• Title, Summary, Keyword: 형상 최적설계

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A study on shape optimization technique applied to weight-reduction design of aluminium vehicle structures (알루미늄 차체 경량화를 위한 형상최적설계기법의 적용에 대한 고찰)

  • 권태수
    • Proceedings of the KSR Conference
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    • pp.370-377
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    • 2002
  • 오늘날 차량의 경량화를 위해서 알루미늄 차체를 사용하는 것은 필수적인 결정처럼 되어버렸다. 차체에 사용되는 알루미늄 압출재의 형상은 아주 다양하게 제작이 가능하다. 그러나, 다양한 형상이 가능한 만큼 설계 엔지니어에게는 결정하기 어려운 문제가 되어버린다. 주어진 하중조건하에서 최적의 형상을 설계하는 방법을 찾는 것은 이제 알루미늄 차체의 사용이 보편화되어가는 시점에 매우 중요한 일이 된 것이다. 본 논문에서는 형상최적설계란 도구를 사용하여 압출재 형상을 설계하는 방법에 대한 가능성을 살펴보고자 한다. 몇 개의 간단한 예제를 통하여 가능성을 점검하였고, 분석을 통하여 몇가지 결론에 도달하였다.

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Level Set Based Topological Shape Optimization of Phononic Crystals (음향결정 구조의 레벨셋 기반 위상 및 형상 최적설계)

  • Kim, Min-Geun;Cho, Seon-Ho;Hashimoto, Hiroshi;Abe, Kazuhisa
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.693-696
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    • 2011
  • 본 논문에서는 레벨셋 방법을 이용하여, 소음을 차단하기 위한 음향 구조물의 형상 최적 설계를 수행하였다. 음향 결정 구조에서는 음향이 흩어져 있는 결정 구조에 의해서 굴절되기 때문에 결정 모양을 조정함으로써, 음향 거동을 제어 할 수 있다. 형상 최적 설계의 목적은 특정한 각도와 각속도로 입사되는 입사파에 대해서 음향 투과율(acoustic transmittance)이 최소가 되도록 음향 결정의 형상(inclusion shape)을 결정하는 것이다. 음향 압력(acoustic pressure)은 주기성을 갖는 음향 결정에 대해서 헬몰츠(Helmoltz)형태의 지배 방정식을 풀어서 얻을 수 있다. 본 연구에서는 음향 구조물로 결정이 수평 방향으로는 주기적으로 무한히 분포하고 수직방향으로는 유한한 층간 구조를 가지고 있는 소음 방어벽 (Noise barrier)을 고려한다. 결정의 위치는 고정되어 있고, 결정의 형상을 설계 변수로서 음파의 거동을 제어할 수 있도록 하였다. 주기적 구조물을 고려하기 때문에 결정의 좌와 우에 Bloch 이론을 적용해 주기적 경계조건을 부과하였고, 소음 방어벽 위와 아래에는 임피던스 행렬(impedance matrix)를 이용하여, 무한 균질 영역과 소음 방어벽사이의 음파 투과를 모사하였다. 복잡한 형상 변화를 표현하기 위해 임시적 경계를 이용한 레벨셋 방법을 사용하였다. 설계 민감도 해석을 통해 목적함수가 감소하는 방향으로 경계에서의 수직 벡터를 계산하고, 이를 헤밀턴-자코비(Hamilton-Jacob) 방정식에 대입하여, 최적의 형상을 나타내는 레벨셋 함수를 구하였다.

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Design Optimization of QTP-UAV Prop-Rotor Blade Using ModelCenter (ModelCenter를 이용한 QTP-UAV 프롭로터 블레이드 형상 최적설계)

  • Kang, Hee Jung
    • Journal of Aerospace System Engineering
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    • v.11 no.4
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    • pp.36-43
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    • 2017
  • Blade design optimization of QTP-UAV prop-rotor was conducted using ModelCenter(R). Performance efficiency of the blade in hover and forward flight were adopted as the multi-objective function. Required power and pitch link force applied to constraint in each flight mode and limited lower than the value of the baseline blade. Design variables of root chord length of the blade, taper ratio, twist slope, twist angle at 0.5R of the blade, anhedral angle, parabolic coefficient of a tip shape and location of airfoil were used to generate the blade planform. CAMRAD-II, the comprehensive analysis program of rotorcraft, was used for performance analysis of prop-rotor blade in design process. Performance of the optimized blade improved 1.6% of figure of merit in hover and 13.6% of propulsive efficiency in forward flight. Pitch link force also reduced approximately 30% less than that of the baseline blade.

