• 한국정밀공학회지
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• 제20권6호
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• pp.113-122
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• 2003

Topology optimization is begun with layout optimization that is attributed to Rozvany and Prager of the 1960's. They claimed that structure was transformed into truss connecting all the nodes of finite element and optimized by control of its sectional modulus. But, this method is partial topology optimization. General layout optimal design appliable to continum structure was proposed by Bendsoe and Kikuchi in 1988. Topology optimization expresses material stiffness of structure into function of arbitrary variable. If this variable is 1, material exists but if this variable is 0, material doesn't exist. Therefore, topology optimization searches the distribution function of material stiffness for structure. There are a few researchs for simple engineering problem such as topology optimization of square plane structure or truss structure. So, This study applied to topology optimization of table liner for vertical roller mill that is the largest scale in the world. After table liner decreased by 20% of original weight, the structure analysis for first optimized model was performed.

• 대한기계학회논문집A
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• 제27권5호
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• pp.764-771
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• 2003

To control the motion generated by a compliant mechanism the design method using specified geometrical advantage is proposed. The optimization problem is formulated to minimize the difference between the specified and the current geometrical advantage of a mechanism and topology optimization is applied to determine the layout of a mechanism. The results of several test problems including a displacement converter design and a gripper design are compared with a multi-criteria model and show that the design of an accurate compliant mechanism with specified geometrical advantage can be obtained.

• Composites Research
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• 제29권6호
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• pp.347-352
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• 2016

적층 복합재료 주름판에 대한 진동특성을 이론적 방법을 이용하여 분석하였다. 고려된 주름 형상은 사다리꼴을 기본으로 삼각형, 사각형 및 요각 사다리꼴형이다. 3차원 주름 구조물을 해석적으로 기계적 거동을 표현하는 것이 매우 어렵기 때문에 본 해석에서는 주름판의 진동특성을 분석하기 위해 등가균질모델을 적용하였다. 이를 위해 단위 주름을 직교이방성재료로 등가시켰으며, 해석에서 등가 신장 강성 및 굽힘 강성이 모두 고려되었다. 이론해석 결과의 타당성을 검증하기 위해 셸요소를 적용한 3차원 유한요소해석을 수행하였으며, 두 방법을 이용해 얻은 고유진동수 및 진동형상을 비교하였다. 주름판의 기하형상에 따른 영향을 분석하기 위해 다양한 수치예가 제시되었다.

• 대한기계학회논문집A
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• 제30권9호
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• pp.1102-1109
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• 2006

In this paper, the polarization of piezoelectric materials is considered to improve actuation since the piezoelectric polarization has influences on the performance of the actuator. The topology design of compliant mechanism can be formulated as an optimization problem of material distribution in a fixed design domain and continuous approximation of material distribution (CAMD) method has demonstrated its effectiveness to prevent the numerical instabilities in topology optimization. The optimization problem is formulated to maximize the mean transduction ratio subject to the total volume constraints and solved using a sequential linear programming algorithm. The effect of CAMD and the performance improvement of actuator are confirmed through Moonie actuator and PZT suspension design.

• Structural Engineering and Mechanics
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• 제33권4호
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• pp.429-446
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• 2009

Three-scale homogenization procedure is proposed in this paper to provide estimates of the effective thermal conductivities of porous carbon-carbon textile composites. On each scale - the level of fiber tow (micro-scale), the level of yarns (meso-scale) and the level of laminate (macro-scale) - a two step homogenization procedure based on the Mori-Tanaka averaging scheme is adopted. This involves evaluation of the effective properties first in the absence of pores. In the next step, an ellipsoidal pore is introduced into a new, generally orthotropic, matrix to make provision for the presence of crimp voids and transverse and delamination cracks resulting from the thermal transformation of a polymeric precursor into the carbon matrix. Other sources of imperfections also attributed to the manufacturing processes, including non-uniform texture of the reinforcements, are taken into consideration through the histograms of inclination angles measured along the fiber tow path together with a particular shape of the equivalent ellipsoidal inclusion proposed already in Sko ek (1998). The analysis shows that a reasonable agreement of the numerical predictions with experimental measurements can be achieved.

