• Title/Summary/Keyword: Shape design sensitivity

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Shape Design Sensitivity Analysis of Axisymmetric Thermal Conducting Solids Using Boundary Integral Equations (경계적분방정식을 이용한 축대칭 열전도 고체의 형상설계민감도 해석)

  • 이부윤
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.1
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    • pp.141-152
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    • 1993
  • A generalized method is presented for shape design sensitivity analysis of axisymmetric thermal conducting solids. The shape sensitivity formula of a general performance functional arising in shape optimal design problem is derived using the material derivative concept and the adjoint variable method. The method for deriving the formula is based on standard axisymmetric boundary integral equation formulation. It is then applied to obtain the sensitivity formulas for temperature and heat flux constraints imposed over a small segment of the boundary. To show the accuracy of the sensitivity analysis, numerical implementations are done for three examples. Sensitivities calculated by the presented method are compared with analytic sensitivities for two examples with analytic solutions, and compared with sensitivies by finite difference for a cooling fin example.

Shape Design Optimization of Structure-Fluid Interaction Problems using NURBS Surfaces (NURBS 곡면을 이용한 구조-유체 연성문제의 형상 최적설계)

  • Jang, Hong-Lae;Kim, Min-Geun;Cho, Seon-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.508-511
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    • 2010
  • 본 논문에서는 정상상태 유체-구조 연성문제를 연속체 기반으로 정식화하고 유한요소법을 이용하여 완전 연성된 해를 구하였다. 대 변형을 고려하기 위하여 토탈 라그란지안 정식화를 사용하였으며 유체 및 구조의 비선형성이 고려되었다. 유체와 구조 영역의 형상을 NURBS 곡면을 이용하여 매개화하여 표현하였으며, 형상 최적화를 위해 효율적인 설계민감도 해석법인 애조인 기법을 이용하여 압력, 속도, 변위 등에 대한 설계민감도를 구하였다. 이를 이용하여 최소 컴플라이언스를 갖게 하는 구조물 내부의 유체영역의 설계 등의 수치예제를 통하여 개발된 방법론의 타당성을 확인하였다.

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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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A study on the improvement of shape design sensitivity in eigenvalue problems using semi-analytical method (반해석적 방법을 이용한 고유치 문제의 형상 설계 민감도 향상에 관한 연구)

  • 김현기;조맹효
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.159-166
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    • 2001
  • Structural optimization often requires the evaluation of design sensitivities. The Semi Aanalytic method(SAM) for computing sensitivity is popular in shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements, the SA method shows severe inaccuracy. In this paper, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover, the error of the SA method caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms. Finally, this paper shows that the refined SA method including the iterative method improves the results of sensitivity analysis in dynamic problems.

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The Energy Release Rate for Cracks in a Rotating Continuum (균열을 내재한 회전체의 에너지방출률)

  • 이태원
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.2
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    • pp.330-337
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    • 1995
  • For a rotating body with cracks, the new energy release rate equation is presented. The derived equation is different from the other researcher's results. It is a path-independent integral which excluded the derivatives of displacements near the crack tip, thereby improving the numerical accuracy of the energy release rate computation. Moreover, as the equation was derived on basis of the energy principle and non-linear elasticity without assumptions, it can applied to the cracked body with arbitrary shape under elastic-plastic deformation. Several examples are treated to demonstrate the efficiency and accuracy of the proposed method compared to existing methods.

Optimum Shape Design of a Rotating-Shaft Using ESO Method ESO 법을 이용한 회전축의 형상최적화

  • Yang, Bo-Suk;Kim, Yong-Han
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.360-364
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    • 2001
  • 본 논문에서는 최근의 진화적 구조최적화(ESO) 전략을 회전축의 형상최적화에 적용하였으며, 각 계산 스텝마다 단위 유한요소의 크기를 변경함으로써 기존의 방법보다 빠르고 정확한 최적형상에 수렴하는 새로운 방법을 제시하였다. 축요소의 직경을 시스템 설계변수로 하였으며, 축중량의 감소, 공진배율(Q-factor)의 감소 및 충분한 위험속도의 분리여유를 갖도록 목적함수를 설정하였다. 불평형응답 및 굽힙응력의 구속조건을 부가하였으며, 목적함수에 대한 설계변수의 감도해석을 수행하였다. 전동기축계에 대한 적용 결과로부터 주파수와 동적 구속조건하의 로터베어링 시스템에 대한 축 형상 최적화에 ESO법이 효과적으로 이용될 수 있음을 확인하였다.

