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دسترسی آزاد مقاله
1 - اثر ناهمگنی مصنوعی دانسیته بر مدول‌برشی دینامیک چوب بلوط بلند مازو (<i>Quercus castaneifolia</i>)
مصطفی کهن ترابی امیر هومن حمصی محمد طلایی پور مهران روح نیا بهزاد بازیاردر این تحقیق به بررسی تاثیر ایجاد ناهمگنی مصنوعی دانسیته در ناحیه ابتدایی و میانی تیرهای بلوط بلند مازو (Quercus castaneifolia) با بررسی تغییرات حاصل در مدول‌برشی دینامیک حاصل از روش ارتعاش خمشی آزاد در تیر دو سر آزاد پرداخته شده است. بدین منظور تعداد 10 آزمونه از گون چکیده کاملدر این تحقیق به بررسی تاثیر ایجاد ناهمگنی مصنوعی دانسیته در ناحیه ابتدایی و میانی تیرهای بلوط بلند مازو (Quercus castaneifolia) با بررسی تغییرات حاصل در مدول‌برشی دینامیک حاصل از روش ارتعاش خمشی آزاد در تیر دو سر آزاد پرداخته شده است. بدین منظور تعداد 10 آزمونه از گونه بلوط با ابعاد 720× 40× 20 میلی ‎ متر (طولی، شعاعی و مماسی) جهت تعیین مدول‌برشی در تیرهای اولیه مورد آزمون ارتعاش خمشی آزاد در تیر دو سر آزاد قرار گرفتند. پس از آن آزمونه ها به دو گروه تقسیم شده و از گروه اول بلوک هایی به ابعاد 40×40×20 میلی متر از قسمت ابتدایی و از گروه دوم بلوک هایی با ابعاد ذکرشده از قسمت میانی استخراج شده و توسط چسب پلی وینیل استات به یکدیگر متصل شده و پس از برقراری اتصال آزمون ارتعاش خمشی آزاد مجددا بر روی آزمونه ها صورت پذیرفت. پس از آن بلوک های بلوط از محل اتصال خارج شده و در دو مرحله بلوک‌هایی از دو گونه صنوبر (Populus nigra) و انجیلی (Parrotia persica) در آنها جایگزاری شده و به‌منظور تاثیر ناهمگنی ایجاد شده توسط هر یک از بلوک های جایگزین شده بر مقادیر مدول‌برشی، آزمون ارتعاش خمشی بر روی آنها صورت پذیرفت. نتایج حاکی از آن بود که ایجاد ناهمگنی مصنوعی دانسیته در ناحیه ابتدایی تیر توسط هر سه گونه بلوط، صنوبر و انجیلی تاثیر معنی داری بر مقادیر مدول برشی دینامیک ندارد، درحالی‌که ایجاد ناهمگنی در قسمت میانی تیر باعث افت معنی دار مقادیر حاصل از این فاکتور شده است. تیرهای ناهمگن شده توسط گونه انجیلی بیشترین و تیرهای ناهمگن شده توسط گونه بلوط با کمترین درصد افت در مقادیر مدول برشی دینامیک مواجه شدند. پرونده مقاله -
دسترسی آزاد مقاله
2 - Free Vibration Analysis of Nanoplates using Differential Transformation Method
Sayed Hassan Nourbakhsh Mohsen Botshekanan Dehkordi Amir AtrianIn this paper, a free vibration of nano-plates is investigated considering the small scale parameter. The used rectangular nano plate is thin and under different boundary conditions. In order to obtain the natural frequencies of the nano-plates, classical plate theory o چکیده کاملIn this paper, a free vibration of nano-plates is investigated considering the small scale parameter. The used rectangular nano plate is thin and under different boundary conditions. In order to obtain the natural frequencies of the nano-plates, classical plate theory on the basis of non-local theory is used. The governing equation is solved using a semi-analytical method DTM[1]. The results for free vibration of those plates are compared with the theoretical data published in the literature. Results show that DTM is a powerful, simple, accurate and fast method for solving equations in comparison with other methods. Non-local parameter is very effective in vibration of nano-plates and its influence is different in various boundary conditions. Influence of this parameter in simply supported-clamp boundary condition is higher than other boundary conditions. پرونده مقاله -
دسترسی آزاد مقاله
3 - A Surrogate Reduced Order Free Vibration Model of Linear and Non-Linear Beams using Modified Modal Coefficients and HOSVD Approaches
Mohammad Kazem MoayyediIn the present work, two low-dimensional models are presented and used for vibration simulation of the linear and non-linear beam models. These models help to compute the dynamical responses of the beam with fast computation speed and under the effects of different cond چکیده کاملIn the present work, two low-dimensional models are presented and used for vibration simulation of the linear and non-linear beam models. These models help to compute the dynamical responses of the beam with fast computation speed and under the effects of different conditions. Also the obtained results can be used in the conceptual and detailed design stages of an engineering system overall design. First, a finite element analysis based on Euler-Bernoulli beam elements with two primary variables (deflection and slope) at each node is used to find static and dynamic responses of the considered linear and non-linear beams. Responses to three different static load cases are obtained and applying them as initial conditions, the time responses of the beam are calculated by the Newmark's time approximation scheme. A low-dimensional POD model which was extracted from the ensemble under the effect of an arbitrary loading is reconstructed. To apply the model to simulate the response of beam under the effect of other loads, POD modal coefficients are updated due to change of initial condition. This modification is performed based on the recalculation of the eigenvalues due to a new initial condition. Also, another low-dimensional model is constructed which is developed based on an ensemble under the effect of several parameters. To apply the model to simulate the response of the beam under the effect of other loads and variations of beam thickness, POD-HOSVD modal coefficients are updated due to the change of desired parameters. The results obtained from the low-dimensional model are showing good agreement to the benchmark data and proving high level accuracy of the model. پرونده مقاله -
