• Design & Manufacturing
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• v.7 no.1
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• pp.11-18
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• 2013

This paper presents the plastic inhomogeneous deformation behavior of bimetal composite rods during the axisymmetric and steady-state extrusion process through a conical die. The rigid-plastic FE model considering frictional contact problem was used to analyze the co-extrusion process with material combinations of Cu/Al. Different cases of initial geometry shape for composite material were simulated under different conditions of co-extrusion process, which includes the interference and frictional conditions. The main design parameters influencing on deformation pattern are diameter ratio of the composite components and semi-die angle. Efforts are focused on the deformation patterns, velocity gradient, predicted forming load and the end distance through the various simulations. Simulation results indicate that there is an obvious difference of forming pattern with various diameter ratio and semi-die angle. The analysis in this paper is concentrated on the evaluation of the design parameters on the deformation pattern of composite rod.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.119-126
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• 1985

형상은 3차원이지만 2차원 문제로 이상화하여 해석할 수 있는 탄성구조물의 최적설계를 내연기관 연결봉(Connecting Rod)을 예제로 사용하여 진행하였다. 연결봉은 각 부위에서의 두께는 다르나 평면응력상태에 있다고 가정하였다. 연결봉의 질량을 최소화하기 위해 두께의 분포 및 2차원 모델 경계의 모양을 설계변수로 채택하였고 설계변수 및 응력치에 대한 제한조건을 적용하였다. 설계감도계수 계산을 위해 Variational Formulation, Material Derivative, Adjoint Variable이론을 도입하였고 최적화 방법으로는 Gradient Projection Method를 사용하였다. 최적설계 결과 현재 사용중인 연결봉 무게의 20%를 줄일 수 있음이 밝혀졌다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.697-701
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• 2012

Numerical modeling for a coke dry quenching process was developed and evaluated. The cokes had similar characteristics to a porous material, therefore, its quenching analysis was simplified as a cooling process of porous blocks. A uniform inlet temperature and constant properties of materials in the oven were also assumed. With given operating conditions, temperature profiles in the cokes were calculated and compared to the actual values. The calculated temperature gradient was high at the upper part of the coke flow and the cooling rate decreased as cokes came down to the exit port. The exit port temperature of cokes was similar to the measured value, however, temperature-dependent material properties and operating conditions must be considered to predict the temperature precisely. The calculated results could be applied to design a coke oven to produce high quality cokes.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.108-115
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• 2008

We designed optical systems for a mobile phone camera using a spherical SELFOC lens and an aspherical plastic lens. Since the radial index distribution gives an additional design parameter for optical design, an aspheric lens could be replaced by a spherical lens. The imaging performances of the design were compared with conventional 2P design composed of two aspherical plastic lenses. In the first stage of study, we designed 1GRIN 1P lenses by using commercially available SELFOC materials. But, the conventional 2P lenses had better performance than the 1GRIN 1P lenses. In the 1GRIN 1P designs, the performance depends on index variation of GRIN material, the larger variation gives the better performance. Hence, we tried to design by using fictitious GRIN materials which have large index variation. We found if the index variation could be increased to about 3 times that of currently available SELFOC materials, the 1GRIN 1P lens will have equivalent or better performance than the conventional 2P design.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.6
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• pp.351-356
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• 2022

In this paper, we present the regression analysis and design optimization for improving the permeability of 3D woven materials based on numerical analysis data. First, the parametric analysis model is generated with variables that define the gap sizes between each directional wire of the woven material. Then, material properties such as bulk modulus, thermal conductivity coefficient, and permeability are calculated using numerical analysis, and these material data are used in the polynomial-based regression analysis. The Pareto optimal solution is obtained between bulk modulus and permeability by using multi-objective optimization and shows their trade-off relation. In addition, gradient-based design optimization is applied to maximize the fluid permeability for 3D woven materials, and the optimal designs are obtained according to the various minimum bulk modulus constraints. Finally, the optimal solutions from regression equations are verified to demonstrate the accuracy of the proposed method.

