• Coupled systems mechanics
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• 제12권1호
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• pp.21-40
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• 2023

In thisstudy, the vibration problem ofthermo elastic carbon nanotubes conveying pulsating viscous nano fluid subjected to a longitudinal magnetic field is investigated via Euler-Bernoulli beam model. The controlling partial differential equation of motion is arrived by adopting Eringen's non local theory. The instability domain and pulsation frequency of the CNT is obtained through the Galerkin's method. The numerical evaluation of thisstudy is devised by Haar wavelet method (HWM). Then, the proposed model is validated by analyzing the critical buckling load computed in presentstudy with the literature. Finally, the numerical calculation ofsystem parameters are shown as dispersion graphs and tables over non local parameter, magnetic flux, temperature difference, Knudsen number and viscous parameter.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1690-1695
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• 2007

Lightweight metallic truss structures with open, periodic cell are currently being investigated because of their multi-functionality such as thermal management and load bearing. The Kagome truss PCM has been proved that it has higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. The subject of this paper is an examination of the failure mechanism of Wire woven Bulk Kagome(WBK). To address this issue, the out-of-plane compressive responses of the WBK has been measured and compared with theoretical and finite element (FE) predictions. For the experiment, 2 multi-layered WBK are fabricated and 3 specimens are prepared. For the theoretical analysis, the brazed joints of each wire in WBK are modeled as the pin-joint. Then, the peak stress of compressive behavior and elastic modulus are calculated based on the equilibrium equation and energy method. The mechanical structure with five by five cells on the plane are constructed is modeled using the commercial code, PATRAN 2005. and the analysis is achieved by the commercial FE code ABAQUS version 6.5 under the incremental theory of plasticity.

• Computers and Concrete
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• 제5권4호
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• pp.279-293
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• 2008

In the present paper a 3D thermo-hygro-mechanical model for concrete is used to study explosive spalling of concrete cover at high temperature. For a given boundary conditions the distribution of moisture, pore pressure, temperature, stresses and strains are calculated by employing a three-dimensional transient finite element analysis. The used thermo-hygro-mechanical model accounts for the interaction between hygral and thermal properties of concrete. Moreover, these properties are coupled with the mechanical properties of concrete, i.e., it is assumed that the mechanical properties (damage) have an effect on distribution of moisture (pore pressure) and temperature. Stresses in concrete are calculated by employing temperature dependent microplane model. To study explosive spalling of concrete cover, a 3D finite element analysis of a concrete slab, which was locally exposed to high temperature, is performed. It is shown that relatively high pore pressure in concrete can cause explosive spalling. The numerical results indicate that the governing parameter that controls spalling is permeability of concrete. It is also shown that possible buckling of a concrete layer in the spalling zone increases the risk for explosive spalling.

• Journal of Welding and Joining
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• 제17권1호
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• pp.97-103
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• 1999

Ships, structures on the ocean, bridges, and other structures tend to be large by the development of industry. These ultra thick plate were welded with large heat input, which causes welding stresses, deformation and buckling, so it has to be considered the weld design, safety, reliability. The welded residual stresses were produced and redistributed due to the effect of large heat input. The mechanical phenomenon has not been surely identified yet. In spite of the lack of the study on the box column, there are various types of steel frame such as I type, H type, + type and $\bigcirc$ type, used in high story building. In this study, we performed computer simulation with two dimensional heat conduction and plane deformation thermal elasto-plastic finite element computer program as changing the plate thickness to 100mm, 150mm and groove angle to $60^{\circ}C$, $45^{\circ}C$, $30^{\circ}C$ of corner joint in box column. And then, to identify mechanical phenomenon such as the phenomenon of thermal distribution, welding residual stresses and deformation and to decide optimum groove angle and welding condition. The main conclusion can be summarized as follows: 1) Since the groove angle has became cooling down rapidly due to its smaller value, the temperature slope was steeped somewhat. 2) The tensile stress within the welding direction stresses was somewhat decreased at the weld metal and HAZ, increasing of the groove angle. 3) The local stress concentration of the groove angle $60^{\circ}C$ was appeared smaller than groove angle $30^{\circ}$.

