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1 - Free Vibration of Functionally Graded Epoxy/Clay Nanocomposite Beams based on the First Order Shear Deformation Theory
Mahdi Karami KhorramabadiThis paper deals with free vibration of epoxy/clay nanocomposite beams for functionally graded and uniformly distributed of Nanoclay with simply supported conditions at both ends. The specimens were prepared for uniformly distributed of Nanoclay with different Nanoparti أکثرThis paper deals with free vibration of epoxy/clay nanocomposite beams for functionally graded and uniformly distributed of Nanoclay with simply supported conditions at both ends. The specimens were prepared for uniformly distributed of Nanoclay with different Nanoparticles weight percent (pure, 3 wt%, 5 wt% and 7 wt%) and functionally graded distribution. To apply the model of theoretical predictions for the Young modulus, the genetic algorithm procedure was employed for functionally graded and uniformly distributed epoxy/clay nanocomposites and then were compared with the experimental tensile results. The formulation for Young modulus includes the effect of nanoparticles weight fractions and it is modified for functionally graded distribution to take into account the Young modulus as a function of the thickness coordinate. The displacement field of the beam is assumed based on the first order shear deformation beam theory. Applying the Hamilton principle, the governing equations are derived. The influence of nanoparticles on the free vibration frequencies of a beam is presented. To investigate the accuracy of the present analysis, a compression study is carried out with the experimental free vibration results. The results have shown that there is high accuracy for the genetic algorithm procedure for theoretical predictions of the Young modulus and the free vibration frequencies for uniform distribution are generally lower than the corresponding value of the functionally graded distribution. تفاصيل المقالة -
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2 - Free Vibration Analysis of Multi-Layer Rectangular Plate with Two Magneto-Rheological Fluid Layers and a Flexible Core
M Shekarzadeh M.M Najafizadeh P Yousefi A. R Nezamabadi K KhorshidiIn the present article, the free vibration analysis of a multi-layer rectangular plate with two magneto-rheological (MR) fluid layers and a flexible core is investigated based on exponential shear deformation theory for the first time. In exponential shear deformation t أکثرIn the present article, the free vibration analysis of a multi-layer rectangular plate with two magneto-rheological (MR) fluid layers and a flexible core is investigated based on exponential shear deformation theory for the first time. In exponential shear deformation theory, exponential functions are used in terms of thickness coordinate to include the effect of transverse shear deformation and rotary inertia. The displacement of the flexible core is modeled using Frostig’s second order model which contains a polynomial with unknown coefficients. MR fluids viscosity can be varied by changing the magnetic field intensity. Therefore, they have the capability to change the stiffness and damping of a structure. The governing equations of motion have been derived using Hamilton`s principle. The Navier technique is employed to solve derived equations. To validate the accuracy of the derived equations, the results in a specific case are compared with available results in the literature, and a good agreement will be observed. Then, the effect of variation of some parameters such as magnetic field intensity, core thickness to panel thickness ratio and MR layer thickness to panel thickness ratio on natural frequency of the sandwich panel is investigated. تفاصيل المقالة -
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3 - Efficient Higher-Order Shear Deformation Theories for Instability Analysis of Plates Carrying a Mass Moving on an Elliptical Path
E Torkan M PirmoradianThe dynamic performance of structures under traveling loads should be exactly analyzed to have a safe and reasonable structural design. Different higher-order shear deformation theories are proposed in this paper to analyze the dynamic stability of thick elastic plates أکثرThe dynamic performance of structures under traveling loads should be exactly analyzed to have a safe and reasonable structural design. Different higher-order shear deformation theories are proposed in this paper to analyze the dynamic stability of thick elastic plates carrying a moving mass. The displacement fields of different theories are chosen based upon variations along the thickness as cubic, sinusoidal, hyperbolic and exponential. The well-known Hamilton’s principle is utilized to derive equations of motion and then they are solved using the Galerkin method. The energy-rate method is used as a numerical method to calculate the boundary curves separating the stable and unstable regions in the moving mass parameters plane. Effects of the relative plate thickness, trajectories radii and the Winkler foundation stiffness on the system stability are examined. The results obtained in this research are compared, in a special case, with those of the Kirchhoff’s plate model for the validation. تفاصيل المقالة -
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4 - On Static Bending, Elastic Buckling and Free Vibration Analysis of Symmetric Functionally Graded Sandwich Beams
A.S Sayyad P.V AvhadThis article presents Navier type closed-form solutions for static bending, elastic buckling and free vibration analysis of symmetric functionally graded (FG) sandwich beams using a hyperbolic shear deformation theory. The beam has FG skins and isotropic core. Material أکثرThis article presents Navier type closed-form solutions for static bending, elastic buckling and free vibration analysis of symmetric functionally graded (FG) sandwich beams using a hyperbolic shear deformation theory. The beam has FG skins and isotropic core. Material properties of FG skins are varied through the thickness according to the power law distribution. The present theory accounts for a hyperbolic distribution of axial displacement whereas transverse displacement is constant through the thickness i.e effects of thickness stretching are neglected. The present theory gives hyperbolic cosine distribution of transverse shear stress through the thickness of the beam and satisfies zero traction boundary conditions on the top and bottom surfaces of the beam. The equations of the motion are obtained by using the Hamilton’s principle. Closed-form solutions for static, buckling and vibration analysis of simply supported FG sandwich beams are obtained using Navier’s solution technique. The non-dimensional numerical results are obtained for various power law index and skin-core-skin thickness ratios. The present results are compared with previously published results and found in excellent agreement. تفاصيل المقالة -
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5 - Effect of Temperature Dependency on Thermoelastic Behavior of Rotating Variable Thickness FGM Cantilever Beam
M.M.H Mirzaei A Loghman M ArefiThermoelastic behavior of temperature-dependent (TD) and independent (TID) functionally graded variable thickness cantilever beam subjected to mechanical and thermal loadings is studied based on shear deformation theory using a semi-analytical method. Loading is compose أکثرThermoelastic behavior of temperature-dependent (TD) and independent (TID) functionally graded variable thickness cantilever beam subjected to mechanical and thermal loadings is studied based on shear deformation theory using a semi-analytical method. Loading is composed of a transverse distributed force, a longitudinal distributed temperature field due to steady-state heat conduction from root to the tip surface of the beam and an inertia body force due to rotation. A successive relaxation (SR) method for solving temperature-dependent steady-state heat conduction equation is employed to obtain the accurate temperature field. The beam is made of functionally graded material (FGM) in which the mechanical and thermal properties are variable in longitudinal direction based on the volume fraction of constituent. Using first-order shear deformation theory, linear strain–displacement relations and Generalized Hooke’s law, a system of second order differential equation is obtained. Using division method, differential equations are solved for every division. As a result, longitudinal displacement, transverse displacement, and consequently longitudinal stress, shear stress and effective stress are investigated. The results are presented for temperature dependent and independent properties. It has been found that the temperature dependency of the material has a significant effect on temperature distribution, displacements and stresses. This model can be used for thermoelastic analysis of simple turbine blades. تفاصيل المقالة -
