• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.332-337
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• 2009

Recently, boss and rib test based on backward extrusion process was proposed to quantitative evaluate the interfacial friction condition in bulk forming process. In this test, the tube-shaped punch with hole pressurizes the workpiece so that the boss and rib are formed along the hole and outer surface of the punch. It was experimentally and numerically revealed that the height of boss is higher than that of the rib under the severe friction condition. This work is focused on the effect of the punch design and friction condition on deformation pattern in boss and rib test. From the boss and rib test simulations, it was found that there is slight variation in both the heights of boss and rib according to the length of punch land, nose radius, and face angle. However the hole diameter of the punch and the clearance between the punch and die have a significant influence on the heights of the boss and rib. In addition, the effect of flow stress was also investigated on the deformation patterns through FE simulations.

• Geomechanics and Engineering
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• 제22권6호
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• pp.509-518
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• 2020

Multi-layered primary linings have been proved to be highly effective for tunneling in severe squeezing grounds. But there still has not existed well-established design method for it. Basically, there are two main critical problems in this method, including determinations of allowable deformation and distribution of support stiffness. In order to address such problems, an attempt to investigate the mechanical response of a circular tunnel with double primary linings is performed in this paper. Analytical solutions in closed form for stresses and displacements around tunnels are derived. In addition, the effectiveness and reliability of theoretical formulas provided are well validated by using the numerical method. Finally, based on the analytical solutions, a parametric investigation on the effects of allowable deformation and distribution of support stiffness on tunnel performance is conducted. Results show that the rock pressure and displacement are significantly affected by these two design parameters. It can be found that rock pressure decreases as either allowable deformation increases or stiffness of the first primary lining decreases, but rock displacement shows an opposite trend. This paper can provide a useful guidance for the design of multi-layered primary linings.

• 한국해양공학회지
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• 제27권2호
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• pp.27-32
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• 2013

A valve is a marine structure that is subjected to multiple seawater loads. Therefore, it is necessary to define the kind of loads applied to it to confirm whether the structure has sufficient strength. In this research, we aimed to find the optimal solution for the stress and deformation of valves under various loads. We first selected design variables and implement a finite element analysis according to changes in the thickness of each component of a valve based on a central composite design. Next we developed a regression model of the response surface. Using this model, we calculated the optimal objective value based on NSGA-II. Finally, to confirm the correspondence between the optimal objective value and the real FEM value, we compared the optimal result and structural analysis result to verify the performance of NSGA-II.

• 대한기계학회논문집A
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• 제31권10호
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• pp.999-1008
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• 2007

The spacer grid set is a component in the nuclear fuel assembly. The set supports the fuel rods safely. Therefore, the spacer grid set should have sufficient strength for the external impact forces such as earthquake. The fretting wear occurs between the spring of the fuel rod and the spacer grid due to flow-induced vibration. Conceptual design of the spacer grid set is performed based on the Independence Axiom of axiomatic design. Two functional requirements are defined for the impact load and the fretting wear, and corresponding design parameters are selected. The overall flow of design is defined according to the application of axiomatic design. Design for the impact load is carried out by using nonlinear dynamic analysis to determine the length of the dimple. Topology optimization is carried out to determine a new configuration of the spring. The fretting wear is reduced by shape optimization using the homology theory. The deformation of a structure is called homologous if a given geometrical relationship holds before, during, and after the deformation. In the design to reduce the fretting wear, the deformed shape of the spring should be the same as that of the fuel rod. This condition is transformed to a function and considered as a constraint in the shape optimization process. The fretting wear is expected to be reduced due to the homology constraint. The objective function is minimizing the maximum stress to allow a slight plastic deformation. Shape optimization results are confirmed through nonlinear static analysis.

• Earthquakes and Structures
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• 제11권6호
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• pp.967-982
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• 2016

Current codes design the buildings based on life safety criteria. In a performance-based design (PBD) approach, decisions are made based on demands, such as target displacement and performance of structure in use. This type of design prevents loss of life but does not limit damages or maintain functionality. As a newly developed method, resilience-based design (RBD) aims to maintain functionality of buildings and provide liveable conditions after strong ground movement. In this paper, the seismic performance of plain and strengthened RC frames (an eight-story and two low-rise) is evaluated. In order to evaluate earthquake performance of the frames, the performance points of the frames are calculated by the capacity spectrum method (CSM) of ATC-40. This method estimates earthquake-induced deformation of an inelastic system using a reduced response spectrum. Finally, the seismic performances of the frames are evaluated and the results are compared with a resilience-based design criterion.

• Structural Engineering and Mechanics
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• 제27권5호
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• pp.541-554
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• 2007

A simplified yet effective design procedure for viscous dampers was presented based on improved capacity spectrum method in the context of performance-based seismic design. The amount of added viscous damping required to meet a given performance objective was evaluated from the difference between the total demand for effective damping and inherent damping plus equivalent damping resulting from hysteretic deformation of system. Application of the method is illustrated by means of two examples, using Chinese design response spectrum and mean response spectrum. Nonlinear dynamic analysis results indicate that the maximum displacements of structures installed with supplemental dampers designed in accordance with the proposed method agree well with the given target displacements. The advantage of the presented procedure over the conventional iterative design method is also highlighted.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.841-843
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• 2002

A novel and simple method, which can be used to automatically regenerate 3D finite element meshes, is presented in the paper. This technique based on the structural deformation analysis. It is problem independent and can be used to renew the mesh of any kind of 3D shape design system whether the geometric surface is parameterized or not. The mesh deformation degree can be adjusted by choosing suitable subregion and giving proper parameters. It is sufficient to obtain a smooth contour with proper mesh quality. Application to the optimum design of shielding plate shows the effectiveness of the proposed technique.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.528-533
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• 2004

This paper deals with the issue of door height difference (DHD) which occurs for SBS refrigerator necessarily. In order to identify the cause of DHD, analysis of refrigerator structure and entire process from door manufacturing to usage have been investigated. From diverse experiments, it was found that the flatness of the floor was a main causing factor. In order to decrease the DHD , the effects of 6 design parameters to control of cabinet deformation have been investigated by using DOE(design of experiment) and finite element analysis. Based on the correlation equation, it was possible to estimate the DHD for new refrigerator design.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.179-182
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• 1997

One-step inverse methods based on deformation theory causes some amount of error. The amount of error is generally increased as the deformation path is more complex. As a remedy, a new three dimensional multi-step inverse method is introduced for optimum design of blank shapes and strain distributions from desired final shapes. The approach extends a one-step inverse method to a multi-step inverse method in order to reduce the amount of error. The algorithm developed is applied to square cup drawing to confirm its validity by demonstrating reasonably accurate numerical results.

• 한국산학기술학회논문지
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• 제11권1호
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• pp.43-48
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• 2010

본 논문의 목적은 액체 살포시 사용되는 초미립자 살포기에 대하여 SolidWorks를 이용하여 설계하고 3차원 유한요소해석 코드인 ANSYS를 활용하여 해석하였다. 해석결과로서 응력, 변형률과 전체 변형량을 구하였고 이를 활용하여 초미립자 살포기의 구조를 개선하였으며 이러한 방법은 생산성 향상과 설계기간을 단축할 수 있다.