• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.335-342
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• 2005

Using higher order Mindlin plates and piezoelectric materials, eigenvalue problems are considered. Since piezoelectric crystal resonators produce a proper amount of electric signal for a thickness-shear frequency, the objective is to decouple the thickness-shear mode from the others. Design variables are the bulk material densities corresponding to the mass of masking plates for electrodes. The design sensitivity expressions for the thickness-shear frequency and mode shape vector are derived using direct differentiation method(DDM). Using the developed design sensitivity analysis (DSA) method, we formulate a topology optimization problem whose objective function is to maximize the thickness-shear component of strain energy density at the thickness-shear mode. Constraints are the allowable volume and area of masking plate. Numerical examples show that the optimal design yields an improved mode shape and thickness-shear energy.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.584-593
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• 2016

In this study, an improvement design method for reducing the vibration of fenders equipped in a tractor is proposed through the establishment of a finite element model and the topology optimization. As the original shapes of the parts cannot be altered, an improved design model was derived in which a stiffener was attached to the border of parts. Thus, the first resonance frequency was increased by approximately 16 Hz, which was confirmed to be the frequency interval for avoiding the idle and operating frequency of the engine. Finally the improved design model was applied to confirm the effect of vibration reduction. Therefore, it can be concluded that the improved design model of the tractor fender is effective at reducing vibrations of the tractor fender.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.618-621
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• 2008

The magnetic recording system shows the difference of the magnetic recording density according to the direction of the magnetic field. The yoke shape of the recording system affects the magnetic field direction; therefore, the recording density may be raised by changing the shape. This paper intends not only to increase the magnetic flux density of the record region but also to reduce the recording loss of a specific region through the simultaneous design of the yoke and the magnet. The recording loss can be reduced by minimizing the magnetic flux of the adjacent area to the recording region. The topology optimization method is used to obtain the optimal shape both of the yoke and the magnet. And the commercial package, Maxwell is used to verify the result.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.651-652
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• 2006

This research presents a topology optimization for manipulating the main heat flow in coupled magneto-thermal systems. The heat generated by eddy currents is considered in the design domain assuming an adiabatic boundary. For a practical optimization, the convection condition is considered in the topological process of the thermal field. Topology design sensitivity is derived by employing the discrete system equations combined with the adjoint variable method. As numerical examples, a simple iron and a C-core design heated-up by eddy currents demonstrate the strength of the proposed approach to solve the coupled problem.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1017-1022
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• 2004

Though the standard element density-based topology optimization method has been applied for the optimal design of multiphysics systems, some theoretical problems, such as material interpolation, undershoot temperature prediction, and unstable elements, still remain to be overcome. The objective of this investigation is to present a new topology optimization formulation based on the element connectivity parameterization (ECP) in order to avoid the numerical problems in multiphysics system design and improve optimization results. To show the validity of the proposed approach, the designs of an optimal thermal dissipation and an electro-thermal-compliant actuator were considered.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.352-355
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• 2004

The objective of this work is to develop a new design method to find optimal coils, especially the optimal coil configuration of an optical pickup actuator. In designing actuator coils, the developed Lorenz force in the coils along the desired direction should be made as large as possible while forces and torques in other directions should be made as small as possible. The design methodology we are developing is a systematic approach that can generate optimal coil configurations for given permanent magnet configurations. To consider the best coil configuration among all feasible coil configurations, we formulate the design problem as a topology optimization of a coil. The present formulation for coil design is noble in the sense that the existing topology optimization is mainly concerned with the design of yokes and permanent magnets and that the optimization of actuator coils is so far limited within shape or size optimization. Though the present design methodology applies to any problem, the specific design example considered is the design of fine-pattern tracking and focusing coils.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1187-1193
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• 2006

Traditionally, the continuum-based topology optimization methods employing the SIMP technique have been used to design compliant mechanisms. Although they have been successful, the optimized mechanisms by the methods are usually difficult to manufacture because of their geometrical complexities. The objective of this study is to develop a topology optimization method that can produce easy-to-fabricate mechanism structure. The proposed method is a ground beam method where beam connectivity is controlled by the beam joint stiffness. In this approach, beam joint stiffness determines the mechanism configuration. Because b the ground structure beams have uniform thicknesses varying only discretely, the resulting mechanism topologies become easily manufacturable.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1029-1034
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• 2004

Recent engineering process requires fast development and manufacturing of the products. This paper mainly discusses the process of rapid product development (RPD) from the reverse engineering to the optimal design. A laser scanning system scans a product and the efficient data processing method reduces the scanned point data. The reduced (scanned) points model is transformed to a finite element model without the construction of a CAD model. Since CAD modeling is a time-consuming work, skipping this step can save much time. This FE model is updated from the result based on the structural characteristics from modal test of the real model. For FE model updating, Response Surface Method is adopted. Finally, the updated FE model is optimized using the reliability-based topology optimization, which is developed recently. All these processes are applied to the design of an upper part model of a cellular phone.

• 한국전산구조공학회논문집
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• 제28권5호
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• pp.441-449
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• 2015

본 논문에서는 커코프 판이론과 폰-칼만 비선형 변형율-변위 관계를 이용하여 서형화된 좌굴해석을 수행하였다. 평면응력과 좌굴문제에서 영률과 두께에 관한 설계민감도식을 유도하였고, 고유치를 최대화하면서 컴플라이언스를 최소화하는 위상최적설계 기법을 정식화하였다. 좌굴해석에서의 프리스트레스를 이용하여 판 좌굴문제에 적용할 수 있는 위상최적설계 기법을 개발하였다. 폰-칼만 비선형 변형률을 사용하여 좌굴문제의 응력행렬을 구성하는데 프리스트레스가 필요하므로 면외로의 운동을 도입하였다. 위상최적설계를 위하여 정규재료밀도를 설계변수로 하고, 목적함수는 최소 컴플라이언스와 최대 고유진동수로 하였으며 제한조건은 허용되는 재료량이다. 여러 수치예제를 통하여 개발된 설계민감도 해석법은 유한차분 민감도와 비교하여 매우 정확한 값을 가지고, 위상최적설계는 물리적으로 의미있는 결과를 제공함을 확인하였다.

• 전산구조공학
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• 제9권3호
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• pp.169-177
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• 1996

구조물에 있어서 위상학적 최적화 문제는 최적화를 구하는 과정에서 구조체가 변화함으로 인한 어려움 때문에 최적화 분야에서 가장 어려운 문제로 간주되어 왔다. 종래의 방법으로는 일반적으로 구조요소 사이즈가 영으로 접근할 때 강성 매트릭스의 singularity를 발생시킴으로써 최적의 해를 얻지 못하고 도중에 계산이 종료되어 버린다. 본 연구에 있어서는 이러한 문제점들을 해결하기 위한 비선형 프로그래밍 formulation을 제안하는 것을 목적으로 한다. 이 formulation의 주된 특성은 요소 사이즈가 영이 되는 것을 허용한다. 평형방정식을 등제약조건으로 간주함으로써 강성 매트릭스의 singularity를 피할 수 있다. 이 formulation을 하중을 받는 구조물에 있어서 응력과 변위의 제약조건하에서 중량을 최소화할때의 유한요소의 두께를 구하는 디자인 문제에 적용하여, 이 formulation이 위상학적 최적화에 있어서의 효과를 입증하였다.