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6 - Effect of Winkler Foundation on Radially Symmetric Vibrations of Bi-Directional FGM Non-Uniform Mindlin’s Circular Plate Subjected to In-Plane Peripheral Loading
N Ahlawat R LalAn analysis has been presented of the effect of elastic foundation and uniform in-plane peripheral loading on the natural frequencies and mode shapes of circular plates of varying thickness exhibiting bi-directional functionally graded characteristics, on the basis of f أکثرAn analysis has been presented of the effect of elastic foundation and uniform in-plane peripheral loading on the natural frequencies and mode shapes of circular plates of varying thickness exhibiting bi-directional functionally graded characteristics, on the basis of first order shear deformation theory. The material properties of the plate are varying following a power-law in both the radial and transverse directions. The numerical solutions of the coupled differential equations leading the motion of simply supported and clamped plates acquired by using Hamilton’s principle, is attained by harmonic differential quadrature method. The effect of different plate parameters namely gradient index, heterogeneity parameter, density parameter, taper parameter and thickness parameter is illustrated on the vibration characteristics for the first three modes of vibration for various values of in-plane peripheral loading parameter together with foundation parameter. Critical buckling loads in compression are calculated for both the boundary conditions by putting the frequencies to zero. The reliability of the present technique is confirmed by comparing the results with exact values and results of published work. تفاصيل المقالة -
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7 - Dynamic Stability Analysis of Bi-Directional Functionally Graded Beam with Various Shear Deformation Theories Under Harmonic Excitation and Thermal Environment
A Ghorbanpour Arani Sh Niknejad A Mihankhah I SafariIn this article, dynamic stability analysis of bi-directional functionally graded materials (BDFGMs) beam rested on visco-Pasternak foundation under harmonic excitation is studied. Also, BDFGMs beam is subjected to a transversely uniformly distributed temperature rising أکثرIn this article, dynamic stability analysis of bi-directional functionally graded materials (BDFGMs) beam rested on visco-Pasternak foundation under harmonic excitation is studied. Also, BDFGMs beam is subjected to a transversely uniformly distributed temperature rising and it is assumed that the material properties to be temperature-dependent. According to the exponential and power law distributions, thermo-mechanical properties of BDFGMs beam vary continuously in both the thickness and longitudinal directions. Based on various shear deformation theories (e.g. Euler-Bernoulli, Timoshenko, third order shear deformation and sinusoidal shear deformation theories), the stability equations of BDFGMs beam is derived by applying the Hamilton's principle. The generalized differential quadrature method (GDQM) in conjunction with the Bolotin method is utilized to solve the differential stability equations under SS, SC and CC boundary conditions. To validate the present analysis, a comparison study is carried out with the results found in the literature and a good agreement is observed compared to the reported results. Finally, numerical results are presented to study the influences of the gradient index, length-to-thickness ratio, temperature rise and foundation parameters on the dynamic stability region of BDFGMs beam. The results of presented paper can be used to the optimal design and assessment of the structural failure. تفاصيل المقالة -
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8 - A Novel Spring-Based Model for Damage Investigation of Functionally Graded Beams
S Karimi M Bozorgnsab R Taghipour M.M AlipourIn this paper, free vibration analysis of damaged functionally graded beams based on the first-order shear deformation theory (FSDT) is carried out. In this regard, a new model of springs is introduced to model the damaged elements of the beam. The proposed model is ach أکثرIn this paper, free vibration analysis of damaged functionally graded beams based on the first-order shear deformation theory (FSDT) is carried out. In this regard, a new model of springs is introduced to model the damaged elements of the beam. The proposed model is achieved from stress resultants. The springs equations for homogeneous and functionally graded (FG) beams are presented; furthermore, equations for equivalent springs are also provided which can be used for both homogeneous and FG beams. The proposed method can be applied for the analysis of structures with fewer computation costs and high accuracy. To show the accuracy of the proposed model, the natural frequencies of the beams with real elements and the ones which are modeled by the proposed springs are compared considering various support conditions. Good agreement has been observed. Thereafter, the model is used to detect the damaged elements. The result shows that the model can properly detect the damage location. تفاصيل المقالة -
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9 - Improved High-Order Analysis of Linear Vibrations of a Thick Sandwich Panel With an Electro-Rheological Core by Using Exponential Shear Deformation Theory
M Keshavarzian M.M Najafizadeh K Khorshidi P Yousefi M AlaviIn this paper, the behavior of free vibrations of the thick sandwich panel with multi-layer face sheets and an electrorheological (ER) fluid core using Exponential Shear Deformation Theory were investigated. For the first time, Exponential shear deformation theory is us أکثرIn this paper, the behavior of free vibrations of the thick sandwich panel with multi-layer face sheets and an electrorheological (ER) fluid core using Exponential Shear Deformation Theory were investigated. For the first time, Exponential shear deformation theory is used for the face sheets while the Displacement field based on the second Frostig's model is used for the core. The governing equations and the boundary conditions are derived by Hamilton’s principle. Closed form solution is achieved using the Navier method and solving the eigenvalues. Primary attention is focused on the effects of electric field magnitude, geometric aspect ratio,and ER core layer thickness on the dynamic characteristics of the sandwich plate. The rheological property of an ER material, such as viscosity, plasticity, and elasticity may be changed when applying an electric field. When an electric field is applied, the damping of the system is more effective. The effects of the natural frequencies and loss factors on the dynamic behaviorof the sandwich plate are studied.the natural frequency of the sandwich plate increases and the modal loss factor decreases. With increasing the thickness of the ER layer, the natural frequencies of the sandwich plate are decreased. تفاصيل المقالة -
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10 - Analysis of a Functionally Graded Finite Wedge Under Antiplane Deformation
A. R Shahani I ShakeriThe antiplane deformation of a wedge made of a functionally graded material (FGM) with finite radius has been investigated analytically in the present article. In relation to the boundary conditions imposed on the arc portion of the wedge, displacement or traction, two أکثرThe antiplane deformation of a wedge made of a functionally graded material (FGM) with finite radius has been investigated analytically in the present article. In relation to the boundary conditions imposed on the arc portion of the wedge, displacement or traction, two problems have been studied. In each of the problems three various kinds of boundary conditions (traction-displacement, displacement-displacement and traction-traction) have been applied to the radial edges of the wedge. The governing differential equations have been solved by employing finite Fourier transforms and Green’s function method. The closed form solutions for stress and displacement distribution have been achieved for the whole domain. Explicit relations have been extracted for the order of stress singularity in all cases. These relations indicated the dependence of the order of stress singularity on the boundary conditions, material property and wedge angle. In fact, despite of an isotropic wedge, for which the order of stress singularity depends only the geometry of the wedge, in an FG wedge the order of stress singularity depends both the geometry as well as the material property. تفاصيل المقالة -