Shape Generation and Optimization Technique of Space Frame Structures with Ellipse and Vault Complex Type (타원형 및 볼트복합형 스페이스 프레임 구조물의 형상 생성 및 최적화 방안)

  • Kim, Ho-Soo;Park, Young-Sin
    • Journal of the Korean Association for Spatial Structures
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    • v.10 no.4
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    • pp.113-122
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    • 2010
  • Space frame structures are included in the large spatial structures and can adopt various structure types. But, it is not easy to choose the optimal member size and shape because it depends on the structural engineer's experience and the repeated trial and error. Therefore, in this study, the final goal is to help the designer with the selection of the optimum shape. First, various space frame structures with ellipse dome and vault complex types are chosen and the shape generation method is considered to generate the nodes, coordinates and members. In optimal design process of space frame structure, each node coordinate changes according to height variation or the number of rings. Therefore, the auto generation technique of nodes and members is required in order to consider this phenomenon in optimal design process. Next, the shape generation module is created, base on the shape generation method. This module is connected with the analysis module and the optimization algorithm. Finally, the example model is presented for the evaluation of the efficiency of optimization algorithms.

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Shape Optimum Design of Cantilever with Weight and Journal Bearing Cap (자중을 고려한 외팔보와 저널 베어링 덮개의 형상 최적설계)

  • Lim, O-Kang;Lee, Jin-Suk;Cho, Heon;Lee, Byung-Woo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.12 no.3
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    • pp.427-435
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    • 1999
  • In the field of shape optimum design, much efforts are needed in regridding method and shape design sensitivity analysis. In this paper, Bezier curve is used to make the boundary of a structure and the improved direct differentiation method is used to calculate the shape design sensitivity. To regrid the finite element model, modified displacement field is presented in this paper. The modified displacement field makes more fine grid at large curvature. The purpose of this paper is to obtain the optimum shape of a cantilever with weight and a 3-dimensional journal bearing cap.

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Lightweight Crane Design by Using Topology and Shape Optimization (위상최적설계와 형상최적설계를 이용한 크레인의 경량설계)

  • Kim, Young-Chul;Hong, Jung-Kie;Jang, Gang-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.7
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    • pp.821-826
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    • 2011
  • CAE-based structural optimization techniques are applied for the design of a lightweight crane. The boom of the crane is designed by shape optimization with the shape of the cross section of the boom as the design variable. The design objective is mass minimization, and the static strength and dynamic stiffness of the system are set as the design constraints. Hyperworks, a commercial analysis and optimization software, is used for shape and topology optimization. In order to consistently change the shape of the elements of the boom with respect to the change in the shape of its cross section, the morphing function in Hyperworks is used. The support of the boom of the original model is simplified to model the design domain for topology optimization, which is discretized by using three-dimensional solid elements. The final result after shape and topology optimization is 19% and 17% reduction in the masses of the boom and support, respectively, without a deterioration in the system stiffness.

