• Advances in nano research
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• 제7권3호
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• pp.181-190
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• 2019

The thermal buckling temperature values of the graded carbon nanotube reinforced composite shell structure is explored using higher-order mid-plane kinematics and multiscale constituent modeling under two different thermal fields. The critical values of buckling temperature including the effect of in-plane thermal loading are computed numerically by minimizing the final energy expression through a linear isoparametric finite element technique. The governing equation of the multiscale nanocomposite is derived via the variational principle including the geometrical distortion through Green-Lagrange strain. Additionally, the model includes different grading patterns of nanotube through the panel thickness to improve the structural strength. The reliability and accuracy of the developed finite element model are varified by comparison and convergence studies. Finally, the applicability of present developed model was highlight by enlighten several numerical examples for various type shell geometries and design parameters.

• Advances in materials Research
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• 제11권4호
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• pp.331-349
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• 2022

In the present work, we proposed an analytical study on buckling behavior of a sandwich plate with polymeric core integrated with piezo-electro-magnetic layers such as BaTiO3 and CoFe2O4 reinforced by graphene platelets (GPLs). The Halpin-Tsai micromechanics model is used to describe the properties of the polymeric core. The governing equations of equilibrium are obtained from first-order shear deformation theory (FSDT) and the Navier's method is employed to solve the equations. The results show the effect of different parameters such as thickness, length, weight fraction of GPLs, and also effect of electric and magnetic field on critical buckling load. The result of this study can be obtained in the aerospace industry and also in the design of sensors and actuators.

• Steel and Composite Structures
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• 제48권6호
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• pp.709-725
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• 2023

This paper uses a new type of deformation theory to establish the free vibration and static buckling equations of nanoplates resting on two-parameter elastic foundations, in which the flexoelectric effect is taken into account. The proposed approach used in this work is not only simpler than other higher-order shear deformation theories but also does not need any shear correction coefficients to describe exactly the mechanical responses of structures. The reliability of the theory is verified by comparing the numerical results of this work with those of analytical solutions. The results show that the flexoelectric effect significantly changes the natural frequency and the critical buckling load of the nanoplate compared with the case of neglecting this effect, especially when the plate thickness changes and with some different boundary conditions. These are new results that have not been mentioned in any publications but are meaningful in engineering practice.

• Coupled systems mechanics
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• 제13권2호
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• pp.171-186
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• 2024

In the present paper, thermal buckling characteristics of functionally graded rectangular plates made of porous material that are integrated with surface-bonded piezoelectric actuators subjected to the combined action of thermal load and constant applied actuator voltage are investigated by utilizing a Navier solution method. The uniform temperature rise loading is considered. Thermomechanical material properties of FGM plates are assumed to be temperature independent and supposed to vary through thickness direction of the constituents according to power-law distribution (P-FGM) which is modified to approximate the porous material properties with even and uneven distributions of porosities phases. The governing differential equations of stability for the piezoelectric FGM plate are derived based on higher order shear deformation plate theory. Influences of several important parameters on the critical thermal buckling temperature are investigated and discussed in detail.

• 전산구조공학
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• 제7권1호
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• pp.69-81
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• 1994

본 논문은 형상의 비선형성을 고려한 큰 동하중을 받는 낮은 원호아치의 동적해석에 관한 연구이다. 따라서 낮은 원호아치를 대상으로 동적 비선형 해석을 수행하고 임계좌굴하중을 구할 수 있는 컴퓨터 프로그램을 개발하는데 주안점을 둔다. 형상의 비선형성은 Lagrangian 운동좌표를 고려하여 해석하였으며 비선형 동적 운동방정식을 풀기 위하여 유한요소법을 사용하였다. 개발된 프로그램을 사용하여 만재 방사형 등분포하중을 받는 원호아치를 해석하고, 그 결과를 다른 연구결과와 비교하여 검증하였다. 또한 여러가지의 형상의 아치에 대한 좌굴 해석을 실시하여 임계좌굴하중을 구하였으며 기존의 연구와 비교하여 정확성을 확인하였다. 모형해석을 통해서 큰 동하중을 받는 원호아치는 기하학적 비선형 거동을 고려하여 해석되어야 하며 아치가 낮아질수록 좌굴발생 가능성이 높아짐을 알 수 있다.

• Structural Engineering and Mechanics
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• 제57권3호
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• pp.543-567
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• 2016

This study attempts to address the buckling and free vibration characteristics of an isotropic cylindrical panel subjected to non-uniform temperature rise using numerical approach. Finite element analysis has been used in the present study. The approach involves three parts, in the first part non-uniform temperature field is obtained using heat transfer analysis, in the second part, the stress field is computed under the thermal load using static condition and, the last part, the buckling and pre-stressed modal analysis are carried out to compute critical buckling temperature as well as natural frequencies and associated mode shapes. In the present study, the effect of non-uniform temperature field, heat sink temperatures and in-plane boundary constraints are considered. The relation between buckling temperature under uniform and non-uniform temperature fields has been established. Results revealed that decrease (Case (ii)) type temperature variation field influences the fundamental buckling mode shape significantly. Further, it is observed that natural frequencies under free vibration state, decreases as temperature increases. However, the reduction is significantly higher for the lowest natural frequency. It is also found that, with an increase in temperature, nodal and anti-nodal positions of free vibration mode shapes is shifting towards the location where the intensity of the heat source is high and structural stiffness is low.