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11 - Bending Analysis of Laminated Composite Plates with Arbitrary Boundary Conditions
A.M Naserian Nik M TahaniIt is well known that for laminated composite plates a Levy-type solution exists only for cross-ply and antisymmetric angle-ply laminates. Numerous investigators have used the Levy method to solve the governing equations of various equivalent single-layer plate theories أکثرIt is well known that for laminated composite plates a Levy-type solution exists only for cross-ply and antisymmetric angle-ply laminates. Numerous investigators have used the Levy method to solve the governing equations of various equivalent single-layer plate theories. It is the intension of the present study to introduce a method for analytical solutions of laminated composite plates with arbitrary lamination and boundary conditions subjected to transverse loads. The method is based on separation of spatial variables of displacement field components. Within the displacement field of a first-order shear deformation theory (FSDT), a laminated plate theory is developed. Two systems of coupled ordinary differential equations with constant coefficients are obtained by using the principle of minimum total potential energy. Since the procedure used is simple and straightforward it can, therefore, be adopted in developing higher-order shear deformation and layerwise laminated plate theories. The obtained equations are solved analytically using the state-space approach. The results obtained from the present method are compared with the Levy-type solutions of cross-ply and antisymmetric angle-ply laminates with various admissible boundary conditions to verify the validity and accuracy of the present theory. Also for other laminations and boundary conditions that there exist no Levy-type solutions the present results may be compared with those obtained from finite element method. It is seen that the present results have excellent agreements with those obtained by Levy-type method. تفاصيل المقالة -
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12 - Elastic Buckling of Moderately Thick Homogeneous Circular Plates of Variable Thickness
S.K Jalali M.H NaeiIn this study, the buckling response of homogeneous circular plates with variable thickness subjected to radial compression based on the first-order shear deformation plate theory in conjunction with von-Karman nonlinear strain-displacement relations is investigated. Fu أکثرIn this study, the buckling response of homogeneous circular plates with variable thickness subjected to radial compression based on the first-order shear deformation plate theory in conjunction with von-Karman nonlinear strain-displacement relations is investigated. Furthermore, optimal thickness distribution over the plate with respect to buckling is presented. In order to determine the distribution of the prebuckling load along the radius, the membrane equation is solved using the shooting method. Subsequently, employing the pseudospectral method that makes use of Chebyshev polynomials, the stability equations are solved. The influence of the boundary conditions, the thickness variation profile and aspect ratio on the buckling behavior is examined. The comparison shows that the results derived, using the current method, compare very well with those available in the literature. تفاصيل المقالة -
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13 - An Efficient Co Finite Element Approach for Bending Analysis of Functionally Graded Ceramic-Metal Skew Shell Panels
G Taj A ChakrabartiIn this article, the prominence has been given to study the influence of skew angle on bending response of functionally graded material shell panels under thermo-mechanical environment. Derivation of governing equations is based on the Reddy’s higher-order shear d أکثرIn this article, the prominence has been given to study the influence of skew angle on bending response of functionally graded material shell panels under thermo-mechanical environment. Derivation of governing equations is based on the Reddy’s higher-order shear deformation theory and Sander’s kinematic equations. To circumvent the problem of C1 continuity requirement coupled with the finite element implementation, C0 formulation is developed. A nine noded isoparametric Lagrangian element has been employed to mesh the proposed shell element in the framework of finite element method. Bending response of functionally graded shell under thermal field is accomplished by exploiting temperature dependent properties of the constituents. Arbitrary distribution of the elastic properties follows linear distribution law which is a function of the volume fraction of ingredients. Different combinations of ceramic-metal phases are adopted to perform the numerical part. Different types of shells (cylindrical, spherical, hyperbolic paraboloid and hypar) and shell geometries are concerned to engender new-fangled results. Last of all, the influence of various parameters such as thickness ratio, boundary condition, volume fraction index and skew angle on the bending response of FGM skew shell is spotlighted. Some new results pertain to functionally graded skew shells are reported for the first time, which may locate milestone in future in the vicinity of functionally graded skew shells. تفاصيل المقالة -
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14 - A Static Flexure of Thick Isotropic Plates Using Trigonometric Shear Deformation Theory
Y.M Ghugal A.S SayyadA Trigonometric Shear Deformation Theory (TSDT) for the analysis of isotropic plate, taking into account transverse shear deformation effect as well as transverse normal strain effect, is presented. The theory presented herein is built upon the classical plate theory. I أکثرA Trigonometric Shear Deformation Theory (TSDT) for the analysis of isotropic plate, taking into account transverse shear deformation effect as well as transverse normal strain effect, is presented. The theory presented herein is built upon the classical plate theory. In this displacement-based, trigonometric shear deformation theory, the in-plane displacement field uses sinusoidal function in terms of thickness coordinate to include the shear deformation effect. The cosine function in terms of thickness coordinate is used in transverse displacement to include the effect of transverse normal strain. It accounts for realistic variation of the transverse shear stress through the thickness and satisfies the shear stress free surface conditions at the top and bottom surfaces of the plate. The theory obviates the need of shear correction factor like other higher order or equivalent shear deformation theories. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. Results obtained for static flexural analysis of simply supported thick isotropic plates for various loading cases are compared with those of other refined theories and exact solution from theory of elasticity. تفاصيل المقالة -
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15 - Vibration Analysis of Functionally Graded Spinning Cylindrical Shells Using Higher Order Shear Deformation Theory
M MehrparvarIn this paper the vibration of a spinning cylindrical shell made of functional graded material is investigated. After a brief introduction of FG materials, by employing higher order theory for shell deformation, constitutive relationships are derived. Next, governing di أکثرIn this paper the vibration of a spinning cylindrical shell made of functional graded material is investigated. After a brief introduction of FG materials, by employing higher order theory for shell deformation, constitutive relationships are derived. Next, governing differential equation of spinning cylindrical shell is obtained through utilizing energy method and Hamilton’s principle. Making use of the principle of minimum potential energy, the characteristic equation of natural frequencies is derived. After verification of the results, the effect of changing different parameters such as material grade, geometry of shell and spinning velocity on the natural frequency are examined. تفاصيل المقالة -
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16 - Free Vibration of Thick Isotropic Plates Using Trigonometric Shear Deformation Theory
