• Steel and Composite Structures
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• 제52권4호
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• pp.487-499
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• 2024

The primary objective of this study is to analyze the free vibration behavior of a sandwich cylindrical shell with a defective core and wavy carbon nanotube (CNT)-enhanced face sheets, utilizing the three-dimensional theory of elasticity. The intricate equations of motion for the structure are solved semi-analytically using the generalized differential quadrature method. The shell structure consists of a damaged isotropic core and two external face sheets. The distributions of CNTs are either functionally graded (FG) or uniform across the thickness, with their mechanical properties determined through an extended rule of mixture. In this research, the conventional theory regarding the mechanical effectiveness of a matrix embedding finite-length fibers has been enhanced by introducing tube-to-tube random contact. This enhancement explicitly addresses the progressive reduction in the tubes' effective aspect ratio as the filler content increases. The study investigates the influence of a damaged matrix, CNT distribution, volume fraction, aspect ratio, and waviness on the free vibration characteristics of the sandwich cylindrical shell with wavy CNT-reinforced face sheets. Unlike two-dimensional theories such as classical and the first shear deformation plate theories, this inquiry is grounded in the three-dimensional theory of elasticity, which comprehensively accounts for transverse normal deformations.

• 대한기계학회논문집
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• 제13권3호
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• pp.323-329
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• 1989

본 연구에서는 판이론으로서는 해석이 불가능한 집중하중작용점에서 응력을 해석할 목적으로 3차원탄성이론과 변링포텐셜(POTENTIAL) 이론을 이용하여 유근평판의 집중하중작용점에서의 응력을 해석하는 방법을 제안하고저 한다.

• 대한기계학회논문집
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• 제18권1호
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• pp.65-76
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• 1994

A higher-oder laminated plate theory including the effect of transverse shear deformation is developed to calculate the gross response and the detailed stress distribution. The theory satisfies the continuity condition of transverse shear stress, and accounts for parabolic variation of the transverse shear stresses through the thickness of each layer. Exact closed-ply laminates are obtained and the results are compared with three-dimensional elasticity solutions and a simple higher-order theory solutions. The results of the present work exhibit acceptable accuracy when compared to the three-dimensional elasticity solutions.

• Structural Engineering and Mechanics
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• 제72권1호
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• pp.131-139
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• 2019

According to the properties of monoclinic materials, the normal and shear stresses are depending on both normal and shear strains. In the current investigation, the static analysis of monoclinic plates based on three dimensional elasticity theory is investigated. New governing equations and boundary conditions are derived for monoclinic plates and the Differential Quadrature Method (DQM) is used to solve the static problem. In our method of solution, no approximation is used and the DQM is adopted in all directions. By showing the differences between our results and the results for especially orthotropic plates, one can find that it is worth to investigate the monoclinic plates to have more accurate results.

• Steel and Composite Structures
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• 제26권5호
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• pp.649-662
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• 2018

In this study, based on the three-dimensional theory of elasticity, free vibration characteristics of sandwich sectorial plates with multiwalled carbon nanotube-(MWCNT)-reinforced composite core are considered. Modified Halpin-Tsai equation is used to evaluate the Young's modulus of the MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. In this paper, free vibration of thick functionally graded sandwich annular sectorial plates with simply supported radial edges and different circular edge conditions including simply supported-clamped, clamped-clamped, and free-clamped is investigated. A semi-analytical approach composed of two-dimensional differential quadrature method and series solution are adopted to solve the equations of motion. The material properties change continuously through the core thickness of the plate, which can vary according to a power-law, exponentially, or any other formulations in this direction. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of laminated sectorial plates.

• Steel and Composite Structures
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• 제25권3호
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• pp.361-374
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• 2017

In this study, the influences of triaxial magnetic field on the wave propagation behavior of anisotropic nanoplates are studied. In order to include small scale effects, nonlocal strain gradient theory has been implemented. To study the nanoplate as a continuum model, the three-dimensional elasticity theory is adopted in Cartesian coordinate. In our study, all the elastic constants are considered and assumed to be the functions of (x, y, z), so all kind of anisotropic structures such as hexagonal and trigonal materials can be modeled, too. Moreover, all types of functionally graded structures can be investigated. eigenvalue method is employed and analytical solutions for the wave propagation are obtained. To justify our methodology, our results for the wave propagation of isotropic nanoplates are compared with the results available in the literature and great agreement is achieved. Five different types of anisotropic structures are investigated in present paper and then the influences of wave number, material properties, nonlocal and gradient parameter and uniaxial, biaxial and triaxial magnetic field on the wave propagation analysis of anisotropic nanoplates are presented. From the best knowledge of authors, it is the first time that three-dimensional elasticity theory and nonlocal strain gradient theory are used together with no approximation to derive the governing equations. Moreover, up to now, the effects of triaxial magnetic field have not been studied with considering size effects in nanoplates. According to the lack of any common approximations in the displacement field or in elastic constant, present theory has the potential to be used as a bench mark for future works.

