• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.71-71
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• 2017

농용트랙터의 운전자는 작업, 주행으로 인한 유해한 저주파 진동에 장시간 노출된다. 이에 따라 운전자에게 전달되는 노면 진동을 감소시켜주기 위한 전방차축 현가장치의 역할이 커지고 있다. 트랙터의 전방차축 현가장치는 주로 유압식으로 설계되어 있으며 이를 구성하는 유압요소 선정이 현가장치의 성능에 중요한 영향을 미친다. 하지만, 실제와 유사한 조건에서 트랙터 차체 무게만큼 큰 부하를 제공하여 유압회로의 성능을 실험하는 것은 비용과 시간 측면에서 비효율적이다. 본 연구에서는 이를 대체하기 위하여 개별 유압요소의 성능을 테스트 할 수 있는 현가장치 유압회로 요인 시험기를 설계제작 하였다. 이를 이용하여 개별 부품의 성능곡선을 센서를 이용 측정하였고 얻은 특성값을, 구성한 유압 시뮬레이션 모델에 반영하여 실제조건의 유압특성을 얻을 수 있는 유효한 시뮬레이션 모델 개발에 활용하였다. 또한, 실험실 환경에서 유압식 현가장치를 간소화 시킨 형태로 유압회로의 성능을 예비시험해 볼 수 있도록 다양한 센서를 장착 데이터를 취득할 수 있도록 하였다. 개발한 요인 시험기는 하부에 설치된 가진 실린더를 이용하여 상부에 설치된 현가장치 실린더의 스트로크 변위와 속도에 따른 힘을 측정할 수 있도록 구성하였다. 이를 위해 현가장치 실린더의 헤드부와 로드부에 각각 압력센서를 설치하였으며 헤드부, 로드부의 압력 차이와 로드셀을 이용해 측정한 가진 실린더의 힘의 관계를 확인하였다. 상부의 현가 실린더 장치는 복동 형태로 제작되어 헤드부, 로드부 양쪽 방향으로 유량이 흐를 수 있도록 설계되었다. 이를 이용해 헤드부와 로드부 사이에 어큐뮬레이터, 가변 오리피스, 릴리프 밸브 등으로 유압회로를 구성하였으며 어큐뮬레이터 용량에 따른 힘의 변화, 가변 오리피스의 개도량에 따라서 전달되는 힘의 크기 등을 측정하였다. 하부의 가진 실린더는 사인파, 삼각파, 계단 입력, DC 레벨 등의 신호를 발생시킬 수 있도록 제작되었다. 신호의 주파수는 0~4Hz, 범위에서 사용자가 조절할 수 있도록 설정되었으며 계단응답 성능 측정 시험을 평가한 결과 정상상태오차는 0.470mm~0.536mm, 입상시간은 0.194초~0.202초, 정착시간은 0.230초~0.421초로 나타났다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.165-171
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• 2009

This research developed two semi-active MR dampers whose gaps in the orifice area were different from each other, and evaluated their damping performance by loading tests. The Damping performance of MR dampers characteristically depends on various factors like their material and mechanical ones, but most importantly on the size of gap in the orifice area. For this research, we designed the orifice gaps of two dampers as each 1.0mm and 2.0mm, both with the 80mm outer diameter of the orifice. We also designed two loading test sets with different input currents, and acquired different control ability from them. The acquired test results were analyzed and evaluated with their maximum and minimum damping force and also their dynamic range from the force-displacement hysteresis loops and the force-input current relationship curve. This research clearly proved how the damping performance of control devices depends on the gap effect, and also presented a possibility that the two dampers developed in this research could be used for the smart control of construction structures by effectively adapting the input current and the number of coil turns.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.172-180
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• 2009

Normally in order to build a semi-active control system equipped with MR damper, the dynamic modeling of the damper is required to numerically predict its dynamic damping force and also its behavioral characteristics. For the dynamic modeling of the MR damper, this paper attempts to predict and evaluate its dynamic behavior by applying specifically both a power model and a Bingham model. Dynamic loading tests were performed on the squeeze type of damper specially designed for this research, and force-displacement hysteresis loops confirmed the effectiveness of the damper as a semi-active control device. In the meantime, in order to evaluate the effectiveness of each model applied, the model parameter for each model was identified. On the basis of the parameter, we derived the error ratio of the force-velocity relationship curve and the dynamic damping force, which was contrasted and compared with the experimental results of the squeeze type of damper. Finally, the squeeze type of MR damper developed in this research was proved to be valid as a semi-active control device, and also the evaluation of the two dynamic models showed they were working fine so that they were likely to be easily utilized to numerically predict the dynamic characteristics of any dampers with MR fluid as well as the squeeze type of MR damper.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.61-69
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• 2013