Y.M Ghugal A.S SayyadIn this paper a variationally consistent trigonometric shear deformation theory is presented for the free vibration of thick isotropic square and rectangular plate. In this displacement based theory, the in-plane displacement field uses sinusoidal function in terms of t أکثرIn this paper a variationally consistent trigonometric shear deformation theory is presented for the free vibration of thick isotropic square and rectangular plate. In this displacement based theory, the in-plane displacement field uses sinusoidal function in terms of thickness coordinate to include the shear deformation effect. The cosine function in terms of thickness coordinate is used in transverse displacement to include the effect of transverse normal strain. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. Results of frequency of bending mode, thickness-shear mode and thickness-stretch mode are obtained from free vibration of simply supported isotropic square and rectangular plates and compared with those of other refined theories and frequencies from exact theory. Present theory yields exact dynamic shear correction factor π2/12 from thickness shear motion of the plate. تفاصيل المقالة -
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17 - Comparison of Two Kinds of Functionally Graded Cylindrical Shells with Various Volume Fraction Laws for Vibration Analysis
M.R Isvandzibaei P.J AwasareIn this paper, a study on the vibration of thin cylindrical shells made of a functionally gradient material (FGM) composed of stainless steel and nickel is presented. The effects of the FGM configuration are taken into account by studying the frequencies of two FG cylin أکثرIn this paper, a study on the vibration of thin cylindrical shells made of a functionally gradient material (FGM) composed of stainless steel and nickel is presented. The effects of the FGM configuration are taken into account by studying the frequencies of two FG cylindrical shells. Type I FG cylindrical shell has nickel on its inner surface and stainless steel on its outer surface and Type II FG cylindrical shell has stainless steel on its inner surface and nickel on its outer surface. The study is carried out based on third order shear deformation shell theory (TSDT). The objective is to study the natural frequencies, the influence of constituent volume fractions and the effects of configurations of the constituent materials on the frequencies. The properties are graded in the thickness direction according to the volume fraction power-law distribution. The analysis is carried out with strains-displacement relations from Love's shell theory. The governing equations are obtained using energy functional with the Rayleigh-Ritz method. Results are presented on the frequency characteristics and the influences of constituent various volume fractions for Type I and II FG cylindrical shells and simply supported boundary conditions on the frequencies. تفاصيل المقالة -
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18 - Displacements and Stresses in Pressurized Thick FGM Cylinders with Varying Properties of Power Function Based on HSDT
M Ghannad H GharooniUsing the infinitesimal theory of elasticity and analytical formulation, displacements and stresses based on the high-order shear deformation theory (HSDT) is presented for axisymmetric thick-walled cylinders made of functionally graded materials under internal and/or ex أکثرUsing the infinitesimal theory of elasticity and analytical formulation, displacements and stresses based on the high-order shear deformation theory (HSDT) is presented for axisymmetric thick-walled cylinders made of functionally graded materials under internal and/or external uniform pressure. The material is assumed to be isotropic heterogeneous with constant Poisson’s ratio and radially varying elastic modulus continuously along the thickness with a power function. At first, general governing equations of the FGM thick cylinders are derived by assumptions of the high-order shear deformation theory. Following that, the set of non-homogenous linear differential equations with constant coefficients, for the cylinder under the generalized clamped-clamped conditions have been solved analytically and the effect of loading and inhomogeneity on the stresses and displacements have been investigated. The results are compared with the findings of both first-order shear deformation theory (FSDT) and finite element method (FEM). Finally, the effects of higher order approximations on the stresses and displacements have been studied. تفاصيل المقالة -
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19 - The Effect of Elastic Foundations on the Buckling Behavior of Functionally Graded Carbon Nanotube-Reinforced Composite Plates in Thermal Environments Using a Meshfree Method
Sh Shams B Soltani M Memar ArdestaniThe buckling behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates resting on Winkler-Pasternak elastic foundations under in-plane loads for various temperatures is investigated using element-free Galerkin (EFG) method based on first-ord أکثرThe buckling behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates resting on Winkler-Pasternak elastic foundations under in-plane loads for various temperatures is investigated using element-free Galerkin (EFG) method based on first-order shear deformation theory (FSDT). The modified shear correction factor is used based on energy equivalence principle. Carbon nanotubes (CNTs) are embedded in polymer matrix and distributed in four types of arrangements. The temperature-dependent material properties of an FG-CNTRC plate are assumed to be graded along the thickness direction of the plate and estimated through a micromechanical model based on the extended rule of mixture. Full transformation approach is employed to enforce essential boundary conditions. The modified shear correction factor is utilized based on energy equivalence principle involving the actual non-uniform shear stress distribution through the thickness of the FG-CNTRC plate. The accuracy and convergency of the EFG method is established by comparing the obtained results with available literature. Moreover, the effects of elastic foundation parameters are investigated for various boundary conditions, temperatures, plate width-to-thickness and aspect ratios, and CNT distributions and volume fractions. Detailed parametric studies demonstrate that the elastic foundation parameters, CNT distributions along the thickness direction of the plate and the temperature change have noticeable effects on buckling behavior of carbon nanotube-reinforced composite (CNTRC) plates. تفاصيل المقالة -
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20 - Smart Vibration Control of Magnetostrictive Nano-Plate Using Nonlocal Continuum Theory
A Ghorbanpour Arani Z Khoddami Maraghi H Khani AraniIn this research, a control feedback system is used to study the free vibration response of rectangular plate made of magnetostrictive material (MsM) for the first time. A new trigonometric higher order shear deformation plate theory are utilized and the results of them أکثرIn this research, a control feedback system is used to study the free vibration response of rectangular plate made of magnetostrictive material (MsM) for the first time. A new trigonometric higher order shear deformation plate theory are utilized and the results of them are compared with two theories in order to clarify their accuracy and errors. Pasternak foundation is selected to modelling of elastic medium due to considering both normal and shears modulus. Also in-plane forces are uniformly applied on magnetostrictive nano-plate (MsNP) in x and y directions. Nonlocal motion equations are derived using Hamilton’s principle and solved by differential quadrature method (DQM) considering different boundary conditions. Results indicate the effect of various parameters such as aspect ratio, thickness ratio, elastic medium, compression and tension loads and small scale effect on vibration behaviour of MsNP especially the controller effect of velocity feedback gain to minimizing the frequency. These finding can be used to active noise and vibration cancellation systems in micro and nano smart structures. تفاصيل المقالة -
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21 - Third Order Formulation for Vibrating Non-Homogeneous Cylindrical Shells in Elastic Medium
M Gheisari H Molatefi S.S AhmadiThird order shear deformation theory of cylindrical shells is employed to investigate the vibration characteristics of non-homogeneous cylindrical shells surrounded by an elastic medium. The kinematic relations are obtained using the strain-displacement relations of Don أکثرThird order shear deformation theory of cylindrical shells is employed to investigate the vibration characteristics of non-homogeneous cylindrical shells surrounded by an elastic medium. The kinematic relations are obtained using the strain-displacement relations of Donnell shell theory. The shell properties are considered to be dependent on both position and thermal environment. A suitable function through the thickness direction is assumed for the non-homogeneity property. The Winkler-Pasternak elastic foundation is used to model the elastic medium. Analytical solutions are presented for cylindrical shells with simply supported boundary conditions. From the numerical studies, it is revealed that, the natural frequencies are affected significantly by the elastic foundation coefficients and environmental temperature conditions. تفاصيل المقالة -