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Shape Optimization of Piezoelectric Materials for Piezoelectric-Structure-Acoustic System (압전-구조-음향 연성계의 압전 액츄에이터 최적설계)

  • Wang, Se-Myung;Lee, Kang-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1627-1632
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    • 2000
  • Recently, piezoelectric materials have attracted considerable attention because of its self-sensing and actuating properties. To model smart structures, numerical modeling of structures with piezoelectric devices is essential. As many factors affect the performance of smart structures, optimization of these parameters is necessary. In this paper, the shape design sensitivity analysis of the 3D piezoelectric and structural elements is developed and shape optimization is performed. For the evaluation of the sensitivity, the finite element method is used. For the shape sensitivity, the domain velocity field is calculated. An acoustic cavity model is presented as a numerical example to study the feasibility of the formulation. The continuum sensitivity is compared with the results of the finite difference method by ANSYS. And the sequential linear programming (SLP) algorithm is used as the optimization algorithm.

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Sensitivity and optimisation procedures for truss structures under large displacement

  • Bothma, A.S.;Ronda, J.;Kleiber, M.
    • Structural Engineering and Mechanics
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    • v.7 no.1
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    • pp.111-126
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    • 1999
  • The work presented here focuses on the development of suitable discretised formulations, for large-displacement shape and non-shape design sensitivity analysis (DSA), which enable the straightforward incorporation of structural optimisation into established finite element analysis (FEA) codes. For the generalised displacement-based functional the design sensitivity vector has been expressed in terms of displacement sensitivity. The Total Lagrangian formulation is utilised for modelling of large deformation of truss structures. The variational formulation of the sensitivity analysis procedure is discretised by using "pseudo" - finite elements, Results are presented for the sensitivity analysis and optimisation of standard truss structures. For the purposes of this work, the analysis and optimisation procedures outlined below are incorporated into the FEA code ABAQUS.

Shape Optimal Design of Elastic Concrete Dam (탄성콘크리트 댐의 모양최적설계)

  • Yoo, Yung Myun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.5 no.4
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    • pp.9-14
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    • 1985
  • In this research mass of a plane strain two dimensional elastic concrete dam under gravitational and hydrostatic loads is minimized, through shape optimization of the dam cross section. Cross sectional area of the dam is taken as cost function of the optimization problem while constraints on the principal stress distribution and dam thickness are imposed. Shape of the boundary of the model is chosen as design variable. Variational formulation of the optimization problem, the material derivative idea of continuum mechanics, and an adjoint variable method are employed for the shape design sensitivity calculation. Then the gradient projection algorithm is utilized to obtain an optimum design iteratively. Research results fully demonstrate that the theory and procedure adopted are quite efficient and can be applicable to a wide class of practical elastic structural design problems.

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Shape Design Optimization of Fluid-Structure Interaction Problems (유체-구조 연성 문제의 형상 최적설계)

  • Ha, Yoon-Do;Kim, Min-Geun;Cho, Hyun-Gyu;Cho, Seon-Ho
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.2
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    • pp.130-138
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    • 2007
  • A coupled variational equation for fluid-structure interaction (FSI) problems is derived from a steady state Navier-Stokes equation for incompressible Newtonian fluid and an equilibrium equation for geometrically nonlinear structures. For a fully coupled FSI formulation, between fluid and structures, a traction continuity condition is considered at interfaces where a no-slip condition is imposed. Under total Lagrange formulation in the structural domain, finite rotations are well described by using the second Piola-Kirchhoff stress and Green-Lagrange strain tensors. An adjoint shape design sensitivity analysis (DSA) method based on material derivative approach is applied to the FSI problem to develop a shape design optimization method. Demonstrating some numerical examples, the accuracy and efficiency of the developed DSA method is verified in comparison with finite difference sensitivity. Also, for the FSI problems, a shape design optimization is performed to obtain a maximal stiffness structure satisfying an allowable volume constraint.