دسترسی آزاد مقاله
4 - Effect of Important Physical and Geometrical Parameters on the Dynamic Response of Thick Composite Plates with Smart Attached Mass
Ali Pourmoayed keramat Malekzadeh Fard naser zolghadrIn this research, the effect of different structural parameters on the dynamic behaviour of a thick plate with a smart attached mass, which is a mass embedded with the Shape Memory Alloy (SMA) fibers were investigated. The results showed that the inherent stiffness of t چکیده کاملIn this research, the effect of different structural parameters on the dynamic behaviour of a thick plate with a smart attached mass, which is a mass embedded with the Shape Memory Alloy (SMA) fibers were investigated. The results showed that the inherent stiffness of the smart attached mass and the localized stiffness due to the effect of SMA fibers both play a significant role in the dynamic behaviour of the plate, and ignoring either of these parameters results in a considerable change in the system responses. The size and position of the smart attached mass were also found to be of particular importance, since the effect of the weight of SMA and attached mass and the forces induced by SMA transformation all have significant and sometimes conflicting effects on the system vibrations. The results also showed that the changes in the system parameters, and particularly the characteristics of the SMA fibers such as activation temperature, pre-strain, and volume fraction, result in the appearance of dynamic responses that cannot be neglected. پرونده مقاله -
دسترسی آزاد مقاله
5 - 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 چکیده کاملThis 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. پرونده مقاله -
دسترسی آزاد مقاله
6 - Free Vibration of Defective Nanographene using Molecular Dynamics Simulation and Differential Quadrature Method
Hossein Golestanian ali khodadadi mahmoud haghighiIn this paper, the free vibration of defective nanographene is investigated using Molecular Dynamics Simulation (MD) and Differential Quadrature Method (DQM). The equations of motions and the related boundary conditions are derived based on the differential constitutive چکیده کاملIn this paper, the free vibration of defective nanographene is investigated using Molecular Dynamics Simulation (MD) and Differential Quadrature Method (DQM). The equations of motions and the related boundary conditions are derived based on the differential constitutive relations in conjunction with the classical plate theory via Hamilton’s principle. Then, DQM is used to investigate free vibration of the nanographene with various boundary conditions. At first, in order to determine natural frequencies more realistically, nanographene mechanical properties are determined using MD simulations. The effects of defects are investigated by analyzing pristine and defective nanographenes containing Stone Wales, vacancy, and Adatom defects. According to the results, the non-dimensional fundamental natural frequency parameter converges to the analytical value for N=10×10. Results indicate that graphene with CCCC boundary conditions has the maximum natural frequency. The minimum value corresponds to the graphene with SSSS boundary conditions. In addition, Non-dimensional fundamental frequency parameter of the nanoplate increases with increasing nanoplate aspect ratio. Finally, defects reduce density, position ratio and elastic moduli of nanographene, which causes a decrease in natural frequency. Stone Wales and vacancy defects decrease nanographene natural frequencies by about 8 and 25 percent, respectively. پرونده مقاله -
دسترسی آزاد مقاله
7 - Frequency Analysis of Ring-Stiffened Composite Cylindrical Shell using Experimental, Analytical and Finite Element Methods