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22 - Response Determination of a Beam with Moderately Large Deflection Under Transverse Dynamic Load Using First Order Shear Deformation Theory
F Sohani H.R EipakchiIn the presented paper, the governing equations of a vibratory beam with moderately large deflection are derived using the first order shear deformation theory. The beam is homogenous, isotropic and it is subjected to the dynamic transverse and axial loads. The kinemati أکثرIn the presented paper, the governing equations of a vibratory beam with moderately large deflection are derived using the first order shear deformation theory. The beam is homogenous, isotropic and it is subjected to the dynamic transverse and axial loads. The kinematic of the problem is according to the Von-Karman strain-displacement relations and the Hook's law is used as the constitutive equation. These equations which are a system of nonlinear partial differential equations with constant coefficients are derived by using the Hamilton’s principle. The eigenfunction expansion method and the perturbation technique are applied to obtain the response. The results are compared with the finite elements method. تفاصيل المقالة -
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23 - Vibration Analysis of FG Nanoplate Based on Third-Order Shear Deformation Theory (TSDT) and Nonlocal Elasticity
M.M Najafizadeh M Raki P YousefiIn present study, the third-order shear deformation theory has been developed to investigate vibration analysis of FG Nano-plates based on Eringen nonlocal elasticity theory. The materials distribution regarding to the thickness of Nano-plate has been considered based o أکثرIn present study, the third-order shear deformation theory has been developed to investigate vibration analysis of FG Nano-plates based on Eringen nonlocal elasticity theory. The materials distribution regarding to the thickness of Nano-plate has been considered based on two different models of power function and exponential function. All equations governing on the vibration of FG Nano-plate have been derived from Hamilton’s principle. It has been also obtained the analytical solution for natural frequencies and corresponding mode shapes of simply supported FG Nano-plates. In addition, the general form of stiffness and mass matrix elements has been expressed based on this theory. The effect of different parameters such as power and exponential indexes of targeted function , nonlocal parameter of Nano-plate, aspect ratio and thickness to length ratio of Nano-plate on non-dimensional natural frequencies of free vibration responses have been investigated. The obtained analytical results show an excellent agreement with other available solutions of previous studies. The formulation and analytical results obtained from proposed method can be used as a benchmark for further studies to develop this area of research. تفاصيل المقالة -
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24 - Spectral Finite Element Method for Free Vibration of Axially Moving Plates Based on First-Order Shear Deformation Theory
M.R Bahrami S HatamiIn this paper, the free vibration analysis of moderately thick rectangular plates axially moving with constant velocity and subjected to uniform in-plane loads is investigated by the spectral finite element method. Two parallel edges of the plate are assumed to be simpl أکثرIn this paper, the free vibration analysis of moderately thick rectangular plates axially moving with constant velocity and subjected to uniform in-plane loads is investigated by the spectral finite element method. Two parallel edges of the plate are assumed to be simply supported and the remaining edges have any arbitrary boundary conditions. Using Hamilton’s principle, three equations of motion for the plate are developed based on first-order shear deformation theory. The equations are transformed from the time domain into the frequency domain by assuming harmonic solutions. Then, the frequency-dependent dynamic shape functions obtained from the exact solution of the governing differential equations is used to develop the spectral stiffness matrix. By solving a non-standard eigenvalue problem, the natural frequencies and the critical speeds of the moving plates are obtained. The exactness and validity of the results are verified by comparing them with the results in previous studies. By the developed method some examples for vibration of stationary and moving moderately thick plates with different boundary conditions are presented. The effects of some parameters such as the axially speed of plate motion, the in-plane forces, aspect ratio and length to thickness ratio on the natural frequencies and the critical speeds of the moving plate are investigated. These results can be used as a benchmark for comparing the accuracy and precision of the other analytical and numerical methods. تفاصيل المقالة -
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25 - New Method for Large Deflection Analysis of an Elliptic Plate Weakened by an Eccentric Circular Hole
Sh Dastjerdi L YazdanparastThe bending analysis of moderately thick elliptic plates weakened by an eccentric circular hole has been investigated in this article. The nonlinear governing equations have been presented by considering the von-Karman assumptions and the first-order shear deformation t أکثرThe bending analysis of moderately thick elliptic plates weakened by an eccentric circular hole has been investigated in this article. The nonlinear governing equations have been presented by considering the von-Karman assumptions and the first-order shear deformation theory in cylindrical coordinates system. Semi-analytical polynomial method (SAPM) which had been presented by the author before has been used. By applying SAPM method, the nonlinear partial differential equations have been transformed to the nonlinear algebraic equations system. Then, the nonlinear algebraic equations have been solved by using Newton–Raphson method. The obtained results of this study have been compared with the results of other references and the accuracy of the results has been shown. The effect of some important parameters on the results such as the location of the circular hole, the ratio of major to minor radiuses of elliptical plate, the size of circular hole and boundary conditions have been studied. It is concluded that applying the presented method is very convenient and efficient. So, it can be used for analyzing the mechanical behavior of elliptical plates, instead of relatively complicated formulations in elliptic coordinates system. تفاصيل المقالة -
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26 - Free Vibration of Functionally Graded Cylindrical Shell Panel With and Without a Cutout
k.S Sai Ram K Pratyusha P KiranmayiThe free vibration analysis of the functionally graded cylindrical shell panels with and without cutout is carried out using the finite element method based on a higher-order shear deformation theory. A higher-order theory is used to properly account for transverse shea أکثرThe free vibration analysis of the functionally graded cylindrical shell panels with and without cutout is carried out using the finite element method based on a higher-order shear deformation theory. A higher-order theory is used to properly account for transverse shear deformation. An eight noded degenerated isoparametric shell element with nine degrees of freedom at each node is considered. The stiffness and mass matrices are derived based on the principle of minimum potential energy. The stiffness and mass matrices of the element are evaluated by performing numerical integration using the Gaussian quadrature. The effect of volume fraction exponent on the fundamental natural frequency of simply supported and clamped functionally graded cylindrical shell panel without a cutout is studied for various aspect ratios and arc-length to thickness ratios. Results are presented for variation of the fundamental natural frequency of the cylindrical shell panel with cutout size for simply supported and clamped boundary conditions. تفاصيل المقالة -
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27 - Analysis of Viscoelastic Functionally Graded Sandwich Plates with CNT Reinforced Composite Face Sheets on Viscoelastic Foundation
