• Structural Engineering and Mechanics
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• v.57 no.3
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• pp.473-506
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• 2016

The aim of this work is the development of a 2D quadrilateral isoparametric finite element model, based on a layerwise approach, for the bending analysis of sandwich plates. The face sheets and the core are modeled individually using, respectively, the first order shear deformation theory and the third-order plate theory. The displacement continuity condition at the interfaces 'face sheets-core' is satisfied. The assumed natural strains method is introduced to avoid an eventual shear locking phenomenon. The developed element is a four-nodded isoparametric element with fifty two degrees-of-freedom (52 DOF). Each face sheet has only two rotational DOF per node and the core has nine DOF per node: six rotational degrees and three translation components which are common for the all sandwich layers. The performance of the proposed element model is assessed by six examples, considering symmetric/unsymmetric composite sandwich plates with different aspect ratios, loadings and boundary conditions. The numerical results obtained are compared with the analytical solutions and the numerical results obtained by other authors. The results indicate that the proposed element model is promising in terms of the accuracy and the convergence speed for both thin and thick plates.

• Smart Structures and Systems
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• v.10 no.2
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• pp.111-130
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• 2012

Satellites with flexible lightweight solar panels are sensitive to vibration that is caused by internal actuators such as reaction or momentum wheels which are used to control the attitude of the satellite. Any infinitesimal amount of unbalance in the reaction wheels rotors will impose a harmonic excitation which may interact with the solar panels structure. Therefore, quenching the solar panel's vibration is of a practical importance. In the present work, the panels are modeled as laminated composite beam using first-order shear deformation laminated plate theory which accounts for rotational inertia as well as shear deformation effects. The vibration suppression is achieved by bonding patches of piezoelectric material with suitable dimensions at selected locations along the panel. These patches are actuated by driving control voltages. The governing equations for the system are formulated and the dynamic Green's functions are used to present an exact yet simple solution for the problem. A guide lines is proposed for determining the values of the driving voltage in order to suppress the induced vibration.

• Structural Engineering and Mechanics
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• v.31 no.5
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• pp.481-506
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• 2009

The present study is concerned with the stochastic linear free vibration study of laminated composite plate embedded with piezoelectric layers with random material properties. The system equations are derived using higher order shear deformation theory. The lamina material properties of the laminate are modeled as basic random variables for accurate prediction of the system behavior. A $C^0$ finite element is used for spatial descretization of the laminate. First order Taylor series based mean centered perturbation technique in conjunction with finite element method is outlined for the problem. The outlined probabilistic approach is used to obtain typical numerical results, i.e., the mean and standard deviation of natural frequency. Different combinations of simply supported, clamped and free boundary conditions are considered. The effect of side to thickness ratio, aspect ratio, lamination scheme on scattering of natural frequency is studied. The results are compared with those available in literature and an independent Monte Carlo simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.70-80
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• 2001

A cycloid reducer is one of the rotational velocity reduction equipments of machinery. It has advantages of the higher reduction ratio, the higher accuracy, the easier adjustment of transmission ratio and the smaller workspace than other kinds of reducer. A cycloidal plate gear is a main part of the cycloid reducer. Its tooth shape is peculiar because of gearing with the roller gear that has the several rollers on the circular line. And then it can be designed to contact all teeth to rollers. So, the cycloid reducer has the good characteristics in the dynamic properties and the zero-backlash in the contact motion. It can be used in robots, high-precision machines and high capacity machinery. This paper proposes a new approach for the shape design of the cycloidal plate gear and presents a Computer-Aided-Design program developed by the proposed method. The first part of this paper defines the two types of the cycloid reducers and explains their mechanisms. The second part defines the instant velocity centers for each type of the cycloid reducers and calculates the contact angles and the contact points by using te geometric relationships and the kinematical properties of the reducers. The third part generates the full shape of the cycloidal plate gear by the coordinate transformation technique. Finally, this paper presents two examples for the shape design of the cycloidal plate gear in order to prove the theory of the proposed method in this paper and the accuracy of the \"CycloGear Designer\".

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.405-413
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• 2017

In this paper, we study the biaxial buckling analysis of nonlocal MEE(magneto-electro-elastic) nano plates based on the first-order shear deformation theory. The in-plane electric and magnetic fields can be ignored for MEE(magneto-electro-elastic) nano plates. According to magneto-electric boundary condition and Maxwell equation, the variation of magnetic and electric potentials along the thickness direction of the MME plate is determined. In order to reformulate the elastic theory of MEE(magneto-electro-elastic) nano-plate, the nonlocal differential constitutive relations of Eringen is used. Using the variational principle, the governing equations of the nonlocal theory are discussed. The relations between nonlocal and local theories are investigated by computational results. Also, the effects of nonlocal parameters, in-plane load directions, and aspect ratio on structural responses are studied. Computational results show the effects of the electric and magnetic potentials. These computational results can be useful in the design and analysis of advanced structures constructed from MEE(magneto-electro-elastic) materials and may be the benchmark test for the future study.