Hadi Salimi Ali Davar Mohsen Heydari Beni Jafar Eskandari Jam Majid Eskandari ShahrakiIn this paper, free vibration of laminated composite cylindrical shells reinforced with circumferential rings, are investigated with experimental, analytical and finite element methods and natural frequencies are obtained. The analysis is carried out for clamp-free and چکیده کاملIn this paper, free vibration of laminated composite cylindrical shells reinforced with circumferential rings, are investigated with experimental, analytical and finite element methods and natural frequencies are obtained. The analysis is carried out for clamp-free and clamp-clamp boundary conditions and the results are compared with each other. To solve the problem, the equilibrium Equations of motions are written according to the classical shells theory and after simplification, the structural stiffness and mass matrices and the frequency Equation are derived using Galerkin method. The results obtained in this paper, are compared with the results available in the literatures, and the results of experimental and finite element methods and good agreement is observed. پرونده مقاله -
دسترسی آزاد مقاله
8 - Vibration Analysis of Rotating Disk Carrying Annular Concentrated Masses in Turbo-pump System
Behrooz Shahriari Mostafa Nazemizadeh A. M. ShirvaniVibration analysis of rotating disks is one of the most important problems in turbomachines. In this study, a new method has been presented which analyzed the radial vibration of a turbo-pump rotating disk carrying two annular concentrated masses located on the disk and چکیده کاملVibration analysis of rotating disks is one of the most important problems in turbomachines. In this study, a new method has been presented which analyzed the radial vibration of a turbo-pump rotating disk carrying two annular concentrated masses located on the disk and at its end. Natural frequencies have been calculated in different rotating speeds; then results have been compared with each other. The effects of concentrated masses position and intensity on natural frequencies have been investigated. The results show that concentrated masses always have been decreased the value of first natural frequency, but in the case of second and third natural frequencies, depending on the mass concentration magnitude and its position, the magnitude of natural frequency has been increased or decreased. The vibration of the rotating disk without considering the concentrated mass, was examined. Then the resulting solution was generalized for two connected disks in internal concentrated mass location. The effect of concentrated masses, one on the disk body and the other on the outside of the disk, is considered as boundary conditions in the two disk Equations. The results show that increasing in angular velocity of rotating disk reduces the natural frequency. Concentrated masses always reduce the first natural frequency. At the second and third natural frequencies, concentrated masses may increase or decrease the natural frequency, which depends on the value and position of concentrated mass. Concentrated mass has the most impact when it is in a position that has the most radial displacement. پرونده مقاله -
دسترسی آزاد مقاله
9 - A Plate Bending Kirchhoff Element Based on Assumed Strain Functions
F Boussem L BelounarTo investigate static and free vibration for thin plate bending structures, a four-node quadrilateral finite element is proposed in this research paper. This element has been formulated by using both the assumptions of thin plates theory (Kirchhoff plate theory) and str چکیده کاملTo investigate static and free vibration for thin plate bending structures, a four-node quadrilateral finite element is proposed in this research paper. This element has been formulated by using both the assumptions of thin plates theory (Kirchhoff plate theory) and strain approach. The suggested element which possesses only three degrees of freedom (one transverse displacement and two normal rotations) at each of four corner nodes is based on assumed higher-order functions for the various components of strain field that satisfies the compatibility equation. The displacement functions of the developed element are obtained by integrating the assumed strains functions and satisfy the exact representation of the rigid body modes. Several numerical tests in both static and free vibration analysis are presented to assess the performance of the new element. The obtained results show high solution accuracy, especially for coarse meshes, of the developed element compared with analytical and other numerical solutions available in the literature. پرونده مقاله -
دسترسی آزاد مقاله
10 - Free Vibration Analysis of Nonlinear Circular Plates Resting on Winkler and Pasternak Foundations