A Ghorbanpour Arani M Emdadi H Ashrafi M Mohammadimehr S Niknejad A.A Ghorbanpour Arani A HosseinpourIn this article, bending, buckling, and free vibration of viscoelastic sandwich plate with carbon nanotubes reinforced composite facesheets and an isotropic homogeneous core on viscoelastic foundation are presented using a new first order shear deformation theory. Accor أکثرIn this article, bending, buckling, and free vibration of viscoelastic sandwich plate with carbon nanotubes reinforced composite facesheets and an isotropic homogeneous core on viscoelastic foundation are presented using a new first order shear deformation theory. According to this theory, the number of unknown’s parameters and governing equations are reduced and also the using of shear correction factor is not necessary because the transverse shear stresses are directly computed from the transverse shear forces by using equilibrium equations. The governing equations obtained using Hamilton’s principle is solved for a rectangular viscoelastic sandwich plate. The effects of the main parameters on the vibration characteristics of the viscoelastic sandwich plates are also elucidated. The results show that the frequency significantly decreases with using foundation and increasing the viscoelastic structural damping coefficient as well as the damping coefficient of materials and foundation. تفاصيل المقالة -
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28 - Investigation of Pre-buckling Stress Effect on Buckling Load Determination of Finite Rectangular Plates with Circular Cutout
S Abolghasemi H.R Eipakchi M ShariatiThis paper investigates the buckling of finite isotropic rectangular plates with circular cutout under uniaxial and biaxial loading. The complex potential method is used to calculate the pre-buckling stress distribution around the cutout in the plate with finite dimensi أکثرThis paper investigates the buckling of finite isotropic rectangular plates with circular cutout under uniaxial and biaxial loading. The complex potential method is used to calculate the pre-buckling stress distribution around the cutout in the plate with finite dimensions. To satisfy the in-plane boundary conditions, the generalized complex-potential functions are introduced and a new method based on the boundary integral which has been obtained from the principle of virtual work is used to apply the boundary conditions at the plate edges. The potential energy of the plate is calculated by considering the first order shear deformation theory and the Ritz method is used to calculate the buckling load. The effects of cutout size, type of loading and different boundary conditions on the buckling load are investigated. Comparing of the calculated buckling loads with the finite element results shows the accuracy of the presented method for buckling analysis of the plates. تفاصيل المقالة -
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29 - Non-Local Thermo-Elastic Buckling Analysis of Multi-Layer Annular/Circular Nano-Plates Based on First and Third Order Shear Deformation Theories Using DQ Method
Sh Dastjerdi M JabbarzadehIn present study, thermo-elastic buckling analysis of multi-layer orthotropic annular/circular graphene sheets is investigated based on Eringen’s theory. The moderately thick and also thick nano-plates are considered. Using the non-local first and third order shea أکثرIn present study, thermo-elastic buckling analysis of multi-layer orthotropic annular/circular graphene sheets is investigated based on Eringen’s theory. The moderately thick and also thick nano-plates are considered. Using the non-local first and third order shear deformation theories, the governing equations are derived. The van der Waals interaction between the layers is simulated for multi-layer sheets. The stability governing equations are obtained according to the adjacent equilibrium estate method. The constitutive equations are solved by applying the differential quadrature method (DQM). Applying the differential quadrature method, the ordinary differential equations are transformed to algebraic equations. Then, the critical temperature is obtained. Since there is not any research in thermo-elastic buckling analysis of multi-layer graphene sheets, the results are validated with available single layer articles. The effects of non-local parameter, the values of van der Waals interaction between the layers, third to first order shear deformation theory analyses, non-local to local analyses, different values of Winkler and Pasternak elastic foundation and analysis of bi-layer and triple layer sheets are investigated. It is concluded that the critical temperature increases and tends to a constant value along the rise of van der Waals interaction between the layers. تفاصيل المقالة -
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30 - Free and Forced Transverse Vibration Analysis of Moderately Thick Orthotropic Plates Using Spectral Finite Element Method
M.R Bahrami S HatamiIn the present study, a spectral finite element method is developed for free and forced transverse vibration of Levy-type moderately thick rectangular orthotropic plates based on first-order shear deformation theory. Levy solution assumption was used to convert the two- أکثرIn the present study, a spectral finite element method is developed for free and forced transverse vibration of Levy-type moderately thick rectangular orthotropic plates based on first-order shear deformation theory. Levy solution assumption was used to convert the two-dimensional problem into a one-dimensional problem. In the first step, the governing out-of-plane differential equations are transformed from time domain into frequency domain by discrete Fourier transform theory. Then, the spectral stiffness matrix is formulated, using frequency-dependent dynamic shape functions which are obtained from the exact solution of the governing differential equations. An efficient numerical algorithm, using drawing method is used to extract the natural frequencies. The frequency domain dynamic responses are obtained from solution of the spectral element equation. Also, the time domain dynamic responses are derived by using inverse discrete Fourier transform algorithm. The accuracy and excellent performance of the spectral finite element method is then compared with the results obtained from closed form solution methods in previous studies. Finally, comprehensive results for out-of-plane natural frequencies and transverse displacement of the moderately thick rectangular plates with six different combinations of boundary conditions are presented. These results can serve as a benchmark to compare the accuracy and precision of the numerical methods used. تفاصيل المقالة -
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31 - تحلیل خیز و تنش در ورق های مرکب لایهای با استفاده از تئوری برشی و تابع سکانت
ایمان نجیمی سعید جعفری مهرآبادی پیمان یوسفیکاربردهای روز افزون مواد مرکب در صنایع مختلف ازجمله هوافضا، کشتیسازی و سازههایی در ابعاد میکرو و ماکرو باعث شده که محققان این حیطه توجه خاصی بر طراحی این سازهها را داشته باشند. در پژوهش حاضر به تحلیل استاتیکی یک ورق مستطیلی به کمک حالتی خاص از تئوری مرتبه بالای تغیر أکثرکاربردهای روز افزون مواد مرکب در صنایع مختلف ازجمله هوافضا، کشتیسازی و سازههایی در ابعاد میکرو و ماکرو باعث شده که محققان این حیطه توجه خاصی بر طراحی این سازهها را داشته باشند. در پژوهش حاضر به تحلیل استاتیکی یک ورق مستطیلی به کمک حالتی خاص از تئوری مرتبه بالای تغیر شکل برشی با در نظر گرفتن تابع سکانت در میدان تغییر مکان، پرداختهشده است. معادلههای ورق کامپوزیت لایهای مورداستفاده در این پژوهش به کمک رابطهی حساب تغییرات و اصل همیلتون با تشکیل ترمهای مختلف انرژی سیستم بهدستآمده . برای حل معادلات حاکم از روش ناویر با جوابهایی متشکل از توابع سینوسی و کسینوسی و با در نظر گرفتن شرایط مرزی سیستم استفادهشده است. با حل معادلات مذکور مقادیر خیز ورق با توجه به تغییر در پارامترهای سیستم محاسبهشده است و جوابهای بهدستآمده با نتایج مندرج در مقالات معتبر چاپشده مقایسه و از صحت آنها اطمینان کافی حاصلشده است. در خاتمه نتیجه شده که تحلیل خیز به کمک توابع سکانت بسیار نزدیک به جوابهای حاصلشده از پژوهشهای مشابه است و در موارد خاص میتوان از این توابع استفاده نمود. تفاصيل المقالة -
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32 - Implementation of Higher Order Shear Theory on Isotropic Material and Liu's Bending Part on Laminated Composite Flat Shell Elements
