• Steel and Composite Structures
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• 제25권4호
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• pp.415-426
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• 2017

The thermo-mechanical vibration behavior of two dimensional functionally graded (2D-FG) porous nanobeam is reported in this paper. The material properties of the nanobeam are variable along thickness and length of the nanobeam according to the power law function. The nanobeam is modeled within the framework of Timoshenko beam theory. Eringen's nonlocal elasticity theory is used to develop the governing equations. Using the generalized differential quadrature method (GDQM) the governing equations are solved. The effect of porosity, temperature distribution, nonlocal value, L/h, FG power indexes along thickness and length and are investigated using parametric studies.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.275-290
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• 2018

The hygrothermal stresses in sandwich plate with composite faces due to through the thickness gradient temperature and (or) moisture content are investigated. The layer-wise theory is employed for formulation of the problem. The formulation is derived for sandwich plate with general layer stacking, subjected to uniform and non-uniform temperature and moisture content through the thickness of the plate. The governing equations are solved for free edge conditions and 3D stresses are investigated. The out of plane stresses are obtained by equilibrium equations of elasticity and by the constitutive law and the results for especial case are compared with the predictions of a 3D finite element solution in order to study the accuracy of results. The three-dimensional stresses especially the free edge effect on the distribution of the stresses is studied in various sandwich plates and the effect of uniform and non-uniform thermal and hygroscopic loading is investigated.

• Advances in Computational Design
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• 제3권3호
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• pp.303-318
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• 2018

This article presents a semi-analytical solution for an exponentially graded piezoelectric hollow sphere. The sphere interacts with electric displacement, elastic deformations, electric potentials, magneto-thermo-elasticity, and hygrothermal influences. The hollow sphere may be standing under both mechanical and electric potentials. Electro-magneto-elastic behavior of magnetic field vector can be described in the hollow sphere. All material, thermal and magnetic properties of hollow sphere are supposed to be graded in radial direction. A semi-analytical technique is improved to deduce all fields in which different boundary conditions for radial stress and electric potential are presented. Numerical examples for radial displacement, radial and hoop stresses, and electric potential are investigated. The influence of many parameters is studied. It is seen that the gradation of all material, thermal and magnetic properties has particular effectiveness in many applications of modern technology.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.631-635
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• 1996

Stress singularities appear at the interface edge in dissimilar materials also under thermal loading. First, these singularities then an interface meets a free side surface with an arbitrary angle are studied for a two-dimensional problem. The singular properties under thermal loading are made clear and the concrete singular field are obtained. Secondly, the dependence of stress field on elastic constants in axisymmetric dissimilar materials are. discussed. That is, it is shown that three elastic constants mutually independent are necessary, in general, to characterize the stress field of axisymmetric dissimilar materials, although Dunders' parameters defined for two-dimensional dissimilar materials have been often applied correspondingly also to axisymmetric problems.

• 소성∙가공
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• 제27권6호
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• pp.363-369
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• 2018

This study measured the mechanical properties of an ash wood under various temperature and humidity conditions and a finite element model was developed to predict the behavior of the wood. A humidity-controlled chamber was developed and used for measuring the dimensional changes of woods under various humidity conditions. The thermal expansion coefficient and the elastic stiffness constants were measured by using a thermal chamber and the three-point bending test along the three principal axes of the wood. A constitutive model was proposed to describe the moisture content and temperature dependent behavior of wood. The proposed model was validated for the warping test of a wood plate. The warping of the plate was calculated using the finite element method. The calculated amount of warping was in consistence with the measurements.

• Structural Engineering and Mechanics
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• 제85권1호
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• pp.135-145
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• 2023

This study presents the free vibrational responses of bi-directional axially graded cylindrical shell panels using 3D graded finite element approximation under a temperature field. The cylindrical shell panel is graded in two directions and made of metal-ceramic materials. To extract material properties, the Voigt model is combined with a Power-law material distribution. Convergence and validation studies are performed on the developed computational model to ensure its accuracy and effectiveness. Furthermore, a parametric study is performed to evaluate the developed model, which demonstrates that geometrical parameters, imperfect materials (porosity), support conditions, and surface temperature all have a significant impact on the free vibration responses of a bi-directional axially graded cylindrical shell panel in a thermal environment.

