• 대한기계학회논문집A
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• 제38권6호
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• pp.619-627
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• 2014

본 논문은 등가정하중을 이용하여 제어시스템을 포함한 구조물의 설계를 위한 최적화 방법을 제안한다. 지난 연구는 구조물과 제어시스템 최적설계를 독립적으로 분리하여 수행하였고, 구조물과 제어시스템을 동시에 최적화하여도 제어시스템의 제어변수는 정상상태에서만 최적화하여 성능을 향상시켰다. 하지만 제어변수는 모든 시간영역에서 최적화해야 한다. 즉, 제어시스템의 해석은 과도상태에서 수행해야 한다. 본 연구에서는 새로운 등가정하중을 이용하여 제어변수를 포함하는 제어시스템 구조물의 최적설계를 위한 방법을 제시하였다. 등가정하중은 동적하중이 구조물에 작용할 때 발생하는 임의 시간에서의 변위장과 동일한 변위장을 만들어내는 정하중을 의미한다. 이렇게 계산된 등가정하중을 이용하여 설계영역에서 선형정적응답 최적설계를 진행한다. 몇 가지 예제를 통해 새로운 등가정하중을 적용한 동적응답 최적설계방법의 유용성을 확인하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 제 25회 정기총회 및 추계학술발표회
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• pp.51-58
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• 2000

The purpose of this study is the optimum modification of dynamic characteristics of stiffened plate structure. In the method of the optimization ,finite element method (FEM), sensitivity analysis and optimum structural modification method are used. To begin with, using FEM, the dynamic characteristics of stiffened plate structure is analyzed. Next, rate of change of dynamic characteristic by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of plate and cross section moment become a design variable. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure.

• Smart Structures and Systems
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• 제6권7호
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• pp.867-887
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• 2010

An energy-based variational approach is used for structural dynamic modeling of the IPMC (Ionic Polymer Metal Composites) flapping wing. Dynamic characteristics of the wing are analyzed using numerical simulations. Starting with the initial design, critical parameters which have influence on the performance of the wing are identified through parametric studies. An optimization study is performed to obtain improved flapping actuation of the IPMC wing. It is shown that the optimization algorithm leads to a flapping wing with dimensions similar to the dragonfly Aeshna Multicolor wing. An unsteady aerodynamic model based on modified strip theory is used to obtain the aerodynamic forces. It is found that the IPMC wing generates sufficient lift to support its own weight and carry a small payload. It is therefore a potential candidate for flapping wing of micro air vehicles.

• Structural Engineering and Mechanics
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• 제43권6호
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• pp.711-724
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• 2012

The goal of this study is to conceptually orientate optimized layouts of outrigger belt trusses which are in widespread use today in the design of tall buildings by strut-and-tie truss models utilizing a topology optimization method. In this study unknown strut-and-tie models are realized by using a typical SIMP method of topology optimization methods. In tradition strut-and-tie model designs find the appropriate strut-and-tie trusses along force paths with respect to elastic stress distribution, and then engineers or designers determine the most proper truss models by experience and intuition. It is linked to a trial-and-error procedure based on heuristic strategies. The presented strut-and tie model design by using SIMP provides that belt truss models are automatically and robustly produced by optimal layout information of struts-and-ties conforming to force paths without any trial-and-error. Numerical applications are studied to verify that outrigger belt trusses for tall buildings are optimally chosen by the proposed method for both static and dynamic responses.

• 대한기계학회논문집A
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• 제36권6호
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• pp.699-705
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• 2012

안전벨트의 역할은 차량 충돌이 발생했을 때 운전자를 보호하는 것이다. 그러나 강한 충돌이 발생하게 되면 운전자가 안전벨트에서 미끄러지게 되어 강한 충격을 받는다. 그러므로 이러한 현상을 방지하기 위해 새로운 안전벨트의 개발이 필요하다. 이 연구에서는 새로운 개념의 안전벨트인 Dynamic Locking Tongue(DLT)을 개발하였다. DLT장치는 강한 충돌이 발생했을 때 벨트(Webbing)가 안전벨트에서 미끄러지지 않게 하여 운전자의 피해를 줄여주는 장치이다. DLT장치 개발은 동역학 해석 프로그램인 SAMCEF를 이용하였다. 우선 DLT장치의 유한요소모델을 생성하였다. 그리고 실제 시험방법과 유사한 환경을 만들어 테스트를 해보았다. 이를 통해 DLT장치의 무게와 응력를 구할 수 있다. DLT장치의 최소 강도와 무게를 구하기 위해 반응 표면 분석법을 이용하여 DLT장치의 형상을 최적화하였다. 최적화된 DLT장치를 구조 해석을 통해 신뢰성을 검증하였다.