Taufiq Rochman Agoes Soehadjono Achfas ZacoebPlate and shell analysis using classical plate theory (CPT) has a lack of accuracy in predicting the influence of transverse deformation, because of its assumption that the line normal to the surface is remain straight and normal to the midplane before and after deforma أکثرPlate and shell analysis using classical plate theory (CPT) has a lack of accuracy in predicting the influence of transverse deformation, because of its assumption that the line normal to the surface is remain straight and normal to the midplane before and after deformation. The next revision by constant shear deformation theory or famous as first order shear deformation theory (CSDT/FOSDT) still suffer a disadvantage that have a constant value in the shear term that called shear locking phenomenon. This matter have been corrected by higher order shear deformation theory (HOSDT) using refined assumption that the line normal to the surface should be in a parabolic function and not normal to the midplane, but normal to the surfaces so it fulfill the zero strain in the surfaces. The analysis of bending part of laminated composite flat shell element is applied by higher order lamination theory (HOLT) that adopted from HOSDT. This model is accurate for thicknesses variation and complex material. HOLT model is implemented into finite element procedure to find deflection, stresses and internal forces. It can be concluded that the displacement and stresses in HOLT model is higher than FOLT ones (first order lamination theory) in small ratio of a/h dan its result almost the same value for a/h ratio more than 10. In a square plate case, the displacement get smaller if the fiber arranged into cross-ply sequence. Interlaminar stresses along thickness is not distributed continuously, but they have certain modes that depend on the depth of point position, the lamina or layer number, fiber orthotropic angle of each layer and a/h ratio. تفاصيل المقالة -
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33 - A FSDT model for vibration analysis of Nano rectangular FG plate based on Modified Couple Stress Theory under moving load
یونس امینIn present paper, vibration of Nano FGM plate based on modified couple stress and First Order Shear Deformation Theories (FSDT) under moving load has been developed. Basic equations and linear strains are introduced by first order shear deformation theory and Mori Tanak أکثرIn present paper, vibration of Nano FGM plate based on modified couple stress and First Order Shear Deformation Theories (FSDT) under moving load has been developed. Basic equations and linear strains are introduced by first order shear deformation theory and Mori Tanaka’s model is used for the plate. The module of elasticity and density are assumed to vary only through thickness of plate. Governing Equations are derived according to the modified couple stress theory and Hamilton’s principle. Constitutive equations are also derived based on modified couple stress and finally, analytical solution for simply supported Nano rectangular FG plate is obtained by using of Navier solution. Examples of length scales parameter and power law index are presented to show effect of this parameter on plate behaviors. Results show that plate’s deflection enhances with power law index increasing and by increasing of length scale parameter, deflection decreases, and for frequencies, the deflection with both raising of power law index and length parameter scales, are reduced تفاصيل المقالة -
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34 - The Effect of Parameters of Winkler-Pasternak Elastic Foundations on Stress Analysis of Rectangular Plates Subjected to a Moving Load
احمدرضا خورشیدوند علی خیری امیر مسعود الله قلیIn this study, the stress analysis of rectangular plates resting on Winkler Pasternak model of elastic foundations under a movingconcentrated load with constant velocity and the impact of parameters related to the elastic foundations on normal stresses areinvestigated. أکثرIn this study, the stress analysis of rectangular plates resting on Winkler Pasternak model of elastic foundations under a movingconcentrated load with constant velocity and the impact of parameters related to the elastic foundations on normal stresses areinvestigated. The strain components are assumed to be linear and the Poisson’s ratio is kept constant. Based on first order sheardeformation theory (FSDT) and by employing Hamilton’s principle, the theoretical equations of motion and boundary conditionsare derived. Dimensionless discrete equations and boundary conditions have been achieved by using two dimensional generalizeddifferential quadrature method (DQM) and Newmark procedure. The convergence and accuracy of the present formulation andmethod of the solution, where possible, are demonstrated by comparing with the work of other investigators. With these results,the effect of Winkler foundation modulus and stiffness of Pasternak shear layer foundations on normal stresses of plates havebeen investigated. The analysis provides for both simply supported and clamped boundary conditions at edges. It is discoveredthat the Pasternak shear layer has a predominant influence over Winkler elastic modulus on the plates. تفاصيل المقالة -
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35 - Non-Linear Analysis of Viscoelastic Rectangular Plates Subjected to In-Plane Compression
منوچهر صالحی امین صفی جهان شاهیGeometrically nonlinear governing equations for a plate with linear viscoelastic material are derived. The material model is of Boltzmann superposition principle type. A third-order displacement field is used to model the shear deformation effects. For the solution of أکثرGeometrically nonlinear governing equations for a plate with linear viscoelastic material are derived. The material model is of Boltzmann superposition principle type. A third-order displacement field is used to model the shear deformation effects. For the solution of the nonlinear governing equations the Dynamic Relaxation (DR) iterative method together with the finite difference discretization technique is used. Finally, the numerical results for the critical buckling load for simply supported edge constraints are reported. In order to justify the accuracy of the results, the elastic plate critical buckling loads are obtained and compared with the existing results. The correlations are very satisfactory. The numerical results are presented for Classical Plate Theory (CPT), First order- Shear Defonmation Plate Theory (FSDT) and Higher Order- Shear Deformation Plate Theory (HSDT). In the case of thick plate the differences among the three theories are highlighted, however, for thin plate the variations are very small. تفاصيل المقالة -
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36 - Forced Vibration Analysis of Functionally Graded Rectangular Plates with Porosities under a Moving Load
احمدرضا خورشیدوند علی خیریIn this paper, vibration behaviors of functionally graded rectangular plates with porosity under a moving concentrated load are considered. Mechanical properties such as elasticity modulus and density of functionally graded (FG) plates are varied as power-law, while Poi أکثرIn this paper, vibration behaviors of functionally graded rectangular plates with porosity under a moving concentrated load are considered. Mechanical properties such as elasticity modulus and density of functionally graded (FG) plates are varied as power-law, while Poisson’s ratio is kept constant and porosity as two types of evenly distribution (porosity-I) and unevenly distribution (porosity-II) is assumed. Based on first order shear deformation theory (FSDT) and by employing Hamilton’s principle, the theoretical equations of motion and boundary conditions are derived. Dimensionless discrete equations have been achieved by using generalized differential quadrature method and Newmark procedure. The convergence and accuracy of the present formulation and method of the solution are demonstrated. The effect of volume fraction index, porosity volume fraction and distribution pattern on displacements of plates have been investigated. It is discovered that the volume fraction index has a significant effect on the deflection of the plates and the porosity volume fraction influences more significantly on deflection of porous FG plates in porosity-I than in porosity-II. تفاصيل المقالة -
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37 - Vibration Analysis of FG Micro-Beam Based on the Third Order Shear Deformation and Modified Couple Stress Theories
Mehdi Alimoradzadeh Mehdi Salehi Sattar Mohammadi EsfarjaniIn this paper, free vibration analysis and forced vibration analysis of FG doubly clamped micro-beams is studied based on the third order shear deformation and modified couple stress theories. The size dependent dynamic equilibrium equations and both the classical and n أکثرIn this paper, free vibration analysis and forced vibration analysis of FG doubly clamped micro-beams is studied based on the third order shear deformation and modified couple stress theories. The size dependent dynamic equilibrium equations and both the classical and non-classical boundary conditions are derived using a variational approach. It is assumed that all properties of the FG micro-beam follow a power law form through thickness. The motion equations are solved by employing Furrier series in conjunction with Galerkin method. Also, effects of aspect ratio, power index and dimensionless length scale parameter on the natural frequencies and amplitude-excite frequency curves are investigated. Findings indicate that dimensionless frequencies are strongly dependent on the values of the material length scale parameter and power index. The numerical results of this study indicate that if the thickness of the beam is in the order of the material length scale parameter, size effects are more significant. تفاصيل المقالة -