• Computers and Concrete
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• 제31권2호
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• pp.139-149
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• 2023

This article investigates the statically analysis regarding the thermal buckling behavior of a nonuniform small-scale nanobeam made of functionally graded material based on classic beam theories along with the nonlocal Eringen elasticity. The material distribution of functionally graded structures is composed of temperature-dependent ceramic and metal phases in axial and thickness directions, called two-dimensional functionally graded (2D-FG). The partial differential (PD) formulations and end conditions are extracted by using to the conservation energy method. The porosity voids are assumed in the nonuniform functionally graded (FG) structure. The thermal loads are in the axial direction of the beam. The extracted nonlocal PD equations are also solved by employing generalized differential quadrature method (GDQM). Last but not least, the information acquired is used to produce miniature sensors, providing a unique perspective on the growth of nanoelectromechanical systems (NEMS).

• Advances in materials Research
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• 제12권4호
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• pp.309-330
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• 2023

The humid thermal vibration characteristics of a nonhomogeneous thermopiezoelectric nonlocal plate of polygonal shape are addressed in the purview of generalized nonlocal thermoelasticity. The plate is initially stressed, and the three-dimensional linear elasticity equations are taken to form motion equations. The problem is solved using the Fourier expansion collocation method along the irregular boundary conditions. The numerical results of physical variables have been discussed for the triangle, square, pentagon, and hexagon shapes of the plates and are given as dispersion curves. The amplitude of non-dimensional frequencies is tabulated for the longitudinal and flexural symmetric modes of the thermopiezoelectric plate via moisture and thermal constants. Also, a comparison of numerical results is made with existing literature, and good agreement is reached.

• Steel and Composite Structures
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• 제18권1호
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• pp.1-28
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• 2015

In this paper, the dynamic response of functionally gradient steel (FGS) composite cylindrical panels in steady-state thermal environments subjected to impulsive loads is investigated for the first time. FGSs composed of graded ferritic and austenitic regions together with bainite and martensite intermediate layers are analyzed. Thermo-mechanical material properties of FGS composites are predicted according to the microhardness profile of FGS composites and approximated with appropriate functions. Based on the three-dimensional theory of thermo-elasticity, the governing equations of motionare derived in spatial and time domains. These equations are solved using the hybrid Fourier series expansion-Galerkin finite element method-Newmark approach for simply supported boundary conditions. The present solution is then applied to the thermo-elastic dynamic analysis of cylindrical panels with three different arrangements of material compositions of FGSs including ${\alpha}{\beta}{\gamma}M{\gamma}$, ${\alpha}{\beta}{\gamma}{\beta}{\alpha}$ and ${\gamma}{\beta}{\alpha}{\beta}{\gamma}$ composites. Benchmark results on the displacement and stress time-histories of FGS cylindrical panels in thermal environments under various pulse loads are presented and discussed in detail. Due to the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state of the art of this problem, and provide pertinent results that are instrumental in the design of FGS structures under time-dependent mechanical loadings.

• 한국강구조학회 논문집
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• 제12권6호
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• pp.759-767
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• 2000

본 연구는 화재발생후에 시간경과에 따른 콘크리트충전 강관기둥의 내력변화를 파악하고 인장강도시험을 통해 내화실험이전과 후의 항복강도, 인장강도, 평균연신율 및 탄성계수 등에 대하여 각 단계별 하중에 따른 변형률을 비교측정하였다. 화재를 입은 강관내의 충전콘크리트의 물성변화(압축강도 및 탄성계수시험)를 파악하기 위하여 화재실험후 강관중심부에서 코아시험체를 채취하여 압축강도를 측정하고 탄성계수의 측정은 응력에 의한 변형률을 측정하였으며, 대상실험체의 화재온도를 추정하기 위하여 시차열분석을 실시하였다. 이러한 실험결과로부터 얻어진 자료를 평가하여, 향후 콘크리트 충전강관의 내화설계 구조규준제정에 필요한 기초자료를 제시하는데 그 목적이 있다.