• Title, Summary, Keyword: 구조동역학

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Coupled Flexible Multi-Body Dynamics and Controller Analysis of Machine Tool (공작기계의 유연 다물체 동역학 및 제어기 연계해석)

  • Kim, Dong-Man;Kim, Dong-Hyun;Park, Kang-Kyun;Choi, Hyun-Chul
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.19 no.3
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    • pp.307-312
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    • 2010
  • In this study, advanced computational technique for mechatronic analysis has been developed for the efficient design and test of typical machine tool models. Flexible multi-body dynamic (FMBD) analysis method combined with motion controller including control logics is used to simulate typical operation conditions. The present FMBD machine tool model is composed of flexible column structure, rigid body spindle, vertical motion guide (arm) and screw elements. Driving motor clement with rotating degree-of-freedom is interconnected and governed by the designed Matlab Simulink control logic, and then the position of the spindle is feedback into the control logic. It is practically shown from the results that the investigation of designed machine tools with controller can be effectively conducted and verified.

Characterization of CNT/Polymer Nanocomposites using MD-based Multiscale Method (분자동역학에 기반한 멀티스케일 해석을 이용한 탄소나노튜브/고분자 복합재료의 특성 규명)

  • Yu, Su-Young;Yang, Seung-Hwa;Cho, Maeng-Hyo
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.554-557
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    • 2010
  • 본 논문에서는 동일한 체적분율 가지는 탄소나노튜브 나노복합재의 기계적 특성을 규명하였다. 동일한 chirality를 가지는 서로 다른 크기의 탄소나노튜브를 이용하여 탄소나노튜브의 크기가 복합재의 물성에 미치는 영향을 규명하였다. 복합재료의 분자동역학의 결과 탄소나노튜브의 길이방향의 물성은 크게 증가하나, 전단특성의 물성 강화효과를 나타나지 않았다. 이는 통해 탄소나노튜브와 기지재료 사이의 상호작용력이 복합재료의 전단력을 전달하고, 변형을 유지할 만큼 강하지 않다는 것을 확인하였다. 이와 같은 분자동역학 결과를 바탕으로 멀티스케일 모델을 개발하여 복합재료에서 나타나는 현상을 묘사하였다. 제안된 멀티스케일 모델을 이용하여 다양한 조건의 복합재료에 대한 특성 예측이 가능하다.

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Calculation of the Dynamic Contact Force between a Shipbuilding Block and Wire Ropes of a Goliath Crane for the Optimal Lug Arrangement (최적 러그 배치를 위한 골리앗 크레인의 와이어 로프와 선체 블록간의 동적 접촉력 계산)

  • Ku, Nam-Kug;Roh, Myung-Il;Cha, Ju-Hwan
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.5
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    • pp.375-380
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    • 2012
  • In this study, dynamic load and dynamic contact force between a building block and wire ropes of a goliath crane are calculated during lifting or turn-over of a building block for the design of an optimal lug arrangement system. In addition, a multibody dynamics kernel for implementing the system were developed. In the multibody dynamics kernel, the equations of motion are constructed using recursive formulation. To evaluate the applicability of the developed kernels, the interferences and dynamic contact force between the building block and wire ropes were calculated and then the hull structural analysis for the block was performed using the calculation result.

A Study on Dynamic Matrix Control using Spray and Damper to Once-through Boiler Steam Temperature (스프레이와 댐퍼를 이용한 관류 보일러 스팀 온도의 (2X2) 동역학 행렬 제어에 관한 연구)

  • Kim, Woo-Hun;Moon, Un-Chul
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.1
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    • pp.91-97
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    • 2010
  • In this paper, we present simulation results of Dynamic Matrix Control (DMC) to a Once-through boiler steam temperature. In order to control the steam temperatures, we choose spray and damper as two input variables. Then, the step response model is generated for the two major output variables by step test. After that, on-line optimization is performed using $(2\times2)$ step response model. Proposed controller is applied to the APESS (Doosan company's boiler model simulator) and the simulation results show satisfactory performance of proposed control.