M.G Sobamowo S.A SalawuDynamic behaviour of nonlinear free vibration of circular plate resting on two-parameters foundation is studied. The governing ordinary differential equation is solved analytically using hybrid Laplace Adomian decomposition method. The analytical solutions obtained are چکیده کاملDynamic behaviour of nonlinear free vibration of circular plate resting on two-parameters foundation is studied. The governing ordinary differential equation is solved analytically using hybrid Laplace Adomian decomposition method. The analytical solutions obtained are verified with existing results in literature. The analytical solutions are used to determine the influence of elastic foundation, radial and circumferential stress on natural frequency of the plate. Also, the radial and circumferential stress determined. From the results, it is observed that, increase in elastic foundation parameter increases the natural frequency of the plate. It is recorded that the modal radial and circumferential stress affect the extrema mode of the plate. It is hoped that the present study will contribute to the existing knowledge in the field of vibration analysis of engineering structures. پرونده مقاله -
دسترسی آزاد مقاله
11 - Experimental and Numerical Free Vibration Analysis of Hybrid Stiffened Fiber Metal Laminated Circular Cylindrical Shell
A Nazari K Malekzadeh A.A NaderiThe modal testing has proven to be an effective and non-destructive test method for estimation of the dynamic stiffness and damping constant. The aim of the present paper is to investigate the modal response of stiffened Fiber Metal Laminated (FML) circular cylindrical چکیده کاملThe modal testing has proven to be an effective and non-destructive test method for estimation of the dynamic stiffness and damping constant. The aim of the present paper is to investigate the modal response of stiffened Fiber Metal Laminated (FML) circular cylindrical shells using experimental and numerical techniques. For this purpose, three types of FML-stiffened shells are fabricated by a specially-designed method and the burning examination is used to determine the mechanical properties of them. Then, modal tests are conducted to investigate the vibration and damping characteristics of the FML-stiffened shells. A 3D finite element model is built using ABAQUS software to predict the modal characteristics of the FML-stiffened circular cylindrical shells with free-free ends. Finally, the achievements from the numerical and experimental analyses are compared with each other and good agreement has been obtained. Modal analyses of the FML-stiffened circular cylindrical shells are investigated for the first time in this paper. Thus, the results obtained from this study are novel and can be used as a benchmark for further studies. پرونده مقاله -
دسترسی آزاد مقاله
12 - Free Vibration Analysis of Functionally Graded Piezoelectric Material Beam by a Modified Mesh Free Method
M Foroutan Sh Sharafi S MohammadiA mesh-free method based on moving least squares approximation (MLS) and weak form of governing equations including two dimensional equations of motion and Maxwell’s equation is used to analyze the free vibration of functionally graded piezoelectric material (FGPM چکیده کاملA mesh-free method based on moving least squares approximation (MLS) and weak form of governing equations including two dimensional equations of motion and Maxwell’s equation is used to analyze the free vibration of functionally graded piezoelectric material (FGPM) beams. Material properties in beam are determined using a power law distribution. Essential boundary conditions are imposed by the transformation method. The mesh-free method is verified by comparison with a finite element method (FEM) which performed for FGPM beams. Comparisons showed that this model has a good accuracy. After validation of the presented model, a parametric study was carried out to investigate the effect of mechanical and electrical boundary conditions, slenderness ratio and distribution of constituent materials on natural frequencies of FGPM beams. It is concluded that slenderness ratio has more significant effect on lower frequencies. On the other hand higher frequencies are affected by the volume fraction power index much more than lower frequencies. پرونده مقاله -
دسترسی آزاد مقاله
13 - 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 چکیده کاملThis 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. پرونده مقاله -
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14 - Size-Dependent Vibration Problem of Two Vertically-Aligned Single-Walled Boron Nitride Nanotubes Conveying Fluid in Thermal Environment Via Nonlocal Strain Gradient Shell Model