This research is aimed to evaluate characteristics and dynamic modeling of MR damper for semi-active vibration control. A MR damper of semi-active type was designed and made for the purpose of controlling the vibration of a real-size model structure. Usually a semi-active control system equipped with a MR damper requires a dynamic model which expresses numerical data about the damping capacity and dynamic characteristics generated by a MR damper. To fulfil the requirement, a Power model and a Bingham model were particularly employed among many dynamic models of MR damper. Those models being contrasted with other ones, a dynamic test was carried out on the developed MR damper. In the test, excitation frequencies were conditioned to be 0.15 Hz, 1.0 Hz, and 2.0 Hz, and three different currents were adopted for each frequency. From these test results, it was found that displacement affected control capacity of the MR damper. The test results led to the identification of model variables for each dynamic model, on the basis of which a force-speed relation curve and expected damping force were derived and contrasted to those of the developed MR damper. Therefore, it was proven that the MR damper designed and made in this research was effective as a semi-active controller, and also that displacement of 2mm at minimum was found to be secured for vibration control, through the test using various displacements.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.119-124
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• 2008

Space structure is a appropriate shape that resists external force only with in-plane force by reducing the influence of bending moment, and it maximizes the effectiveness of structure system. The space structure should be analized by nonlinear analysis regardless static and dynamic analysis because it accompanies large deflection for member. To analyze the structure of the space structure exactly generally geometrically nonlinear and material nonlinear, complex nonlinear analysis are considered. To settle the weakness that geometric nonlinear problem does not consider nonlinear as per trait and position of the structure material and that the nonlinear matter of structure material also does not consider nonlinear as per geometric form. Therefore, In this paper, analysis is considered geometric nonlinear and material nonlinear simultaneous conditioning, and traced load-deflection curve by using ABAQUS which is the general purpose of the finite element program.

• Journal of Korean Association for Spatial Structures
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• v.8 no.1
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• pp.41-48
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• 2008

Spatial structure is an appropriate shape that resists external force only with in-plane forte by reducing the influence of bending moment, and it maximizes the effectiveness of structure system. the spatial structure should be analyzed by nonlinear analysis regardless static and dynamic analysis because it accompanys large deflection for member. To analyze the spatial structure geometrical and material nonlinearity should be considered in the analysis. In this paper, a geometrically nonlinear finite element model for plane truss structures is developed, and material nonlinearity is also included in the analysis. Arc-length method is used to solve the nonlinear finite element model. It is found that the present analysis predicts accurate nonlinear behavior of plane truss.

• Composites Research
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• v.36 no.5
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• pp.377-382
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• 2023

To enhance the performance of graphene-based devices, it is of great importance to better understand the interfacial interaction of graphene with its underlying substrates. In this study, the adhesion energy of monolayer graphene placed on dielectric substrates was characterized using mode I fracture tests. Large-area monolayer graphene was synthesized on copper foil using chemical vapor deposition (CVD) with methane and hydrogen. The synthesized graphene was placed on target dielectric substrates using polymer-assisted wet transfer technique. The monolayer graphene placed on a substrate was mechanically delaminated from the dielectric substrate by mode I fracture tests using double cantilever beam configuration. The obtained force-displacement curves were analyzed to estimate the adhesion energies, showing 1.13 ± 0.12 J/m² for silicon dioxide and 2.90 ± 0.08 J/m² for silicon nitride. This work provides the quantitative measurement of the interfacial interactions of CVD-grown graphene with dielectric substrates.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.213-220
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• 2015

CFT column has a lot of structural advantages due to the composite behavior between in-filled concrete and steel tube. This paper deals with the development of an effective numerical model which can consider the bond-slip behavior between both components of concrete matrix and steel tube without taking double nodes. Since the applied axial load to in-filled concrete matrix is delivered to steel tube by the confinement effect and the friction, the governing equation related to the slip behavior can be constructed on the basis of the force equilibrium and the compatability conditions. In advance, the force and displacement relations between adjacent two nodes make it possible to express the slip behavior with the concrete nodes only. This model results in significant savings in the numerical modeling of CFT columns to take into account the effect of bond-slip. Finally, correlation studies between numerical results and experimental data are conducted to verifying the efficiency of the introduced numerical model.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.2
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• pp.37-46
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• 2009

In this study, the seismic performance of the Buckling Restrained Knee Bracing (BRKB) system was evaluated through a pin-connected 1-bay 1-story frame. The BRKB system using a bolted channel section developed was composed of a steel plate as a load-resisting core member and two channel sections as a restrainment of the local and global buckling of the core plate. The main purpose of the BRKB system is to be used as an effective tool to re-strengthen/rehabilitate old low- and mid-rise RC frame buildings, which do not have enough seismic resistance to earthquake loadings. The main variables for the test specimens were the size of the core plates, stiffeners and the use of guide plates. The test results showed that the size of the core plate, which was the main element for the load-resisting member, was the most important parameter to achieve ductile behavior under tension as well as compression, until the maximum displacement exceed twice the design drift limit given by the AISC Seismic Provisions.