• Nuclear Engineering and Technology
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• 제13권4호
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• pp.264-276
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• 1981

TRIGA Mark-III 원자로의 핵특성을 실제운전상태와 유사하게 모사할 수 있는 해석절차를 개발하였다. 계산에 사용한 전산코드는 다군중성자확산 연소계산코드인 CITATION이고 채택한 중성자에너지군의 수는 TRIGA형 원자로에서 일반적으로 사용하는 7군(고속영역 3, 열영역 4)이다. 직접적인 3차원 계산이 현실적으로 불가능하므로 평면 2차원계산과 원통형 2차원 계산으로 3차원 효과를 기하였다. 연구로와 같이 노심이 작은 원자로에 대하여는 중성자평형에서 buckling에 의한 효과가 매우 크기 때문에 이를 정확하게 나타내는 방법의 개발에 중점을 두었다. 본 연구에서는 에너지군 또는 영역에 무관한 buckling을 중성자 수송이론으로 산출하는 전형적인 방법을 사용하지 않고 중성자 확산이론으로서 에너지군별, 영역별 buckling을 산출하였으며, 이를 이용하여 수행한 노심계산의 결과는 만족스러웠다. 계산시 노심은 원자로수조의 중앙부에 있는 것으로 하고 제어봉은 완전히 인출되었으며 동위원생산용 조사시료는 없는 것으로 가정하였다. 계산결과로서 연소에 따른 초과반응도가의 변화, 운전이력에 따른 Xe-135 독작용의 변화, 회전조사시료대의 반응도가를 산출하고 이를 실제 운전자료와 비교하였다. 또한 중성자속 및 출력분포, 노심 각 조사시설에서의 중성자 스펙트럼등에 대한 계산결과도 제시하였다.

• 한국강구조학회 논문집
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• 제28권1호
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• pp.23-34
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• 2016

콘크리트 충전강관 기둥은 강관의 구속효과에 의해 콘크리트의 압축내력 상승과, 콘크리트에 의한 강관의 국부좌굴 보강효과에 의해 부재내력이 상승하고 뛰어난 변형성능을 발휘한다. 하지만, 기둥단면이 커질 경우 합성효과를 발휘하기 위하여 스터드 볼트나 후 시공 앵커 볼트를 사용해야 하는 시공상의 문제점이 발생된다. 이를 극복함과 동시에 합성효과를 증대시키기 위한 방안으로 내부에 리브가 설치된 용접조립 기둥이 소개되었다. 내부 리브는 콘크리트와 맞물려 있어 리브의 변형은 콘크리트의 균열을 촉진시키는 역할을 동반하게 된다. 이러한 잠재적인 문제에 대한 해결책은 강관 리브의 변형에 저항할 수 있도록 콘크리트 인성을 증가시킬 수 있는 방안이 필요하다. 언급된 두 가지의 문제점이 효과적으로 해결될 경우 용접조립 각형강관 기둥은 내화성능 확보가 가능하다고 판단된다. 본 연구에서는 해결방안으로 내부 콘크리트를 강섬유와 혼입하여 기둥 자체의 연성과 인성을 증대시키는 것에 중점을 맞추고 있다. 내화성능 평가를 위한 시험체는 총 8개 로 하중비에 따른 재하가열 실험을 실시하고 화재 전후 거동과 열 변형 능력을 주요변수별로 분석하였다. 실험결과와 선행연구 비교를 통해 열 전달과 열응력 해석 모델의 신뢰성을 확보하였으며, 강섬유 혼입율에 따른 변수해석을 수행하였다.

• Structural Engineering and Mechanics
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• 제67권2호
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• pp.207-217
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• 2018

In past years, numerous problems have vexed engineers with regard to buckling, corrosion, bending, and overloading in damaged steel structures. This article sets out to investigate the possible effects of carbon fiber reinforced polymer (CFRP) and steel plates for retrofitting deficient steel square hollow section (SHS) columns. The effects of axial loading, stiffness, axial displacement, the position and shape of deficient region on the length of steel SHS columns, and slenderness ratio are examined through a detailed parametric study. A total of 14 specimens was tested for failure under axial compression in a laboratory and simulated using finite element (FE) analysis based on a numerical approach. The results indicate that the application of CFRP sheets and steel plates also caused a reduction in stress in the damaged region and prevented or retarded local deformation around the deficiency. The findings showed that a deficiency leads to reduced load-carrying capacity of steel SHS columns and the retrofitting method is responsible for the increase in the load-bearing capacity of the steel columns. Finally, this research showed that the CFRP performed better than steel plates in compensating the axial force caused by the cross-section reduction due to the problems associated with the use of steel plates, such as in welding, increased weight, thermal stress around the welding location, and the possibility of creating another deficiency by welding.