• 한국안전학회지
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• 제32권6호
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• pp.75-80
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• 2017

In this study, seismic performance of various types of valve supports in terms of flexural rigidity are evaluated by FEA using equivalent static load method. Flexural rigidity of the existing two types of valve supports can be effectively improved by simply adding one more bracket on the other side of support. New types of polygonal valve supports with a concept of fully stressed beam theory are suggested and it is verified that the new supports are rigid enough to withstand stronger earthquake which we should be prepared for.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.207-211
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• 2015

In this paper, 2 kinds of models about bike frame are simulated with static structural analysis. A bike frame with diamond type is compared with another model that Down tube is eliminated from original diamond frame. About both types of models, Property of a material and conditions of restriction & load are the same. This study shows reinforcement effects of a partial frame by adding down tube and impacts generated by applying a load at the frame such as weak points & high stress parts as well as expected deformation. The structural result of this study indicates that the equivalent stress or total deformation decreases by 57.1% or 36.4%, respectively. Also stress concentration sites are leg connecting parts, front/rear wheels fixed region and Max deformation is generated from Seat tube. In conclusion, A Down tube is highly efficient as reinforcement than frame without non down tube. Furthermore, The safety rises in case of reducing top tube thickness and increasing a reinforcement at leg connecting parts or concentration regions.

• 대한기계학회논문집A
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• 제34권12호
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• pp.1811-1820
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• 2010

실제 대부분의 공학 문제들은 크고 작은 비선형성을 내포한다. 구조물의 최적설계 과정에서는 다수의 구조물 사이에 발생하는 접촉이나 비선형 물성치를 가지는 재료, 또는 대변형을 고려해야만 한다. 그러나 민감도 계산이 고가이기 때문에 비선형성을 최적화에 고려하는 것은 매우 어렵다. 따라서 비선형 정적 반응 위상최적설계를 위하여 등가하중법을 사용한다. 등가하중이란 비선형 해석에서 유발되는 반응장과 동일한 반응장을 유발하는 선형 정적하중이다. 등가하중법은 치수/형상최적설계를 위하여 연구되어 왔다. 위상최적설계는 치수/형상최적설계에 비하여 설계변수가 많기 때문에 기존의 등가하중법을 그대로 적용할 수 없기 때문에 위상최적설계를 위하여 등가하중법을 확장하고 수정한다. 간단한 예제를 통하여 등가하중법을 이용한 위상최적설계 결과가 수치적으로 도출한 결과와 유사함을 보이고 실제 공학 예제의 위상최적설계를 통하여 기존의 선형 정적 위상최적설계와 결과를 비교한다.

• Structural Engineering and Mechanics
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• 제70권6호
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• pp.737-750
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• 2019

This paper investigates the static and dynamic behaviors of imperfect single walled carbon nanotube (SWCNT) modeled as a beam structure by using energy-equivalent model (EEM), for the first time. Based on EEM Young's modulus and Poisson's ratio for zigzag (n, 0), and armchair (n, n) carbon nanotubes (CNTs) are presented as functions of orientation and force constants. Nonlinear Euler-Bernoulli assumptions are proposed considering mid-plane stretching to exhibit a large deformation and a small strain. To simulate the interaction of CNTs with the surrounding elastic medium, nonlinear elastic foundation with cubic nonlinearity and shearing layer are employed. The equation governed the motion of curved CNTs is a nonlinear integropartial-differential equation. It is derived in terms of only the lateral displacement. The nonlinear integro-differential equation that governs the buckling of CNT is numerically solved using the differential integral quadrature method (DIQM) and Newton's method. The linear vibration problem around the static configurations is discretized using DIQM and then is solved as a linear eigenvalue problem. Numerical results are depicted to illustrate the influence of chirality angle and imperfection amplitude on static response, buckling load and dynamic behaviors of armchair and zigzag CNTs. Both, clamped-clamped (C-C) and simply supported (SS-SS) boundary conditions are examined. This model is helpful especially in mechanical design of NEMS manufactured from CNTs.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 C
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• pp.1164-1166
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• 1999