• 전산구조공학
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• 제10권2호
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• pp.233-242
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• 1997

이 논문은 연속보의 동적 최적설계에 관한 연구이다. 본 연구에서는 연속보의 근사적인 최적제원을 결정하기 위하여 컴퓨터 프로그램의 실행결과를 이용한 기법을 이용하였다. 경간길이, 질량 및 휨강성이 변화하는 연속보의 자유진동해석과 이동 집중하중이 작용하는 경우 동적응답해석을 실행할 수 있는 컴퓨터 프로그램을 개발하였다. 모형실험 결과와 이론적인 해석결과가 잘 일치하여 해석결과의 타당성을 검증할 수 있었다. 설계효율을 나타내기 위하여 최대 동적응력, 경간사이의 응력차이, 이동 집중하중이 작용하는 점에서의 rms 처짐 및 전체지간의 총질량 등 4가지의 무차원 변수들의 선형결합으로 이루어지는 최적함수를 정의하였다. 3경간 연속보에 대한 해석결과 개략적인 최적제원을 갖는 연속보로 설계하는 경우 등간격의 등단면 연속보에 비해 설계효율을 개선할 수 있음을 알 수 있었다.

• 한국생산제조학회지
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• 제18권4호
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• pp.337-347
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• 2009

Generally, finite element models used in structural analysis have some uncertainties of the geometric dimensions, applied loads and boundary conditions, as well as in material properties due to the manufacturability of aluminum intensive body. Therefore, it is very important to refine or update a finite element model by correlating it with dynamic and static tests. The structural optimization problems of automotive body are considered for mechanical structures with initial stiffness due to preloading and in operation condition or manufacturing. As the mean compliance and deflection under preloading are chosen as the objective function and constraints, their sensitivities must be derived. The optimization problem is iteratively solved by a sequential convex approximation method in the commercial software. The design variables are corrected by the strain energy scale factor in the element levels. This paper presents an updated method based on the sensitivities of structural responses and the residual error vectors between experimental and simulation models.

• Computational Structural Engineering : An International Journal
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• 제1권2호
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• pp.89-96
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• 2001

A study on the topology optimization of a Hard-Disk-Driver(HDD) actuator arm is presented. The purpose of the present wert is to increase the natural frequency of tole first lateral mode of the HDD actuator arm under the constraint of total moment of inertia, so as to facilitate the position control of the high speed actuator arm. The first lateral mode is an important factor in the position control process. Thus the topology optimization for 2-D model of the HDD actuator arm is considered. A new objective function corresponding to multieigenvalue optimization is suggested to improve the solution of the eigenvalue optimization problem. The material density of the structure is treated as the design variable and the intermediate density is penalized. The effects of different element types and material property functions on the final topology are studied. When the problem is discretized using 8-node element of a uniform density, tole smoothly-varying density field is obtained without checker-board patterns incurred. AS a result of 7he study, an improved design of the HDD actuator arm is suggested. Dynamic characteristics of the suggested design are compared computationally with those of the old design. With the same amount of the moment of inertia, the natural frequency of the first lateral mode of the suggested design is subsequently increased over the existing one.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.276-284
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• 1998

Optimum design of bumper beam is investigated using nonlinear CAE structural analysis techniques.In order to minimize its weight, while enhancing structural performances, bumper beam structural analyses were carried out to produce optimum section. Model is composed of bumper beam and stay. First, considering FMVSS safety standard, static strength and energy absorbing capability were estimated for several competitive bumpers through pendulum static analysis, and most promising section was chosen. Next, to ensure dynamic crashworthinesss performance for center pole impact was evaluated for the bumper beam with chosen section through pendulum static analysis, referring to DHS bumper dynamic impact standard. Finally, 2.5 mph bumper beam was designed and its structural performance was estimated. Through this investigation, an optimized bumper beam section with less weight of 20% while maintaining almost equal carshworthiness, compared with a conventional bumper beam section which proved its impact crashworthiness by experiments, was developed.

• 전기학회논문지
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• 제65권6호
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• pp.1045-1051
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• 2016

This paper introduces a new optimal design method using a bacterial survival strategies for a ectromagnet of Maglev transportation vehicle. Usually, an electromagnetic suspension which has more advantages than electro dynamic suspension is used in Maglev systems. However, the structural constraints must be considered in the optimal design of an electromagnet for electromagnetic suspend system. In this paper, the optimal design method of a electromagnet based on a bacterial survival strategies optimization algorithm to design the electromagnet satisfying the structural constraints. The effectiveness of the proposed method was verified by Matlab simulations and the simulation results show that the proposed method is more efficient than conventional methods.