Isogeometric Shape Design Optimization of Structures Subjected to Design-dependent Loads (설계 의존형 하중 조건을 갖는 구조물의 아이소-지오메트릭 형상 최적설계)

  • Yoon, Min-Ho;Koo, Bon-Yong;Ha, Seung-Hyun;Cho, Seon-Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.1
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    • pp.1-7
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    • 2011
  • In this paper, based on an isogeometric approach, we have developed a shape design optimization method for plane elasticity problems subjected to design-dependent loads. The conventional shape optimization using the finite element method has some difficulties in the parameterization of geometry. In an isogeometric analysis, however, the geometric properties are already embedded in the B-spline basis functions and control points so that it has potential capability to overcome the aforementioned difficulties. The solution space for the response analysis can be represented in terms of the same NURBS basis functions to represent the geometry, which yields a precise analysis model that exactly represents the normal and curvature depending on the applied loads. A continuum-based isogeometric adjoint sensitivity is extensively derived for the plane elasticity problems under the design-dependent loads. Through some numerical examples, the developed isogeometric sensitivity analysis method is verified to show excellent agreement with finite difference sensitivity.

Isogeometric Shape Design Optimization of Power Flow Problems at High Frequencies (고주파수 파워흐름 문제의 아이소-지오메트릭 형상 최적설계)

  • Yoon, Minho;Ha, Seung-Hyun;Cho, Seonho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.27 no.3
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    • pp.155-162
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    • 2014
  • Using an isogeometric approach, a continuum-based shape design optimization method is developed for steady state power flow problems at high frequencies. In case the isogeometric method is employed to the shape design optimization, the NURBS basis functions used in CAD geometric modeling are directly utilized to embed the exact geometry into the computational framework so that the design parameterization for shape optimization is much easier than that in the finite element method and consequently provides the enhanced smoothness of design perturbations. Thus, exact geometric models can be used in both the response and the shape sensitivity analyses, where normal vector and curvature are continuous over the whole design space so that enhanced shape sensitivity can be expected. Through numerical examples, the developed isogeometric sensitivity is compared with finite difference one to provide excellent agreement. Also, it turns out that the proposed method works very well in the shape optimization problems.

Development of Technology for Optimized Wing Design of Subsonic Aircraft (아음속 항공기 날개 최적 설계 기술 개발)

  • Kim, Cheol-Wan;Choi, Dong-Hoon
    • Aerospace Engineering and Technology
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    • v.10 no.1
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    • pp.175-182
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    • 2011
  • Optimized design was performed for a subsonic aircraft wing. The subsonic aircraft is dual turbo-prop and carrying less than 100 passengers. The cruise speed is Mach 0.6. The design was performed by two stages. The first stage is to decide the height of horizontal tail by analyzing the directional stability with Vorstab and then, the optimized wing configuration was selected with Piano, a optimizer commercially available. Fluent, a commercial CFD software was utilized to predict the aerodynamic performance of the aircraft. Drag of the aircraft was minimized with maintaining constant lift for cruise. The optimization reduced 10 counts from the initial wing configuration.

Design Sensitivity Analysis and Optimization of Plane Arch Structures Using Variational Formulation (변분공식화를 이용한 2차원 아치 구조물의 설계민감도 해석 및 최적설계)

  • 최주호
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.14 no.2
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    • pp.159-171
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    • 2001
  • 평면 아치 구조물에 대해 선형 탄성 변분방정식에 기반을 둔 설계민감도 해석을 위한 일반적 이론을 개발하였다. 아치 구조물내의 임의 마디에 정의된 응력범함수를 고려하였고 이에 대한 설계민감도 공식을 유도하기 위해 전미분(material derivative) 개념과 보조(adjoint) 변수 방법을 도입하였다. 얻어진 민감도 공식은 구조해석 결과를 얻고 나면 이들로부터 단순 대수연산을 통해 계산이 되므로 적용이 간편할 뿐 아니라 해의 정확도가 높은 잇점이 있다. 본 방법은 아치의 형상을 매개변수를 통해 표현하므로 얕은 아치에 국한하지 않고 어떠한 형상도 고려가 가능하며, 나아가서 아치의 형상변화를 형상에 대해 수직뿐 아니라 접선방향도 포함하여 일반적으로 고려하므로 다양한 형상설계가 가능하다. 몇 가지 예제에서 민감도 계산을 수행함으로써 본 방법의 정확도와 효율성을 입증하였으며, 두 가지의 설계최적화 문제를 대상으로 실제로 두께 및 형상최적설계를 수행하였다.

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