• Structural Engineering and Mechanics
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• 제39권4호
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• pp.449-463
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• 2011

A free vibration analysis is made of a moderately-thick toroidal shell based on a shear deformation (Timoshenko-Mindlin) shell theory. This work represents an extension of earlier work by the authors which was based on a thin (Kirchoff-Love) shell theory. The analysis uses a modal approach in the circumferential direction, and numerical results are found using the differential quadrature method (DQM). The analysis is first developed for a shell of revolution of arbitrary meridian, and then specialized to a complete circular toroidal shell. A second analysis, based on the three-dimensional theory of elasticity, is presented to cover thick shells. The shear deformation theory is validated by comparing calculated results with previously published results for fifteen cases, found using thin shell theory, moderately-thick shell theory, and the theory of elasticity. Consistent agreement is observed in the comparison of different results. New frequency results are then given for moderately-thick and thick toroidal shells, considered to be completely free. The results indicate the usefulness of the shear deformation theory in determining natural frequencies for toroidal shells.

• Journal of applied mathematics & informatics
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• 제14권1_2호
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• pp.193-212
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• 2004

A new model of generalized thermoelasticity equations for isotropic media with temperature-dependent mechanical properties is established. The modulus of elasticity is taken as a linear function of reference temperature. The present model is described both generalizations, Lord Shulman (L-S) theory with one relaxation time and Green-Lindsay (G-L) with two relaxation times, as well as the coupled theory, instantaneously. The method of the matrix exponential, which constitutes the basis of the state space approach of modern control theory, applied to two-dimensional equations. Laplace and Fourier integral transforms are used. The resulting formulation is applied to a problem of a thick plate subject to heating on parts of the upper and lower surfaces of the plate that varies exponentially with time. Numerical results are given and illustrated graphically for the problem considered. A comparison was made with the results obtained in case of temperature-independent modulus of elasticity in each theory.

• Steel and Composite Structures
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• 제27권2호
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• pp.201-216
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• 2018

In this paper, three-dimensional (3D) elasticity theory in conjunction with nonlocal strain gradient theory (NSGT) is developed for mechanical analysis of anisotropic nanoparticles. The present model incorporates two scale coefficients to examine the mechanical characteristics much accurately. All the elastic constants are considered and assumed to be the functions of (r, ${\theta}$, ${\varphi}$), so all kind of anisotropic structures can be modeled. Moreover, all types of functionally graded spherical structures can be investigated. To justify our model, our results for the radial vibration of spherical nanoparticles are compared with experimental results available in the literature and great agreement is achieved. Next, several examples of the radial vibration and wave propagation in spherical nanoparticles including nonlocal strain gradient parameters are presented for more than 10 different anisotropic nanoparticles. From the best knowledge of authors, it is the first time that 3D elasticity theory and NSGT are used together with no approximation to derive the governing equations in the spherical coordinate. Moreover, up to now, the NSGT has not been used for spherical anisotropic nanoparticles. It is also the first time that all the 36 elastic constants as functions of (r, ${\theta}$, ${\varphi}$) are considered for anisotropic and functionally graded nanostructures including size effects. According to the lack of any common approximations in the displacement field or in elastic constant, present theory can be assumed as a benchmark for future works.

• 한국안전학회지
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• 제11권1호
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• pp.46-52
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• 1996

In this paper, an analytical method is proposed to find the dimensions of impact stresses with using the dimensions of impact loading parameter regardless of mass of impactor, velocity of impactor, and plate thickness. In analytical method of Impulsive stresses, the three-dimensional dynamic theory of elasticity using rectangular coordinates and the potential theory of displacement are utilized, and when the measurement of Impact loading is difficult especially for a steel ball colliding on an infinite plate, the impact loading can be obtained by using the classical plate theory and Hertz’s contact theory. And in the numerical analysis, the fast Fourier transform (F. F. T.) algorithm and the numerical inverse Laplace transformation are used because the analysis of impact loading Is difficult to obtain solutions by using the thress-dimensional dynamic theory of elasticity.