• 한국정밀공학회지
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• 제22권3호
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• pp.146-153
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• 2005

In this paper, a multi-step optimization using genetic algorithm with variable penalty function is introduced to the structural design optimization of a grinding machine. The design problem, in this study, is to find out the optimum configuration and dimensions of structural members which minimize the static compliance, the dynamic compliance, and the weight of the machine structure simultaneously under several design constraints such as dimensional constraints, maximum deflection limit, safety criterion, and maximum vibration amplitude limit. The first step is shape optimization, in which the best structural configuration is found by getting rid of structural members that have no contributions to the design objectives from the given initial design configuration. The second and third steps are sizing optimization. The second design step gives a set of good design solutions having higher fitness for lightweight and minimum static compliance. Finally the best solution, which has minimum dynamic compliance and weight, is extracted from the good solution set. The proposed design optimization method was successfully applied to the structural design optimization of a grinding machine. After optimization, both static and dynamic compliances are reduced more than 58.4% compared with the initial design, which was designed empirically by experienced engineers. Moreover the weight of the optimized structure are also slightly reduced than before.

• 한국항공우주학회지
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• 제30권6호
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• pp.107-115
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• 2002

본 연구에서는 다중스파 항공기 날개 구조물의 유한요소 이상화 방법이 날개의 내력분포, 치수 및 중량에 어떠한 영향을 미치는지를 살펴보았다. 구조물의 유한요소 이상화 방법에 따라 총 18가지의 날개 모델을 구축하고 4가지의 외부하중 조건을 적용하였다. MSC/NASTRAN과 MSC/PATRAN을 이용하여 모든 구조물이 주어진 하중조건 모두에 대해 허용치 이내의 응력과, 가공을 위한 최소치 이상의 치수를 가지도록 하는 알고리즘을 별도로 개발하였다. 해석결과 날개의 내력분포와 예상중략에 가장 큰 영향을 미치는 것은 외피이고, 스파나 립의 이상화 방법의 효과는 상대적으로 작은 것으로 나타났다. 일반적인 예상과는 달리 굽힘강성을 가진 요소들을 사용한 모델이, 굽힘응력의 효과로 인해, 굽힘강성이 없는 요소를 사용한 모델에 비해 더 큰 예상중량을 보이는 것을 알 수 있었다. 본 연구의 결과로부터, 설계자는 가능하면 모든 구조물의 굽힘강성을 고려한 해석을 수행하거나 그렇지 못할 경우 각 구조물의 특성에 대한 신중한 사전 검토를 거칠 것을 권장한다.

• Environmental Engineering Research
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• 제20권3호
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• pp.268-276
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• 2015

Solid waste production increases due to population and consumption increments. Landfill is the ultimate destination for all kinds of municipal solid waste; and is the most convenient waste disposal method in developing countries. To minimize investment and operational costs and society's opposition towards locating landfills nearby, proper landfill sizing and siting are essential. In this study, solid waste forecasting using Autoregressive Integrating Moving Average (ARIMA) was integrated with government future plans and waste composition to estimate the required landfill area for the state of Selangor, Malaysia. Landfill siting criteria were then prioritized based on expert's preferences. To minimize ambiguity and the uncertainty of the criteria prioritizing process, the expert's preferences were treated using integrated Median Ranked Sample Set (MRSS) and Analytic Hierarchy Process (AHP) models. The results show that the required landfill area is 342 hectares and the environmental criteria are the most important; with a priority equal to 48%.

• 비파괴검사학회지
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• 제20권1호
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• pp.1-9
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• 2000

본 연구에서는 유도초음파를 이용하여 열 교환기와 증기발생기 튜브의 결함을 비파괴적으로 탐상하고 그 크기를 산정하였다. 이론적인 해석을 위해 인코넬 (Inconel) 튜브에 대한 위상 및 군속도 분산선도를 Longitudinal 모드와 Flexural 모드에 대해 구하였다. 튜브의 원주방향 레이저노치와 튜브 지지대 하단의 방전가공결함(EDM wear)을 각각 비대칭 및 대칭 탐촉자 세트를 사용하여 탐상하였다. 실험결과 방전가공결함은 L(0, 2), L(0, 3), L(0, 4) 모드로 탐상되었으며, 그 중 L(0, 4) 모드가 결함으로부터 가장 잘 반사되었다. 레이저노치의 경우에는 L(0, 1) 모드 주변의 Flexural 모드가 결함을 탐상하고 크기를 산정하는데 사용될 수 있음을 보였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.351-358
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• 2005