P Roodgar Saffari M Fakhraie M. A RoudbariThe free vibration behavior of two fluid-conveying vertically-aligned single-walled boron nitride nanotubes are studied in the present paper via the nonlocal strain gradient piezoelectric theory in conjunction with the first-order shear deformation shell assumption in t چکیده کاملThe free vibration behavior of two fluid-conveying vertically-aligned single-walled boron nitride nanotubes are studied in the present paper via the nonlocal strain gradient piezoelectric theory in conjunction with the first-order shear deformation shell assumption in thermal environments. It is supposed that the two adjacent boron nitride nanotubes are coupled with each other in the context of linear deformation by van der Waals interaction according to Lennard–Jones potential function. To achieve a more accurate modeling for low-scale structures, both hardening and softening effects of materials are considered in the nonlocal strain gradient approach. Themotion equations and associated boundary conditions are derived by means of Hamilton’s variational principle, then solved utilizing differential quadrature method. Numerical studies are done to reveal the effect of different boundary conditions, size scale parameters, aspect ratio, inter-tube distance, and temperature change on the variations of dimensionless eigenfrequency and critical flow velocity. پرونده مقاله -
دسترسی آزاد مقاله
15 - Vibration Behavior of Thick Sandwich Composite Beam with Flexible Core Resting on Incompressible Fluid Foundation
M Khosravi S Jafari Mehrabadi K Malekzadeh FardIn this research, free flexural vibration of a thick sandwich composite beam that is made up of two composite face sheets and a flexible foam-made core based on a fluid is investigated. Governing equations for the sandwich beam were extracted using a higher-order theory چکیده کاملIn this research, free flexural vibration of a thick sandwich composite beam that is made up of two composite face sheets and a flexible foam-made core based on a fluid is investigated. Governing equations for the sandwich beam were extracted using a higher-order theory. The face sheets were modeled using the first-order shear deformation theory (FSDT). In the analysis of the multilayer sandwich composite beam, the layers and the core in the middle were assumed to be well attached to one another, and continuous strain functions at the layer interfaces were assumed. Moreover, displacements were assumed to be small, so that the analyses could be performed in linear elastic region with simply supported boundary condition for the beam. Equations of motion of the beam were extracted using energy equations and Hamilton’s principle. Continuing with the research, effects of changing different parameters were evaluated; these included core thickness to total thickness ratio, beam length to total thickness ration, face sheet material, fluid density, and fluid height. The results showed that the presence of the liquid tend to lower the natural frequency of the structure. Our investigations further indicated that the natural frequency follows an increasing trend with decreasing the fluid density. پرونده مقاله -
دسترسی آزاد مقاله
16 - Free Vibration Analysis of Composite Grid Stiffened Cylindrical Shells Using A Generalized Higher Order Theory
H Mohammad Panahiha A Davar M Heydari Beni J Eskandari JamThe present study analyzes the free vibration of multi-layered composite cylindrical shells and perforated composite cylindrical shells via a modified version of Reddy’s third-order shear deformation theory (TSDT) under simple support conditions. An advantage of t چکیده کاملThe present study analyzes the free vibration of multi-layered composite cylindrical shells and perforated composite cylindrical shells via a modified version of Reddy’s third-order shear deformation theory (TSDT) under simple support conditions. An advantage of the proposed theory over other high-order theories is the inclusion of the shell section trapezoidal form coefficient term in the displacement field and strain equations to improve the accuracy of results. The non-uniform stiffness and mass distributions across reinforcement ribs and the empty or filled bays between the ribs in perforated shells were addressed via a proper distribution function. For integrated perforated cylindrical shells, the results were validated by comparison to other studies and the numerical results obtained via ABAQUS. The proposed theory was in good consistency with numerical results and the results of previous studies. It should be noted that the proposed theory was more accurate than TSDT. پرونده مقاله -
دسترسی آزاد مقاله
17 - On The Free Vibration of Doubly Clamped Single-Walled Coiled Carbon Nanotubes: A Novel Size Dependent Continuum Model