• 소성∙가공
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• 제23권3호
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• pp.171-177
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• 2014

The current collector for the molten carbonate fuel cell (MCFC) which has sheared protrusions is manufactured by the three-stage forming process that integrates slitting, preforming and final forming. Due to the repetition of sheared protrusions, an effective simulation method is required to predict the mechanical behavior. In the current study, a sheet with sheared protrusions was assumed to be an orthotropic plate, which has the same length, width and height. FEM simulations were conducted to evaluate the homogenized properties of the current collector, which has 4 (longitudinal direction) x 4 (transverse direction) sheared protrusions. The simulation model was constructed using hexahedral mesh coarsening. From the verification examples, it was found that the proposed simulation method was efficient within reasonable accuracy. The calculated homogenized properties can be applied to the design of a stack for molten carbonate fuel cells and the prediction of mechanical behavior for other applications.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1413-1418
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• 2003

In this study, the topology optimization is applied to the design of a piezoelectric microactuator satisfying the specific mean transduction ratio(MTR). The optimization problem is formulated to minimize the difference between the specified and the current mean transduction ratio. In order to analyze the response of the piezoelectric-structure coupled system, both the structural and the electric potential are considered in the finite element method. The optimization problem is resolved by using Sequential Linear Programming(SLP) and the results of test problems show that the design of a piezoelectric microactuator with specified mean transduction ratio can be obtained.

• 대한기계학회논문집A
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• 제28권2호
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• pp.206-213
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• 2004

In this study, the topology optimization is applied to the design of a piezoelectric microactuator satisfying the specific mean transduction ratio(MTR). The optimization problem is formulated to minimize the difference between the specified and the current mean transduction ratio. In order to analyze the response of the piezoelectric-structure coupled system, both the structural and the electric potential are considered in the finite element method. The optimization problem is resolved by using Sequential Linear Programming(SLP) and the results of test problems show that the design of a piezoelectric microactuator with the specified mean transduction ratio can be obtained.

• Journal of Mechanical Science and Technology
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• 제14권3호
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• pp.306-313
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• 2000

The homogenization method and the density function method are common approaches to evaluate the equivalent material properties for design cells composed of matter and void. In this research, using a new topology optimization method based on the homogenized material with a penalty factor and the chessboard prevention strategy, we obtain the optimal layout of a structure for the natural frequency of a designated mode. The volume fraction of nodes of each finite element is chosen as the design variable and a total material usage constraint is imposed. In this paper, the subspace method is used to evaluate the eigenvalue and its corresponding eigenvector of the structure for the designated mode and the recursive quadratic programming algorithm, PLBA algorithm, is used to solve the topology optimization problem.

• 한국해양환경ㆍ에너지학회지
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• 제19권3호
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• pp.194-202
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• 2016

본 연구에서는 10 MW급 부유식 파력-풍력 복합발전 시스템의 플랫폼 초기 개념설계를 위해 유한요소해석 기반 위상 최적화를 검토하였다. 실제 파력-풍력 복합발전 시스템 플랫폼의 위상최적화를 수행하기 전에 단순화된 구조설계 문제를 이용하여 효율적인 위상최적화 이론을 확인하고자 밀도법과 균질화설계법의 두 가지 위상최적화 이론을 적용하였다. 단순화된 설계 문제의 결과로부터 균질화설계법 이론을 파력-풍력 복합발전 시스템의 플랫폼 위상최적화에 적용하였다. 파력-풍력 복합발전 시스템의 플랫폼 개념설계를 위해서 유한요소해석 모델을 생성하고 설치해역의 해양환경하중을 고려하여 구조해석을 수행하였다. 설계파 및 조류와 같은 해양환경하중으로부터 기인하는 플랫폼 상의 압력과 계류삭의 인장력을 산출하기 위하여 동수력학 해석을 수행하였다. 구조해석을 위한 하중조건은 부유체 동수력학 해석으로부터의 결과와 파력-풍력 복합발전 시스템 중량을 고려하였고, 경계조건은 관성제거법을 사용하여 구현하였다. 밀도법 기반 파력-풍력 복합발전 시스템 플랫폼의 위상최적화 결과로부터 개념설계 단계에서 주요 구조부재의 배치방안을 제시하였다. 본 연구결과로부터 위상최적화는 부유식 파력-풍력 복합발전 시스템과 같은 새로운 형식의 해양구조물 개발에 있어서 주요 구조부재 배치의 개념설계에 대해 유용한 설계도구임을 확인하였다.