted thermal-flow parameters. The thermal stress and durability assessments for the catalyst substrate were performed on the basis of this temperature distribution. The efficiency and accuracy of the inverse approach have been demonstrated through the achievement of good agreement between the thermal-flow response surface model and the results of experimental vehicle tests.
커먼레일 디젤엔진에서 바이오디젤 연료의 혼합비율에 대한 배기가스의 특성 평가
백석흠(Seok Heum Baek),윤정환(Jeong Hwan Yoon),정우성(Woo Sung Jung),하형수(Hyeong Soo Ha),정성식(Sung Sik Chung),염정국(Jeong Kuk Yeom) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.5
In this study, the characteristics of exhaust gas according to mixing ratio of bio diesel fuel were evaluated. The fuels which was used in this study are biodiesel mixed fuel of 3%, 5%, 20%, 50% and 100% Also, injection pressures as a experimental variable were set to 400bar, 600bar, 800bar, 1000bar and 1200bar. Generally, unlike Soot emissions, the more injection pressure is applied, the more nitrogen oxides(NOx) are occurred. To analyze experiment data about NOx and Soot, Pearson correlation coefficient and Spearman rank-order correlation coefficient were used. Consequently, the values of Pearson correlation and Spearman rank-order correlation coefficient were ?0.732 and ?0.724. There is little difference between the two values. Since the two values is less than l, the relation of NOx and Soot in linear. At 800bar, Pearson correlation coefficient is ?0.89. Therefore, in order to remove NOx and Soot, this paper reveal that 800bar condition is advantageous.