F Darvishi O RahmaniIn this paper, the size dependent vibration behavior of doubly clamped single-walled coiled carbon nanotubes (CCNTs) is investigated using nonlocal helical beam model. This model is based on Washizu’s beam theory so that all displacement components of CCNT in the چکیده کاملIn this paper, the size dependent vibration behavior of doubly clamped single-walled coiled carbon nanotubes (CCNTs) is investigated using nonlocal helical beam model. This model is based on Washizu’s beam theory so that all displacement components of CCNT in the equations of motion are defined at the centroidal principal axis and transverse shear deformations are considered. After deriving the nonlocal free vibration equations, they are solved by the generalized differential quadrature method (GDQM). Then, the natural frequencies and corresponding mode shapes are determined for the clamped-clamped boundary conditions (BCs). After that, a parametric study on the effect of different parameters, including the helix cylinder to the tube diameters ratio , the number of pitches, the helix pitch angle, and the nonlocal parameter on the natural frequencies is conducted. It is worth noting that the results of the proposed method would be useful in the practical applications of CCNTs such as using in nanoelectromechanical systems. پرونده مقاله -
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18 - Magneto-Rheological Response in Vibration of Intelligent Sandwich Plate with Velocity Feedback Control
A Mihankhah Z Khoddami Maraghi A Ghorbanpour Arani S NiknejadThis study deals with the free vibration of the sandwich plate made of two smart magnetostrictive face sheets and an electro-rheological fluid core. Electro-rheological fluids are polymer-based material that changes its viscosity under the applied electric field. A feed چکیده کاملThis study deals with the free vibration of the sandwich plate made of two smart magnetostrictive face sheets and an electro-rheological fluid core. Electro-rheological fluids are polymer-based material that changes its viscosity under the applied electric field. A feedback control system follows the magnetization effect on the vibration characteristics of the sandwich plate when subjected to the magnetic field. It is assumed that there is no slip between layers, so the stress-strain relations of each layer are separately considered. Energy method is utilized in order to derive the five coupled equations of motion. These equations are solved by differential quadrature method (DQM). Results of this study show the rheology response of fluid in presence of electric field where the core gets hard and the dimensionless frequency increases. Also, the significant effect of thickness and aspect ratios and velocity feedback gain are discussed in detail. Such intelligent structures can replace in many of the systems used in automotive, aerospace and building industries as the detector, warning, and vibration absorber etc. پرونده مقاله -
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19 - Free Vibration Analysis of Bidirectional Functionally Graded Conical/Cylindrical Shells and Annular Plates on Nonlinear Elastic Foundations, Based on a Unified Differential Transform Analytical Formulation
M Molla-Alipour M Shariyat M ShabanIn the present research, a unified formulation for free vibration analysis of the bidirectional functionally graded conical and cylindrical shells and annular plates on elastic foundations is developed. To cover more individual cases and optimally tailored material prop چکیده کاملIn the present research, a unified formulation for free vibration analysis of the bidirectional functionally graded conical and cylindrical shells and annular plates on elastic foundations is developed. To cover more individual cases and optimally tailored material properties, the material properties are assumed to vary in both the meridian/radial and transverse directions. The shell/plate is assumed to be supported by a non-uniform Winkler-type elastic foundation in addition to the edge constraints. Therefore, the considered problem contains some complexities that have not been considered together in the available researches. The proposed unified formulation is derived based on the principle of minimum total potential energy and solved using a differential transform analytical method whose center is located at the outer edge of the shell or plate; so that the resulting semi-analytical solution can be employed not only for truncated conical shells and annular plates, but also for complete conical shells and circular plates. Accuracy of results of the proposed unified formulation is verified by comparing the results with those of the three-dimensional theory of elasticity extracted from the ABAQUS finite element analysis code. A variety of the edge condition combinations are considered in the results section. A comprehensive parametric study including assessment of influences of the material properties indices, thickness to radius ratio, stiffness distribution of the elastic foundation, and various boundary conditions, is accomplished. Results reveal that influence of the meridian variations of the material properties on the natural frequencies is more remarkable than that of the transverse gradation. پرونده مقاله -
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20 - Considering Bending and Vibration of Homogeneous Nanobeam Coated by a FG Layer
