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이석제,김인걸,Lee, Seok-Je,Kim, In-Gul 한국군사과학기술학회 2012 한국군사과학기술학회지 Vol.15 No.1
In this paper, the deterministic optimal design for the tail plane made of composite materials is conducted under the deterministic loading condition and compared with that of the metallic materials. Next, the reliability analysis with five random variables such as loading and material properties of unidirectional prepreg is conducted to examine the probability of failure for the deterministic optimal design results. The MATLAB programing is used for reliability analysis combined with FEA S/W(COMSOL) for structural analysis. The laminated composite is assumed to the equivalent orthotropic material using classical laminated plate theory. The response surface methodology and importance sampling technique are adopted to reduce computational cost with satisfying the accuracy in reliability analysis. As a result, structural weight of composite materials is lighter than that of metals in deterministic optimal design. However, the probability of failure for the deterministic optimal design of the tail plane structures is too high to be neglected. The sensitivity of each variable is also estimated using probabilistic sensitivity analysis to figure out which variables are sensitive to failure. The computational cost is considerably reduced when response surface methodology and importance sampling technique are used. The study of the computationally inexpensive method for reliability-based design optimization will be necessary in further work.
반응면 기법을 이용한 복합재 평판의 신뢰도 및 민감도해석
이석제(Seokje Lee),장문호(Moon-Ho Jang),김재기(Jae-Ki Kim),문정원(Jung-Won Moon),김인걸(In-Gul Kim) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.4
섬유강화 복합재료는 무게 절감을 위해 다양한 공학 분야에 널리 사용되고 있다. 각 층의 재료 물성치는 일반적인 금속재료에 비해 더 불확실한 것으로 알려져 있으며 하중 방향에 따라 매우 민감하게 반응한다. 그러므로, 복합재 적층판의 설계에서 불확실성을 고려하는 것은 매우 중요하다. 본 논문에서는 COMSOL과 MATLAB을 이용하여 끝단 변위가 설계 요구조건으로 정의된 경우, 재료 물성치를 확률변수로 하는 복합재 적층판에 대한 신뢰성 해석을 수행하였다. 또한 근사기법의 효율성과 정확성을 확인하고 확률론적 민감도 해석을 수행하였다. 결과적으로 수중 비행체의 비행자세 안정장치에 대한 개선된 설계 방법의 적용가능성을 제시할 수 있었다. Advanced fiber-reinforced laminated composites are widely used in various fields of engineering to reduce weight. The material property of each ply is well known; specifically, it is known that ply is less reliable than metallic materials and very sensitive to the loading direction. Therefore, it is important to consider this uncertainty in the design of laminated composites. In this study, reliability analysis is conducted using COMSOL and MATLAB interactions for a laminated composite plate for the case in which the tip deflection is the design requirement and the material property is a random variable. Furthermore, the efficiency and accuracy of the approximation method is identified, and a probabilistic sensitivity analysis is conducted. As a result, we can prove the applicability of the advanced design method for the stabilizer of an underwater vehicle.
복합재 샌드위치 구조의 개선된 확률론적 설계 및 신뢰성 기반 최적설계
이석제 ( Seok Je Lee ),김인걸 ( In Gul Kim ),조우제 ( Woo Je Cho ),설창원 ( Chang Won Shul ) 한국복합재료학회 2013 Composites research Vol.26 No.1
복합재료 샌드위치 구조는 굽힘 강성을 향상시키고 복합재 적층판에 비해 30% 이상의 무게를 절감할 수 있다. 그러나 일반 금속에 비해 제작과정에서 발생되는 재료물성의 불확실성이 많이 내재되어 있으므로 신뢰성 기반 확률론적 설계방법이 요구된다. 본 논문에서는 안전계수를 이용한 고전적인 설계 방법이 구조물의 안전을 보장하지 않는다는 확률론적 증거를 제시하기 위하여 단순화된 복합재 샌드위치 동체에 대해 PMS(Probabilistic Margin of Safety)를 계산하였다. 이 과정에서 CMCS(Crude Monte-Carlo Simulation)에 의해 계산된 확률밀도함수를 이용하였다. 더 나아가 신뢰성 기반 최적설계를 수행하고 효율적인 계산을 위해 RBDO-MPDF(RBDO by Moving PDF) 방법을 제시하였다. 본 논문의 결과는 구조물의 신뢰성을 보장하기 위한 개선된 설계 방법과 효율적인 신뢰성 기반 최적설계 방법 연구에 유용할 것이다. Composite sandwich structure can improve the specific bending stiffness significantly and save the weight nearly 30 percent compared with the composite laminates. However, it has more inherent uncertainties of the material property caused by manufacturing process than metals. Therefore, the reliability-based probabilistic design approach is required. In this paper, the PMS(Probabilistic Margin of Safety) is calculated for the simplified fuselage structure made of composite sandwich to provide the probabilistic reasonable evidence that the classical design method based on the safety factor cannot ensure the structural safety. In this phase, the probability density function estimated by CMCS(Crude Monte-Carlo Simulation) is used. Furthermore, the RBDO(Reliability-Based Design Optimization) under the probabilistic constraint are performed, and the RBDO-MPDF(RBDO by Moving Probability Density Function) is proposed for an efficient computation. The examined results in this paper can be helpful for advanced design techniques to ensure the reliability of structures under the uncertainty and computationally inexpensive RBDO methods.
서울시 정비사업의 주택공급 특성 및 공급가능 물량 분석
이삼수(Lee, Sam-Su),이석제(Lee, Seo-kje),권치흥(Kwon, Chi-hung) 한국부동산정책학회 2020 不動産政策硏究 Vol.21 No.2
This paper analyzed the contribution of housing supply based on the progress of redevelopment and reconstruction projects among the improvement project in Seoul. By analyzing the project promotion stage of the improvement project, the amount of housing available from 2020 to 2035 was calculated. The implications of the improvement project for the housing supply policy are as follows. First, housing supply characteristics accounted for over 70% of apartments compared to the total number of homes supplied in the 2000s, but fell below 50% after 2010. Second, from 2005 to 2018, the contribution of the housing supply to the improvement project compared to the new number of housing supply has been continuously decreasing to about 22.2%. Third, it is expected that total of 390,000 units will be supplied by 2035 by the improvement project. And it is expected to supply 85,000 units by 25, 16,200 units by 26-30, and 14,200 units by 30. Lastly, the amount of housing available for each period of completion of the improvement project is expected to surge to 15,000 units annually from 20 to 25 years and 32,000 units from 26 to 30 years. Therefore, the improvement project takes a long period of time, and there is a limit to the short-term housing supply policy. It is necessary to convert the old housing in the down town into a housing policy for rational housing stock management.