This paper presents Static Synchronous Series Compensator(SSSC) model for power flow study using IPLAN. In the proposed model, SSSC is represented by the equivalent load variation. The equivalent load consists of active power load specified by user and reactive power load which is founded for considering characteristic of SSSC. And this is implemented by IPLAN which is a macro-external program for PSS/E. Using this model, SSSC can be solved in load-flow by just calling the model in PSS/E. The proposed model was applied to a realistic power system for validity test.

• 한국해양공학회지
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• 제17권5호
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• pp.39-47
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• 2003

A study of the structural strength evaluation on the doubler plate, considering various load cases that were subjected to in-plane and out of plane combined load, has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate for various load cases, elasto-plastic large deflection analysis is introduced, including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed, based on the results. In order to compare the doubler structure with the original strength of main plate, without doubler, simple formulas for the evaluation of the equivalent flat plate thickness are derived for each load case, respectively, based on the additional series of analysis of flat plate structure. Using these derived equations, the thickness change of an equivalent flat plate is analyzed according to the variation of various design parameters of doubler platesome design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas are discovered, and these relations are formulated for the future development of simple strength evaluation formula of general doubler plate structure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.694-699
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring,nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are teansformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response no EL. The objective function is defined by minimizing the maximum stress in the spring while is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• 대한기계학회논문집A
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• 제29권3호
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• pp.369-386
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• 2005

Various aspects of structural optimization techniques under transient loads are extensively reviewed. The main themes of the paper are treatment of time dependent constraints, calculation of design sensitivity, and approximation. Each subject is reviewed with the corresponding papers that have been published since 1970s. The treatment of time dependent constraints in both the direct method and the transformation method is discussed. Two ways of calculating design sensitivity of a structure under transient loads are discussed - direct differentiation method and adjoint variable method. The approximation concept mainly focuses on re- sponse surface method in crashworthiness and local approximation with the intermediate variable Especially, as an approximated optimization technique, Equivalent Static Load method which takes advantage of the well-established static response optimization technique is introduced. And as an application area of dynamic response optimization technique, the structural optimization in flexible multibody dynamic systems is re- viewed in the viewpoint of the above three themes

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.129-134
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• 2003

The importance of understanding the response of structural composites to impact and CAI cannot be overstated to develop analytical models for impact damage and CAI strength predictions. This paper presents experimental findings observed from quasi-static lateral load tests, low velocity impact tests, CAI strength and open hole compressive strength tests using 3mm thick composite plates ($[45/-45/0/90]_{3s}$ - IM7/8552). The conclusion is drawn that damage areas for both quasi-static lateral load and impact tests are similar and the curves of several drop weight impacts with varying energy levels (between 5.4 J and 18.7 J) fallow the static curve well. In addition, at a given energy the peak force is in good agreement between the static and impact cases. From the CAI strength and open hole compressive strength tests, it is identified that the failure behaviour of the specimens was very similar to that observed in laminated plates with open holes under compression loading. The residual strengths are in good agreement with the measured open hole compressive strengths, considering the impact damage site as an equivalent hole. The experimental findings suggest that simple analytical models for the prediction of impact damage area and CAI strength can be developed on the basis of the failure mechanism observed from the experimental tests.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.999-1004
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• 2004

A numerical method and algorithms is proposed to perform optimization of non-linear response structures. An analytical and numerical method based finite element method is also proposed for the transformation of non-linear response into linear response. Loads transformed from this method are defined as the equivalent linear loads. With the loads and the transformed response, linear static optimization is performed for nonlinear response structure with geometric and/or material non-linearity. The results of the optimization are compared with them of typical non-linear response optimization using finite difference method. The proposed method is very efficient and derives good solution.