H Salehipour M Jamshidi A ShahsavarIn this research static deflection and free vibration of homogeneous nanobeams coated by a functionally graded (FG) layer is investigated according to the nonlocal elasticity theory. A higher order beam theory is used that does not need the shear correction factor. The چکیده کاملIn this research static deflection and free vibration of homogeneous nanobeams coated by a functionally graded (FG) layer is investigated according to the nonlocal elasticity theory. A higher order beam theory is used that does not need the shear correction factor. The equations of motion (equilibrium equations) are extracted by using Hamilton’s principle. The material properties are considered to vary in the thickness direction of FG coated layer. This nonlocal nanobeam model incorporates the length scale parameter (nonlocal parameter) that can capture the small scale effects. In the numerical results section, the effects of different parameters, especially the ratio of thickness of FG layer to the total thickness of the beam are considered and discussed. The results reveal that the frequency is maximum for a special value of material power index. Also, increasing the ratio of thickness of FG layer to the total thickness of the beam increases the static deflection and decreases the natural frequencies. These results help with the understanding such coated structures and designing them carefully. The results also show that the new nonlocal FG nanobeam model produces larger vibration and smaller deflection than homogeneous nonlocal nanobeam. پرونده مقاله -
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21 - An Analytical Solution on Size Dependent Longitudinal Dynamic Response of SWCNT Under Axial Moving Harmonic Load
F Khosravi M Simyari S. A Hosseini M GhadiriThe main purposes of the present work are devoted to the investigation of the free axial vibration, as well as the time-dependent and forced axial vibration of a SWCNT subjected to a moving load. The governing equation is derived through using Hamilton's principle. Erin چکیده کاملThe main purposes of the present work are devoted to the investigation of the free axial vibration, as well as the time-dependent and forced axial vibration of a SWCNT subjected to a moving load. The governing equation is derived through using Hamilton's principle. Eringen’s nonlocal elasticity theory has been utilized to analyze the nonlocal behaviors of SWCNT. A Galerkin method based on a closed-form solution is applied to solve the governing equation. The boundary conditions are considered as clamped-clamped (C-C) and clamped-free (C-F). Firstly, the nondimensional natural frequencies are calculated, as well as the influence of the nonlocal parameter on them are explained. The results of both boundary conditions are compared together, and both of them are compared to the results of another study to verify the accuracy and efficiency of the present results. The novelty of this work is related to the study of the dynamic forced axial vibration due to the axial moving harmonic force in the time domain. The previously forced vibration studies were devoted to the transverse vibrations. The effect of the geometrical parameters, velocity of the moving load, excitation frequency, as well as the small-scale effect, are explained and discussed in this context. According to the lack of accomplished studies in this field, the present work has the potential to be used as a benchmark for future works. پرونده مقاله -
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22 - Size-Dependent Higher Order Thermo-Mechanical Vibration Analysis of Two Directional Functionally Graded Material Nanobeam
M Mahinzare S Amanpanah M GhadiriThis paper represented a numerical technique for discovering the vibrational behavior of a two-directional FGM (2-FGM) nanobeam exposed to thermal load for the first time. Mechanical attributes of two-directional FGM (2-FGM) nanobeam are changed along the thickness and چکیده کاملThis paper represented a numerical technique for discovering the vibrational behavior of a two-directional FGM (2-FGM) nanobeam exposed to thermal load for the first time. Mechanical attributes of two-directional FGM (2-FGM) nanobeam are changed along the thickness and length directions of nanobeam. The nonlocal Eringen parameter is taken into the nonlocal elasticity theory (NET). Uniform temperature rise (UTR), linear temperature rise (LTR), non-linear temperature rise (NLTR) and sinusoidal temperature rise (STR) during the thickness and length directions of nanobeam is analyzed. Third-order shear deformation theory (TSDT) is used to derive the governing equations of motion and associated boundary conditions of the two-directional FGM (2-FGM) nanobeam via Hamilton’s principle. The differential quadrature method (DQM) is employed to achieve the natural frequency of two-directional FGM (2-FGM) nanobeam. A parametric study is led to assess the efficacy of coefficients of two-directional FGM (2-FGM), Nonlocal parameter, FG power index, temperature changes, thermal rises loading and temperature rises on the non-dimensional natural frequencies of two-directional FGM (2-FGM) nanobeam. پرونده مقاله -
