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박강수,장수영,이응식,윤성기,Park, Kang-Soo,Chang, Su-Young,Lee, Eung-Shik,Youn, Sung-Kie 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.6
A study on the topology optimization of a multi-spectral camera for space-use is presented. The optimization is carried out under self-weight and polishing pressure loading. A multi-spectral camera for space-use experiences degradation of optical image in the space, which can not be detected on the optical test bench on the earth. An optical surface deformation of a primary mirror, which is a principal component of the camera system, is an important factor affecting the optical performance of the whole camera system. In this study, topology optimization of the primary mirror of the camera is presented. As an objective function, a measure of Strehl ratio is used. Total mass of the primary mirror is given as a constraint to the optimization problem. The sensitivities of the objective function and constraint are calculated by direct differentiation method. Optimization procedure is carried out by an optimality criteria method. For the light-weight primary mirror design, a three dimensional model is treated. As a preliminary example, topology optimization considering a self-weight loading is treated. In the second example, the polishing pressure is also included as a loading in the topology optimization of the mirror. Results of the optimized design topology for the mirror with various mass constraints are presented.
적응적 내부 경계 레벨셋 기반 위상최적화를 이용한 쉘 구조물의 경량화 설계
박강수(Kang-Soo Park),윤성기(Sung-Kie Youn) 대한기계학회 2007 大韓機械學會論文集A Vol.31 No.12
In the present work, topology optimization method using adaptive inner-front level set method is presented. In the conventional level set based topology optimization method, there exists an incapability for inner-front creation during optimization process. In this regard, as a new attempt to avoid and to overcome the limitation, an inner-front creation algorithm is proposed. In the inner-front creation algorithm, the strain energy density of a structure along with volume constraint is considered. Especially, to facilitate the inner-front creation process during the optimization process, the inner-front creation map which corresponds to the discrete valued function of strain energy density is constructed. In the evolution of the level set function during the optimization process, the least-squares finite element method (LSFEM) is employed. As an application to shell structures, the lightweight design of doubly curved shell and segmented mirror is carried out.
강성 완화를 통한 위상최적화의 안정성 향상에 관한 연구
박강수(Kang-Soo Park),윤성기(Sung-Kie Youn) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
In the present work, topology optimization based on the stiffness regularization is presented. Due to the overestimated stiffness in low-order finite elements, in the conventional topology optimization method, there exists the numerical instability such as the occurrence of checkerboard pattern. In this regard, in the present work, the finite element stiffness is regularized by employing the stabilized conforming nodal integration (SCNI) scheme. In order to investigate the stiffness regularization and to discretize the design domain, two-dimensional linear quadrilateral element is employed. As the optimization problem, the compliance minimization of two-dimensional structures subjected to the volume constrain is carried out. In the verification, the optimum topologies of illustrative examples are compared with the conventional result.
적응적 내부 경계를 갖는 레벨셋 방법을 이용한 쉘 구조물의 위상최적설계
박강수(Kang-Soo Park),윤성기(Sung-Kie Youn) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
A new level set based topology optimization employing inner-front creation algorithm is presented. In the conventional level set based topology optimization, the optimum topology strongly depends on the initial level set distribution due to the incapability of inner-front creation during optimization process. In the present work, an inner-front creation algorithm is proposed, in which the sizes, positions, and number of new inner-fronts during the optimization process can be globally and consistently identified. To update the level set function during the optimization process, the least-squares finite element method is employed. As demonstrative examples for the flexibility and usefulness of the proposed method, the level set based topology optimization considering lightweight design of 3D shell structure is carried out.
박강수(Kang-Soo Park),윤성기(Sung-Kie Youn) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Main objective of this research is to develop and implement a numerical procedure to guarantee stable convergence and hole creation of the level set based topology optimization method. To verify the proposed topology optimization procedure, several numerical examples are treated. From the results of verification process, the hole creation and the stable convergence are examined. In the optimization process, two dimensional elastic structure is considered. The objective function is selected as the compliance of a structure. As a constraint, the total volume (or area) of a structure is limited to be a certain value. The sensitivities of the objective function and the constraint are calculated by direct differentiation method.