http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Sensitivity analysis for fixed-grid shape optimization by using oblique boundary curve approximation
Jang, Gang-Won,Kim, Yoon Young Elsevier 2005 International journal of solids and structures Vol.42 No.11
<P><B>Abstract</B></P><P>The remesh-free property is the most attractive feature of the various versions of fixed-grid-based shape optimization methods. When the design boundary curves do not pass through the predetermined analysis grids, however, the element stiffness as well as the stress along the curves may be computed inaccurately. Even with the popular area-fraction-based stiffness evaluation approach, the whole optimization process may become quite inefficient in such a case. As an efficient alternative approach, we considered a stiffness matrix evaluation method based on the boundary curve approximation by piecewise oblique curves which can cross several elements. The main contribution of this work is the analytic derivation of the shape sensitivity for the discretized system by the fixed-grid method. Since the force term in the sensitivity equation is associated only with the elements crossed by the design boundary curve, we only need the design velocities of the intersecting points between the curve and the fixed mesh. The present results obtained for two-dimensional elasticity and Poisson’s problems are valid for both the single-scale standard fixed-grid method and the multiscale fictitious domain-based interpolation wavelet-Galerkin method.</P>
Jang, Gang-Won,Kim, Kyung Joo,Kim, Yoon Young John Wiley 2008 International Journal for Numerical Methods in Eng Vol.75 No.11
<P>The difficulty in the analysis of thin-walled beams by a beam theory comes from slowly decaying end effects associated with warping and distortion. However, a beam theory without considering such effects yields inaccurate solutions especially near beam ends. Numerical analysis using a higher-order beam theory capable of representing such effects is now available, but the analysis of a series of box beams connected by angled joints still remains an unsolved problem because of the lack of a matching condition at the joint. The objectives of this investigation are to develop a field-variable-matching technique at an angled joint through a higher-order beam theory and to implement it in the finite element formulation. Thin-walled box beams in consideration are assumed to be subject to out-of-plane bending and torsion. Thus, the minimization of three-dimensional displacement mismatch is used to relate the field variables at a joint intersection. The minimization condition turns out to represent coupling effects of different deformation kinematics such as torsion, bending, distortion and warping. Point-wise displacement matching is not possible with a higher-order beam theory. The validity of the proposed technique was verified by a finite element analysis using two-node higher-order beam elements applied to some benchmark problems. Copyright © 2008 John Wiley & Sons, Ltd.</P>
Discrete thickness optimization of an automobile body by using the continuous-variable-based method
Gang-Won Jang,Young-Min Choi,Gyoo-Jae Choi 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.1
Design optimization of an automobile body for dynamic stiffness improvement is presented. The thicknesses of plates consisting of a monocoque body of an automobile are employed as design variables for optimization whose objective is to increase the first torsional and bending natural frequencies. By allotting one design variable to each plate of the body, compared to previous works based on element-wise design variables, the design space of optimization can be reduced to a large extent. Because the present optimization is based on continuous-variable-based algorithms, considering manufacturability of the optimized result, the converged values of plate thicknesses should be approximated to commercially available discrete values. A new straightforward thickness discretization scheme considering design sensitivities and employing a subsequent reduced optimization problem is proposed. The validity of the proposed thickness discretization scheme is verified through numerical experiments.