A Study on Vibration Reduction of fan in wall-mounted air conditioner (벽걸이 에어컨의 팬 진동 저감에 관한 연구)

  • Chung, Jin-tai;Kim, Min-sung;Lim, Jong-hyuk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.245-246
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    • 2014
  • 에어컨의 실내기에서 발생하는 소음은 주로 회전하는 팬의 진동에 의하여 발생하게 된다. 이는 구조기인 소음으로 낮은 주파수특성을 갖고, 흡음이나 차음의 소음저감방법으로는 해결하기 어려운 특성을 가지고 있다. 본 연구에서는 벽걸이형 에어컨 원심팬에 발생하는 진동(sway motion)의 원인을 진동실험과 동역학 시뮬레이션을 통하여 규명하였다. 실험적인 측면으로는 시스템분석과 시그널분석을 통하여 원심팬 구성품의 물성치 및 동특성을 확보하였고, 해석적인측면으로는 실험으로 확보된 원심팬의 동특성을 바탕으로 동역학 시뮬레이션 모델을 수립하였다. 실험 및 동역학 시뮬레이션을 바탕으로 원심팬 진동의 원인을 규명하였고, 원심팬 진동의 원인은 원심팬과 모터축사이의 축정렬 불량임을 확인하였다. 이를 해결하고 진동을 저감하기위한 장치를 고안하고 실험을 통하여 진동저감효과를 확인하였다.

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Molecular Dynamics (MD) Study of Proton Exchange Membranes for Fuel Cells (연료전지용 수소이온 교환막의 분자동역학 연구)

  • Park, Chi Hoon;Nam, Sang Yong;Hong, Young Taik
    • Membrane Journal
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    • v.26 no.5
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    • pp.329-336
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    • 2016
  • Proton exchange membrane (PEM) is one of the key components of membrane-electrode assembly (MEA), which plays important role in fuel cell performance together with catalysts. It is widely accepted that water channel morphology inside PEMs as a proton pathway significantly affects the PEM performance. Molecular dynamics (MD) simulations are a very useful tool to understand molecular and atomic structures of materials, so that many related researches are currently being studied. In this paper, we summarize the current research trend in MD simulations, present which properties can be characterized, and finally introduce the usefulness of MD simulations to the researchers for proton exchange membranes.

Multi-scale Analysis of Thin film Considering Surface Effects (표면효과를 고려한 박막구조의 멀티스케일 해석)

  • Cho, Maeng-Hyo;Choi, Jin-Bok;Jung, Kwang-Sub
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.3
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    • pp.287-292
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    • 2007
  • In general, the response of bulk material is independent of its size when it comes to considering classical elasticity theory. Because the surface to bulk ratio of the large solids is very small, the influence of surface can be negligible. But the surface effect plays important role as the surface to bulk ratio becomes larger, that is, the contribution of the surface effect must be considered in nano-size elements such as thin film or beam structure. Molecular dynamics computation has been a conventional way to analyze these ultra-thin structures but this method is limited to simulate on the order of $10^6{\sim}10^9$ atoms for a few nanoseconds, and besides, very time consuming. Analysis of structures in submicro to micro range(thin-film, wire etc.) is difficult with classical molecular dynamics due to the restriction of computing resources and time. Therefore, in this paper, the continuum-based method is considered to simulate the overall physical and mechanical properties of the structures in nano-scale, especially, for the thin-film.

Analysis on Thermomechanical Response to Tensile Deformation of GaN Nanowires (GaN 나노와이어의 인장 변형에 의한 열기계적 거동 해석)

  • Jung, Kwangsub;Zhou, Min;Cho, Maenghyo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.4
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    • pp.301-305
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    • 2012
  • In this work the mechanical behaviors of GaN nanowires are analyzed during tension, compression, and unloading deformations. The thermal conductivity of the nanowires at each deformed state is evaluated using an equilibrium Green-Kubo approach. Under tensile loading, the [0001]-oriented nanowires with hexagonal cross-sections undergo a phase transformation from wurtzite to a tetragonal structure. The phase transformation is not observed under compressive loading. The thermal conductivity decreases on going from compressive strains to tensile strains. The strain dependence of the thermal conductivity results from the relaxation time of phonon. A reverse transformation from the tetragonal structure to the wurtzite structure is observed during unloading. The thermal conductivities in the intermediate states are lower than the conductivity in the wurtzite structure at same strain. Such differences in the thermal conductivity between different atomic structures are mainly due to changes in the group velocity of phonon.