• 한국강구조학회 논문집
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• 제15권1호
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• pp.33-40
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• 2003

최근 몇 년 동안 파형강관의 사용이 증가하고 있다. 예전의 연구자들은 강관의 파괴모드를 찌그러짐(crushing)이나 변형(deformation)으로 간주하였다. 그러나 강관의 직경이 커지고 두께가 얇아짐에 따라 상대적으로 작은 변형에서 좌굴이 발생하게 된다. 지중 강관의 좌굴해석에서는 두 가지가 있는데, 하나는 지반을 탄성연속체로 보는 것이고, 또 하나는 강관을 탄성스프링으로 지지한다고 가정하는 Winkler 모델이다. 이 두 가지의 해석방법은 파형을 고려하지 않는 평면해석을 기본으로 하고 있다. 본 논문에서는 좌굴해석 수행시 Winkler 모델을 기본으로 하고, 파형의 효과를 고려하는 3차원해석을 수행하여 좌굴하중에 대한 식을 제안하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 학술대회 논문집 전문대학교육위원
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• pp.183-186
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• 2007

Realistic deformation of computer simulated anatomical structures is computationally intensive. As a result, simple methodologies not based in continuum mechanics have been employed for achieving real time deformation of virtual reality. Since the graphical interpolations and simple spring models commonly used in these simulations are not based on the biomechanical properties of tissue structures, these "quick and dirty"methods typically do not accurately represent the complex deformations and force-feedback interactions that can take place during surgery. Finite Element(FE) analysis is widely regarded as the most appropriate alternative to these methods. However, because of the highly computational nature of the FE method, its direct application to real time force feedback and visualization of tissue deformation has not been practical for most simulations. If the mathematics are optimized through pre-processing to yield only the information essential to the simulation task run-time computation requirements can be drastically reduced. To apply the FEM, We examined a various in verse matrix method and a deformed material model is produced and then the graphic deformation with this model is able to force. As our simulation program is reduced by the real-time calculation and simplification because the purpose of this system is to transact in the real time.

• Smart Structures and Systems
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• 제3권1호
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• pp.23-49
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• 2007

Wavelet transforms are the emerging signal-processing tools for damage identification and time-frequency localization. A small perturbation in a static or dynamic displacement profile could be captured using multi-resolution technique of wavelet analysis. The paper presents the wavelet analysis of damaged linear structural elements using DB4 or BIOR6.8 family of wavelets. Starting with a localized reduction of EI at the mid-span of a simply supported beam, damage modeling is done for a typical steel and reinforced concrete beam element. Rotation and curvature mode shapes are found to be the improved indicators of damage and when these are coupled with wavelet analysis, a clear picture of damage singularity emerges. In the steel beam, the damage is modeled as a rotational spring and for an RC section, moment curvature relationship is used to compute the effective EI. Wavelet analysis is performed for these damage models for displacement, rotation and curvature mode shapes as well as static deformation profiles. It is shown that all the damage indicators like displacement, slope and curvature are magnified under higher modes. A localization scheme with arbitrary location of curvature nodes within a pseudo span is developed for steady state dynamic loads, such that curvature response and damages are maximized and the scheme is numerically tested and proved.

• 한국터널지하공간학회 논문집
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• 제17권3호
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• pp.363-382
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• 2015

본 연구는 수치해석을 통하여 TBM 세그먼트의 분할 수와 인접한 링의 이격각도가 라이닝의 부재력에 어떤 영향을 미치는 살펴보았다. 수치해석은 Midas civil 2012+ 프로그램을 사용하였고, 모델링은 2링빔 스프링 모델을 이용하였다. TBM 세그먼드 부재력은 다양한 요소에 의해 결정된다. 본 논문에서는 세그먼트 분할 수와 분포를 제외한 다른 요소인 이음부 스프링 계수, 지반반력계수를 통제하고 특정한 분할 수와 분할 특성을 통해 case를 선정함으로써 분할 수와 분포와 같은 분할 특성이 부재력에 미치는 영향을 분석하였다. 이로써 TBM 세그먼트 시공 설계시 구조적으로 유리하거나 불리한 이음부 특성을 확인할 수 있다.

• Advances in nano research
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• 제6권3호
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• pp.219-242
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• 2018

In this study, static bending of an edge cracked cantilever nanobeam composed of functionally graded material (FGM) subjected to transversal point load at the free end of the beam is investigated based on modified couple stress theory. Material properties of the beam change in the height direction according to exponential distributions. The cracked nanobeam is modelled using a proper modification of the classical cracked-beam theory consisting of two sub-nanobeams connected through a massless elastic rotational spring. The inclusion of an additional material parameter enables the new beam model to capture the size effect. The new non-classical beam model reduces to the classical beam model when the length scale parameter is set to zero. The considered problem is investigated within the Euler-Bernoulli beam theory by using finite element method. In order to establish the accuracy of the present formulation and results, the deflections are obtained, and compared with the published results available in the literature. Good agreement is observed. In the numerical study, the static deflections of the edge cracked FGM nanobeams are calculated and discussed for different crack positions, different lengths of the beam, different length scale parameter, different crack depths, and different material distributions. Also, the difference between the classical beam theory and modified couple stress theory is investigated for static bending of edge cracked FGM nanobeams. It is believed that the tabulated results will be a reference with which other researchers can compare their results.