• Steel and Composite Structures
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• v.18 no.1
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• pp.1-28
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• 2015

In this paper, the dynamic response of functionally gradient steel (FGS) composite cylindrical panels in steady-state thermal environments subjected to impulsive loads is investigated for the first time. FGSs composed of graded ferritic and austenitic regions together with bainite and martensite intermediate layers are analyzed. Thermo-mechanical material properties of FGS composites are predicted according to the microhardness profile of FGS composites and approximated with appropriate functions. Based on the three-dimensional theory of thermo-elasticity, the governing equations of motionare derived in spatial and time domains. These equations are solved using the hybrid Fourier series expansion-Galerkin finite element method-Newmark approach for simply supported boundary conditions. The present solution is then applied to the thermo-elastic dynamic analysis of cylindrical panels with three different arrangements of material compositions of FGSs including ${\alpha}{\beta}{\gamma}M{\gamma}$, ${\alpha}{\beta}{\gamma}{\beta}{\alpha}$ and ${\gamma}{\beta}{\alpha}{\beta}{\gamma}$ composites. Benchmark results on the displacement and stress time-histories of FGS cylindrical panels in thermal environments under various pulse loads are presented and discussed in detail. Due to the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state of the art of this problem, and provide pertinent results that are instrumental in the design of FGS structures under time-dependent mechanical loadings.

• Journal of Magnetics
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• v.22 no.2
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• pp.214-219
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• 2017

Magnetic separators that clean the fluid stream from impurities, protect the installations in numerous industries. This paper introduces a graphical user interface (GUI) which proposes an optimized coil separating magnetic particles with a radius from 1 up to 500 µm. High gradient magnetic fields are employed in an arbitrary user defined fluidic channel which is made of a nonmetallic material. The effects of coil parameters are studied and adjusted to design an optimum coil with a minimum Ohmic loss. In addition, to design the coil scheme based on the particle movements, a mathematical particle-tracing model within the fluid channels has been utilized. In comparison to conventional magnetic separators, this model is reconfigurable by the user, produces a weaker magnetic field, allows for continuous purifying and is easy to install, with high separation efficiency. The presented GUI is simple to use, where the coil's manufacturing limitations can be specified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.8
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• pp.654-659
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• 2008

This paper is to suggest a concept design of the permanent magnet type magnetic resonance imaging (MRI) device based on the parameter optimization method. Pulse currents in the gradient coils will introduce the effect of eddy currents in the ferromagnetic material, which will worsen the quality of imaging. In order to equalize the magnetic flux in the MRI device for good imaging, the eddy current effect in the ferromagnetic material must be taken into account. This study attempts to use the design of experiment (DOE) and the response surface method (RSM) for equalizing the magnetic flux of the permanent magnet type MRI device using that the magnetic flux can be calculated directly using a commercial finite element analysis package. As a result, optimal shapes of the pole and the yoke of the PM type MRI device can be obtained. The commercial package, ANSYS, is used for analyzing the magnetic field problem and obtaining the resultant magnetic flux.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.3
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• pp.309-318
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• 2004

This research automatically designed psc-box girder bridges by using an optimum design program and applied the results to the various types of bridges to verify if common facts used in steel bridges or concrete bridges can be applied to PSC bridges. Namely, it investigated appropriate unequal span length division by comparing with bridge of unequal and equal span length division, and verified the influence of the load factors which are changed by time or specification applying the results to various types of bridge. and it applied reinforced concrete bridge and steel bridge's variable girder depth which is slender and effective to save material costs to PSC box girder bridges. Technical solution of optimum design program used SUMT procedure, and Kavlie's extended penalty function to allow infeasible design points in the process. Powell's direct method was used for searching design points and a gradient's approximate method was used to reduce the design time.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.4
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• pp.322-328
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• 2000

Welding means that metal parts are joined by melting (with or without a filler material) or that new material is added to a metal part by melting. Welding of metal parts is an important technology method in manufacturing processes of capstan drum for costal vessels. Thermal stresses due to the non-uniform temperature fields during welding influence both the fabrication and the use of the weldment. In the problem of this thermal effect, particularly it is a well known that analysis for temperature gradient, temperature distribution, and the like become consequence factors to a safety and a strength design. This paper analyzes the temperature distribution of welding part in capstan drum for the inshore and costal vessels using finite element method. At early stage of the cooling after welding processes, the abrupt temperature gradient has been shown in vicinity of the bottom face of welding part. Therefore it calculates the numerical value that can be applied to the optimal design of welding parts in the shapes for capstan drum.