• International Journal of Advanced Culture Technology
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• v.9 no.1
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• pp.121-128
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• 2021

In this study, we aim to suggest direction for landscape design of residential complex in Korea by studying target areas to understand how landscape urbanism was applied to residential landscape design as it is the majority of landscape design in Korea and by closely examining design elements to be considered for design of residential complex based on landscape urbanism theory. For the purpose of the study, some of public multifamily housing complex were selected as target areas and a survey was first conducted to understand how landscape urbanism was applied to design of these target areas. Then, by analyzing the survey results, we identified which elements were of importance to designing of multifamily housing complexes in Korea and how practical design of landscape urbanism works. From this study, we concluded that landscape urbanism theory is not just about design strategies, but more of comprehensive design methodology covering both operation and management and that such theory can be appropriately applied to design of multi-housing complexes in Korea. We also discovered that in order to apply landscape urbanism in design stage for multi-housing complex, selecting which design strategy/words in the previous study is not what's important, but comprehensive understanding and interpretation of design languages is key.

• Steel and Composite Structures
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• v.31 no.5
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• pp.503-516
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• 2019

This work presents a dynamic investigation of functionally graded (FG) plates resting on elastic foundation using a simple quasi-3D higher shear deformation theory (quasi-3D HSDT) in which the stretching effect is considered. The culmination of this theory is that in addition to taking into account the effect of thickness extension (${\varepsilon}_z{\neq}0$), the kinematic is defined with only 4 unknowns, which is even lower than the first order shear deformation theory (FSDT). The elastic foundation is included in the formulation using the Pasternak mathematical model. The governing equations are deduced through the Hamilton's principle. These equations are then solved via closed-type solutions of the Navier type. The fundamental frequencies are predicted by solving the eigenvalue problem. The degree of accuracy of present solutions can be shown by comparing it to the 3D solution and other closed-form solutions available in the literature.

• Computers and Concrete
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• v.25 no.3
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• pp.225-244
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• 2020

The influence of boundary conditions on the bending and free vibration behavior of functionally graded sandwich plates resting on a two-parameter elastic foundation is examined using an original novel high order shear theory. The Hamilton's principle is used herein to derive the equations of motion. The number of unknowns and governing equations of the present theory is reduced, and hence makes it simple to use. This theory includes indeterminate integral variables and contains only four unknowns in which any shear correction factor not used, with even less than the conventional theory of first shear strain (FSDT). Unlike any other theory, the number of unknown functions involved in displacement field is only four, as against five, six or more in the case of other shear deformation theories. Galerkin's approach is utilized for FGM sandwich plates with six different boundary conditions. The accuracy of the proposed solution is checked by comparing it with other closed form solutions available in the literature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.52-60
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• 2017

This study examined the structural stability of nonlocal magneto-electro-elastic nano plates on elastic foundations using first-order shear deformation theory. Navier's method has been used to solve the buckling loads for all edges simply supported boundary conditions. On the other hand, biaxial buckling analysis of nano-plates has beenrarely studied. According to the Maxwell equation and the magneto-electro boundary condition, the change inthe magnetic and electric potential along the thickness direction of the magneto-electro-elastic nano plate wasdetermined. To reformulate the elasticity theory of the magneto- electro-elastic nano plate, the differential constitutive equation of Eringen was used and the governing equation of the nonlocal elasticity theory was studied using variational theory. The effects of the elastic foundation arebased on Pasternak's assumption. The relationship between nonlocal theory and local theory was analyzed through calculation results. In addition, structural stability problems were investigated according to the electric and magnetic potentials, nonlocal parameters, elastic foundation parameters, and side-to-thickness ratio. The results of the analysis revealedthe effects of the magnetic and electric potential. These calculations can be used to compare future research on new material structures made of magneto-electro-elastic materials.

• Structural Engineering and Mechanics
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• v.16 no.3
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• pp.259-274
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• 2003

In this paper, a novel numerical solution technique, the differential cubature method is employed to study the buckling problems of thick plates with arbitrary quadrilateral planforms and non-uniform boundary constraints based on the first order shear deformation theory. By using this method, the governing differential equations at each discrete point are transformed into sets of linear homogeneous algebraic equations. Boundary conditions are implemented through discrete grid points by constraining displacements, bending moments and rotations of the plate. Detailed formulation and implementation of this method are presented. The buckling parameters are calculated through solving a standard eigenvalue problem by subspace iterative method. Convergence and comparison studies are carried out to verify the reliability and accuracy of the numerical solutions. The applicability, efficiency, and simplicity of the present method are demonstrated through solving several sample plate buckling problems with various mixed boundary constraints. It is shown that the differential cubature method yields comparable numerical solutions with 2.77-times less degrees of freedom than the differential quadrature element method and 2-times less degrees of freedom than the energy method. Due to the lack of published solutions for buckling of thick rectangular plates with mixed edge conditions, the present solutions may serve as benchmark values for further studies in the future.