Papers by Author: Seok Yoon Han

Paper TitlePage

Authors: Jong Duk Chung, Seok Yoon Han, Hong Jung Chun
Abstract: Engineering safety diagnosis of crashed subway electric multiple units (EMUs) was conducted for safety assessment. Several advanced engineering analysis techniques including nondestructive evaluation (NDE) techniques and stress and structural analyses programs, were performed for better understandings and exploration of failure analysis and safety concerns. NDE techniques such as ultrasonic testing and magnetic particle testing, were used to detect manufacture-induced and/or in-service defects and collision-induced flaws, and measure the dimensions of deformed and non-deformed parts on damaged EMUs due to a rear-end collision. Moreover, stress and structural analyses using commercial I-DEAS software provided important information on stress distribution and load transfer mechanisms as well as the amount of damages during the crash. A good agreement has been found between structural analysis results and the results of actual damages in EMUs during crash. In this investigation, various advanced engineering analysis techniques for the safety analysis of subway EMUs have been introduced and the analysis results have been used to provide the critical information for the safety assessment of crashed EMUs.
114
Authors: Jae Kyoo Lim, Seok Yoon Han
Abstract: In order to analyze beam structures more accurately and effectively, a two-node orthotropic beam element is proposed. This beam element is formulated using a consistent higher order deformation theory of orthotropic beams of which the transverse normal deformation can be effectively estimated. The stiffness matrix and the vector of equivalent nodal forces of the beam element are derived explicitly by the Galerkin method. In order to examine the reliability and the characteristics of the beam element, the analytical and the finite element solutions of a simple cantilevered beam are compared with each other. As a result, the following conclusions are obtained; (1) the accuracy of the suggested orthotropic beam element is very excellent and so the transverse normal deformation and shear stress of an orthotropic beam can be effectively estimated. (2) It can be used for accurately analyzing the general beam structures regardless of the Euler's or the Timoshenko's beam.
519
Authors: Seok Yoon Han, M.N.L. Narasimhan, T.C. Kennedy
343
Authors: Seok Yoon Han, J.O. Kim, J.Y. Park, Byung Ju Yi, G.B. Chung
Abstract: Ultra-precision positioning systems basically require high natural frequency and sufficient workspace. To cope with this requirement, flexure hinge mechanisms have been proposed. However, previous designs have difficulty satisfying the functional requirements of the system due to problems in the modeling and optimization process since they are coupled. Therefore, this paper performs optimum design of a planar 3-D ultra-precision positioning mechanism using a booster based on axiomatic design. Based on preliminary kinematic analysis and dynamic modeling of the system, an optimum design is conducted. To examine the effectiveness of the optimal parameters obtained by a theoretical approach, a simulation is performed by FEM. The simulation result shows that a natural frequency of 200.53Hz and a workspace of 200 μm x 200 μm can be ensured, which is in very close agreement with the specified goal of design.
667
Authors: Seok Yoon Han, J.S. Maeng, S.H. Kim, J.Y. Park
Abstract: Parameter optimization of a static micro-mixer with a cantilever beam was accomplished for maximizing mixing efficiency using a sequential approximate optimization method. The objective function and design variables were chosen as mixing index, and the length and the angle measured from the horizontal of the cantilever beam, respectively. The Optimization problem of the mixer was considered as a series of sub-problems. Approximation to solve the sub-problems was performed by response surface methodology. To verify the reliability and the accuracy of the approximated objective function, ANOVA table and variable selection method were implemented, respectively. It was verified that the sequential approximate optimization method worked very well, and the mixing efficiency was significantly improved compared with the initial design.
471
Authors: Seok Yoon Han, S.S. Bae, S.J. Jung
Abstract: The growth-strain method was applied to cutout optimization in laminated composite plates. Since the growth-strain method optimizes a shape by generating the bulk strain to make the distributed parameter uniform, the distributed parameter was chosen as Tsai-Hill value. In this study, of particular interest is to see whether the growth-strain method developed for shape optimization in isotropic media would work for laminated composite plates. In volume control of the growth-strain method, it makes Tsai-Hill value at each element uniform in laminated composite plates under the predetermined volume. The shapes optimized by Tsai-Hill fracture index were compared with those of the initial shapes for the various load conditions and predetermined volumes of laminated composite plates. As a result, it was verified that volume control of the growth-strain method worked very well for cutout optimization in laminated composite plates.
833
Authors: Seok Yoon Han, J.Y. Park, Y.J. Ma
Abstract: Stress control of the growth-strain method was applied to shape optimization of multiple cutouts in laminated composite plates. Since the growth-strain method optimizes a shape by generating the bulk strain to make the distributed parameter uniform, the distributed parameter was chosen as Tsai-Hill value, as volume control of the growth-strain method. In this study, of particular interest is to see whether stress control of the growth-strain method developed for shape optimization in isotropic media would work for laminated composite plates. The shapes optimized by Tsai-Hill fracture index were compared with those of the initial shapes for the various load conditions. As a result, it was verified that stress control of the growth-strain method also worked very well for multiple cutouts optimization in laminated composite plates.
839
Authors: Seok Yoon Han
Abstract: Shape optimization a cantilevered beam in mixed mode for prolonging fatigue life was accomplished by the linear elastic fracture mechanics and the growth-strain method. Linear elastic fracture mechanics (LEFM) was used to evaluate the stress intensity factor and fatigue life. The growth-strain method was used to optimize a shape. From the results, it was found that the optimal shape of a cantilevered beam greatly prolongs their fatigue life, and the growth-strain method is an appropriate technique for shape optimization of a structure having a crack.
827
Authors: Seok Yoon Han, Y.J. Ma, J.Y. Park
Abstract: Shape optimization was performed to obtain the precise shape of cutouts including the internal shape of cutouts in laminated composite plates by three dimensional modeling using solid element. The volume control of the growth-strain method was implemented and the distributed parameter was chosen as Tsai-Hill failure index for shape optimization. In order to verify the validity of the obtained optimal shapes, the changes of the maximum Tsai-Hill failure index were examined for each load condition and cutouts. The following conclusions were obtained in this study; 1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in anisotropic laminate composite, 2) The optimal three dimensional shapes of the various load conditions and cutouts were obtained, 3) The maximum Tsai-Hill failure index was reduced up to 68% when shape optimization was performed under the initial volume by volume control of growth-strain method.
2740
Showing 1 to 9 of 9 Paper Titles