Many methods have been developed and are in use for structural size optimization problems, In which the cross-sectional areas or sizing variables are usually assumed to be continuous. In most practical structural engineering design problems, however, the design variables are discrete. This paper proposes an efficient optimization method for structures with discrete-sized variables based on the harmony search (HS) meta-heuristic algorithm. The recently developed HS algorithm was conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary In this paper, a discrete search strategy using the HS algorithm is presented in detail and its effectiveness and robustness, as compared to current discrete optimization methods, are demonstrated through a standard truss example. The numerical results reveal that the proposed method is a powerful search and design optimization tool for structures with discrete-sized members, and may yield better solutions than those obtained using current method.

• 한국항공운항학회지
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• 제24권4호
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• pp.35-43
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• 2016

UAV has been promoted for practical use in the field of civilian and military. Recently, UAV is required high-specification performance such as long-term flight and precision observation. Among these UAVs, High Altitude Long Endurance UAV(HALE UAV) has been developed for the purpose to replace some of the functions of the satellite such as meteorological observation, communications and internet relay while flying a long period in the stratosphere. In order to fly a long period in harsh environment of the stratosphere, aircraft needs high Lift-Drag-Ratio and weight reduction of the structure. This paper performed the structural analysis for fuselage and empennage of HALE UAV. Critical loading conditions for structural analysis are acquired from flight load analysis and finally the results of structural sizing for weight reduction is presented.

• 한국해양공학회지
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• 제34권4호
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• pp.253-262
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• 2020

This study provides a comparative analysis of experiments-based enhancements and sensitivity evaluations for the structural design of an automatic ocean salt collector under various load conditions. The sizing variables of the structural members were considered as design factors. The strength and weight performances were selected as output responses. The design of experiments used in the comparative study consisted of the orthogonal array design, Box-Behnken design, and central composite design. The response surface model, one of the metamodels, was applied to the approximate model generation. The design enhancement performance metrics, including numerical costs and weight minimization, according to the design of experiments, were compared from the best design case results. The central composite design method showed the most enhanced design results for the structural design of the automatic ocean salt collector.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.311-314
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• 2008

The volume and size of the wind turbine gearbox has been increased with increasing transmitted power. The optimal sizing of gearbox is important due to limited space on the nacelle. The power-split type planetary gear train has been regarded as a better solution than conventional type from the point of view of the volume and weight. The purpose of this paper is to optimize the volume and weight of the gearbox by the analysis of structural characteristics and evaluation of strength of the power-split type planetary gear train.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.81-87
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• 1998

In this paper, a global acoustic design sensitivity analysis (DSA) of field point pressure with respect to structural sizing design variables is developed. Firstly acoustic sensitivity is formulated and implemented numerically. And it is combined with continuum structural sensitivity to obtain the global acoustic, design sensitivity. For this procedure, GASA (global acoustic design sensitivity analyzer) has been developed. A half scale of automobile cavity model is considered in this paper. In order to confirm accuracy of the results of global acoustic DSA obtained by GASA, it is compared with the result of central finite difference method. In order to reduce computation time, Rayleigh approximated solution is evaluated and compared with the solution which used every nodal velocities. Also the acoustic optimization procedure is performed using design sensitivities. From these numerical studies, it can be shown that global acoustic DSA is a useful tool to improve acoustic problems.

• 한국기계가공학회지
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• 제19권5호
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• pp.27-37
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• 2020

Structural optimization problems with discrete design variables require more function calculations (or finite element analyses) than those in the continuous design space. In this study, a method to find an optimal solution in the discrete design of the truss structure is presented, reducing the number of function calculations. Because a continuous optimal solution is the Karush-Kuhn-Tucker point that satisfies the optimality condition, it is assumed that the discrete optimal solution is around the continuous optimum. Then, response values such as weight, displacement, and stress are predicted using approximate models-referred to as hybrid metamodels-within specified design ranges. The discrete design method using the hybrid metamodels is used as a post-process of the continuous optimization process. Standard truss design problems of 10-bar, 25-bar, 15-bar, and 52-bar are solved to show the usefulness of this method. The results are compared with those of existing methods.