• 한국자동차공학회논문집
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• 제16권4호
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• pp.97-102
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• 2008

The vibration of a vehicle, which is caused by and transmitted from the engine, has significant effect on the ride comfort and the dynamic characteristics of the engine mount system have direct influence on the vibration and noise of the vehicle. This paper examines the body shake caused by the engine excitation force on engine key on/off of a medium truck by experiment and simulation. The analysis model consists of the engine, a body including the frame, front and rear suspensions and tires. The force element between the body and the suspension is modeled as a combination of a suspension spring and a damper. The engine shake obtained from the experiment was compared with the result of the computer simulation, and by using the verified computer model, parametric study of the body shake on engine key on/off is performed with changing the stiffness of an engine mount rubber, the engine mount angle, and the position of engine mounts.

• 한국강구조학회 논문집
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• 제15권4호통권65호
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• pp.435-445
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• 2003

인장구조물에서의 인장재는 가장 중요한 부재임에도 불구하고, 현재 인장재에 발생하는 현장에서 효과적으로 측정하는 방법에는 어려운 점이 많다. 기존의 측정방법으로는 일시적 또는 특정부재의 측정은 가능하지만 전체부재의 측정과 장기간 측정은 불가능하다. 이에 인장재의 인장력을 측정하기 위한 방법을 제시하고, 인장력이 작용하였을 때 탄성상태에서 부재가 선형적으로 변형하는 성질을 이용하여 인장재의 인장력을 효과적으로 측정하기 위한 방법을 제시하였다. 또한 측정장치의 개발에 필요한 자료를 제공하고자 유한요소해석을 수행하였고, 시험체를 제작하여 실험을 실시하여 해석의 결과를 검증하였다.

• 제어로봇시스템학회논문지
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• 제14권7호
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• pp.663-671
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• 2008

This paper presents a real-time haptic rendering method for multi-contact interaction with virtual environments. Haptic systems often employ physics-based deformation models such as finite-element models and mass-spring models which demand heavy computational overhead. The haptic system can be designed to have two sampling times, T and JT, for the haptic loop and the graphic loop, respectively. A multi-rate output-estimation with an exponential forgetting factor is proposed to implement real-time haptic rendering for the haptic systems with two sampling rates. The computational burden of the output-estimation increases rapidly as the number of contact points increases. To reduce the computation of the estimation, the multi-rate output-estimation with reduced parameters is developed in this paper. Performance of the new output-estimation with reduced parameters is compared with the original output-estimation with full parameters and an exponential forgetting factor. Estimated outputs are computed from the estimated input-output model at a high rate, and trace the analytical outputs computed from the deformation model. The performance is demonstrated by simulation with a linear tensor-mass model.

• 전산구조공학
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• 제10권3호
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• pp.125-131
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• 1997

대부분의 동적계는 기진력 및 계 인자들에 있어서 다양한 불확정 특성을 갖고 있다. 본 연구에서는 기진력의 불확정성과 계 인자들의 불확정성을 모두 갖는 선형 동적계에 대한 응답해석 과정을 제안하였다. 확률특성을 갖는 계 인자와 응답은 섭동법에 의해 모델링되었으며, 응답해석은 불규칙 진동 이론에 의하여 정식화 되었다. 또한 제안된 응답 모델에 의해 계산되기 어려운 응답의 평균에 대한 해석은 확률유한요소법을 사용하였다. 적용 예로서 정상 백색잡음 기진력을 받으며 불확정 질량과 스프링 상수를 갖는 1자유도계 문제에 대하여 과도응답을 계산하고, 그 결과를 수치 시뮬레이션 결과와 비교하여 그 타당성을 검토하였다.

• 소성∙가공
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• 제23권8호
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• pp.482-488
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• 2014

Flexible forming technology has advantages in sheet metal forming, because it can be implemented to produce various shaped molds using a single apparatus. Due to this advantage, it is possible to apply it to the manufacture of an aircraft winglet mold. Presently, most aircraft winglets are manufactured from composite materials. Therefore, the mold for the curing process is an essential element in the fabrication of such composite materials. Compared to conventional mold forming, flexible forming has some advantages such as reduced manufacturing cost and uniformity of mold thickness. If the thickness of the mold is consistent, then the heat transfer will occur uniformly during the curing process leading to improved formability of the composite material. In the current study, numerical simulations were performed to investigate the possibility of flexible forming for manufacturing of the winglet mold. In order to match the size of the actual product, the shape of objective surface was divided to fit the dimensions of the apparatus. The results from the numerical simulations are compared with the objective surface to verify the accuracy. In conclusion, the current study confirms the feasibility and the potential to manufacture winglet molds by flexible forming.