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38 - Structural Analysis of Unsymmetric Laminated Composite Timoshenko Beam Subjected to Moving Load
Mohammad Javad RezvaniThe structural analysis of an infinite unsymmetric laminated composite Timoshenko beam over Pasternak viscoelastic foundation under moving load is studied. The beam is subjected to a travelling concentrated load. Closed form steady state solutions, based on the first-or أکثرThe structural analysis of an infinite unsymmetric laminated composite Timoshenko beam over Pasternak viscoelastic foundation under moving load is studied. The beam is subjected to a travelling concentrated load. Closed form steady state solutions, based on the first-order shear deformation theory (FSDT) are developed. In this analysis, the effect of bend-twist coupling is also evaluated. Selecting of an appropriate displacement field for deflection of the composite beam and using the principle of total minimum potential energy, the governing differential equations of motion are obtained and solved using complex infinite Fourier transformation method. The dynamic response of unsymmetric angle-ply laminated beam under moving load has been compared with existing results in the literature and a very good agreement is observed. The results for variation of the deflection, bending moment, shear force and bending stress are presented. In addition, the influences of the stiffness, shear layer viscosity of foundation, velocity of the moving load and also different thicknesses of the beam on the structural response are studied. تفاصيل المقالة -
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39 - Non-linear Static Modeling of Moderately Thick Functionally Graded Plate Using Dynamic Relaxation Method
محمدجواد محمودی وحید محلوجیIn this paper, nonlinear static analysis of moderately thick plate made of functionally graded materials subjected to mechanical transverse loading is carried out using dynamic relaxation method. Mindlin first order shear deformation theory is employed to consider thick أکثرIn this paper, nonlinear static analysis of moderately thick plate made of functionally graded materials subjected to mechanical transverse loading is carried out using dynamic relaxation method. Mindlin first order shear deformation theory is employed to consider thick plate. Discretized equations are extracted for geometrically nonlinear behavior analysis.Loading Conditions and boundary conditions of the plate are uniformly distributed transverse load and simply supported at the four edges of the thick plate, respectively. In order to generalize the obtained results, the equations are solved by applying dynamic relaxation method based on central finite deference discretization in the non-dimensional form. The effects of problem parameters such as gradient constant of the functionally graded material and the side to thickness ratio of plate on the results are investigated. According to the obtained results, the need of including elastic large deflection and applying the theory which considers the effects of plate thickness on the plate bending response and also finally the need of employing dynamic relaxation solution method despite the non-linear terms resulted from large deflection of the functionally graded thick plate are discussed. تفاصيل المقالة -
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40 - Elastic Buckling Analysis of Composite Shells with Elliptical Cross-section under Axial Compression
منصور درویزه ابوالفضل درویزه رضا انصاری الهام کاظمیIn the present research, the elastic buckling of composite cross-ply elliptical cylindrical shells under axial compression is studied through finite element approach. The formulation is based on shear deformation theory and the serendipity quadrilateral eight-node eleme أکثرIn the present research, the elastic buckling of composite cross-ply elliptical cylindrical shells under axial compression is studied through finite element approach. The formulation is based on shear deformation theory and the serendipity quadrilateral eight-node element is used to study the elastic behavior of elliptical cylindrical shells. The strain-displacement relations are accurately accounted for in the formulation in local coordinate system. The contributions of the work done by applied load are also incorporated. The obtained governing equations by the principle of minimum potential energy is solved through eigenvalue approach. The influence of elliptical cross-sectional parameters on the critical buckling loads of elliptical cylindrical shells is examined .Results show that changes in the elliptical cross-sectional parameters significantly change critical buckling loads of the elliptical cylindrical shells. تفاصيل المقالة -
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41 - Bending analysis of composite sandwich plates using generalized differential quadrature method based on FSDT
مصطفی یزدانی اعظم قاسمی محمد هدایتیNowadays, the technology intends to use materials such as magnesium alloys due to their high strength to weight ratio in engine components. As usual, engine cylinder heads and blocks has made of various types of cast irons and aluminum alloys. However, magnesium alloys أکثرNowadays, the technology intends to use materials such as magnesium alloys due to their high strength to weight ratio in engine components. As usual, engine cylinder heads and blocks has made of various types of cast irons and aluminum alloys. However, magnesium alloys has physical and mechanical properties near to aluminum alloys and reduce the weight up to 40 percents. In this article, a new low cycle fatigue lifetime prediction model is presented for a magnesium alloy based on energy approach and to obtain this objective, the results of low cycle fatigue tests on magnesium specimens are used. The presented model has lower material constants in comparison to other criteria and also has proper accuracy; because in energy approaches, a plastic work-lifetime relation is used where the plastic work is the multiple of stress and plastic strain. According to cyclic softening behaviors of magnesium and aluminum alloys, plastic strain energy can be proper selection, because of being constant the product value of stress and plastic strain during fatigue loadings. In addition, the effect of mean stress is applied to the low cycle fatigue lifetime prediction model by using a correction factor. The results of presented models show proper conformation to experimental results تفاصيل المقالة -
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42 - Analysis of Bending and Buckling of Circular Porous Plate Using First-Order Shear Deformation Theory
A.R. Yadegari Naeini Yadegari Naeini A. GhasemiPorous materials are lightweight, flexible and resistant to hairline cracks, so today with the development of technology porous structure produced for use in various industries. This structure widely use in beams, plates and shells. The purpose of this paper is to inves أکثرPorous materials are lightweight, flexible and resistant to hairline cracks, so today with the development of technology porous structure produced for use in various industries. This structure widely use in beams, plates and shells. The purpose of this paper is to investigate the effect of porosity in axial symmetry in bending and buckling load sheet for analysis. For this purpose, a circular plate with simply supported edges under uniform radial pressure and vertical pressure distribution is investigated. Mechanical properties of porous sheet are isotropic and variable in thickness direction is considered. Right movement is extended in accordance with the first order shear deformation theory. Then, using the principle of virtual work and applying the calculus of variations, differential equations, and equations for bending sheet stability are achieved, continue using these equations and Galerkin method, bending and buckling of the sheet is calculated. Buckling load is calculated for all types of porosity can be observed with increasing porosity, critical buckling load decreases. Buckling load is calculated for all types of porosity can be observed with increasing porosity, critical buckling load decreases. The distribution of bending stress and deflection analysis sheet was obtained. To verify the results of bending and buckling of the sheet, the results were compared with homogeneous sheet with classical theory. تفاصيل المقالة
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