• Steel and Composite Structures
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• 제8권2호
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• pp.159-178
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• 2008

An analytical procedure is presented for the determination of the buckling load and the buckling temperature of a straight, slender, geometrically perfect, axially loaded, translationally and rotationally restrained steel column exposed to fire. The exact kinematical equations of the column are considered, but the shear strain is neglected. The linearized stability theory is employed in the buckling analysis. Behaviour of steel at the elevated temperature is assumed in accordance with the European standard EC 3. Theoretical findings are applied in the parametric analysis of restrained columns. It is found that the buckling length factor decreases with temperature and depends both on the material model and stiffnesses of rotational and translational restraints. This is in disagreement with the buckling length for intermediate storeys of braced frames proposed by EC 3, where it is assumed to be temperature independent. The present analysis indicates that this is a reasonable approximation only for rather stiff rotational springs.

• Nuclear Engineering and Technology
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• 제33권1호
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• pp.93-101
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• 2001

The spacer grid is one of the main structural components in the fuel assembly, which supports the fuel rods, guides cooling water, and protects the system from an external impact load, such as earthquakes. Therefore, the mechanical and structural properties of the spacer grids must be extensively examined while designing them. In this paper, a numerical method for predicting the buckling strength of spacer grids is presented. Numerical analyses on the buckling behavior of the spacer grids are performed for a various array of sizes of the grids considering that the spacer grid is an assembled structure with thin-walled plates and imposing proper boundary conditions by nonlinear dynamic finite element method using ABAQUS/Explicit. Buckling tests on several numbers of specimens of the spacer grid were also carried out in order to compare the results between the test and the simulation result. The drop test is accomplished by dropping a carriage on the specimen at a pre-determined position. From this test, the specimens are buckled only at the uppermost and the lowermost layer among the multi-cells, which is similar to the local buckling at the weakest point of the grid structure. The simulated results also similarly predicted the local buckling phenomena and were found to give good correspondence with the experimental values for the thin-walled grid structures.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.123-134
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• 2022

The stability of cable-stayed bridges is an important factor considered during design. In recent years, the novel spatial diamond-shaped bridge pylon has shown its advantages in various aspects, including the static response and the stability performance with the development of cable-stayed bridge towards long-span and heavy-load. Based on the energy approach, this paper presents a practical calculation method of the completed state stability of a cable-stayed bridge with two spatial diamond-shaped pylons. In the analysis, the possible transverse buckling of the girder, the top pylon column, and the mid pylon columns are considered simultaneously. The total potential energy of the spatial diamond-shaped pylon cable-stayed bridge is calculated. And based on the principle of stationary potential energy, the transverse buckling coefficients and corresponding buckling modes are obtained. Furthermore, an example is calculated using the design parameters of the Changtai Yangtze River Bridge, a 1176 m cable-stayed bridge under construction in China, to verify the effectiveness and accuracy of the proposed method in practical engineering. The critical loads and the buckling modes derived by the proposed method are in good agreement with the results of the finite element method. Finally, cable-stayed bridges varying pylon and girder stiffness ratios and pylon geometric dimensions are calculated to discuss the applicability and advantages of the proposed method. And a further discussion on the degrees of the polynomial functions when assuming buckling modes are presented.

• 대한토목학회논문집
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• 제26권3A호
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• pp.457-464
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• 2006

화이버로 보강된 복합재료는 비강성과 강도가 높을 뿐만 아니라 경량화를 위한 작업이 가능한 재료로써, 항공, 선박 그리고 토목분야와 같은 많은 산업분야에서 계속적으로 사용이 증대되고 있다. 본 연구는 전단변형을 고려한 타원단면을 갖는 복합적 층 구조물의 좌굴하중 및 모드형상을 분석하였다. 좌굴해석을 수행하기 위해, 면내회전자유도를 갖는 평면응력 요소와 휨 요소를 결합하여 무결점 4절점 쉘요소를 작성하였다. 이때 추가변형률과 대체전단변형률을 도입함으로써 요소의 거동을 개선하였다. 해석모델에 대해 쉘의 기하학적 형상, 종횡비, 화이버 보강각도, 그리고 적층배열에 따른 영향을 고찰하였다. 본 연구에서 제시한 타원단면을 갖는 적층관의 임계좌굴하중과 모드형상은 여러 가지 설계변수에 의한 거동에 대한 정확한 이해로부터 효율적인 설계방향을 제시하고자 하였으며, 추후 적층관의 좌굴해석시 좋은 참고자료로 활용할 수 있으리라 기대된다.