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23 - Nonlinear Free Vibration Analysis of Functionally Graded Sandwich Beam with Magnetorheological Fluid Core Using Timoshenko Beam Theory
O Miraliyari S Jafari Mehrabadi M.M NajafizadehIn this paper, the analysis of nonlinear free vibrations of beams made of functionally graded materials with magnetorheological fluid as core is investigated. It is assumed that the beam is made of three layers including constraining layer, magnetorheological fluid and چکیده کاملIn this paper, the analysis of nonlinear free vibrations of beams made of functionally graded materials with magnetorheological fluid as core is investigated. It is assumed that the beam is made of three layers including constraining layer, magnetorheological fluid and base layer and is located on Simply-Simply, Clamped-Simply and Clamped–Clamped supports. The governing equations of the beam are derived using the Hamilton’s principle. To obtain the vibrational frequencies, the theory of Timoshenko beam is used by the Generalized Differential Quadrature method. The effects of magnetic field intensity, power law exponents, core thickness and constraining layer thickness and the length of the beam on natural frequency and modal loss factor related to different frequencies modes for the three boundary conditions have been investigated. The results show the effects of physical and geometrical parameters regarding the natural frequency and modal loss factor of the sandwich beam with different modes. Also, the frequency and loss factor values obtained from Generalized Differential Quadrature method are very close to the results obtained by the Finite Element method. This shows the accuracy and precision of this method. پرونده مقاله -
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24 - 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 چکیده کاملIn 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. پرونده مقاله -
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25 - 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 چکیده کاملIn 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. پرونده مقاله -
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26 - Buckling and Free Vibrations of a Magneto-Electro-Elastic Sandwich Panel with Flexible Core
H Talebi Amanieh S.A Seyed Roknizadeh A RezaThis paper presents the buckling and out-of-plane free vibration response of a sandwich panel with flexible core for the different boundary condition. In the desired configuration of the sandwich panel, the top and bottom plates are made of magneto-electro-elastic (MEE) چکیده کاملThis paper presents the buckling and out-of-plane free vibration response of a sandwich panel with flexible core for the different boundary condition. In the desired configuration of the sandwich panel, the top and bottom plates are made of magneto-electro-elastic (MEE) plates. Moreover, the in-plane electric and magnetic potential fields are neglected for the derivation of the required relations. The sandwich structure is subjected to axial force in both longitudinal and transverse directions; in addition, and the top and bottom plates are exposed to electric and magnetic fields. The governing equations of motion for MEE sandwich panel with a flexible core are derived based on the first-order shear deformation theory by neglecting the displacement of the mid-plate and using the Hamilton’s principle. Furthermore, the derived partial differential equations (PDEs) are solved. According to the obtained numerical results, the core thickness, variation of electric field, variation of magnetic field and plate length are introduced as the most influential parameters on the free vibration response of the panel as well as the critical force of buckling. As one of the results, the electric potential is inversely related to the natural frequency and buckling load, so that with increasing the electric potential, the natural frequency and critical load of the structure is also increased.Moreover, the magnetic potential is directly related to the natural frequency and buckling load of the system, and increasing trends of natural frequency and critical load are observed by increasing the magnetic potential. پرونده مقاله -
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27 - Free Vibration of Sandwich Panels with Smart Magneto-Rheological Layers and Flexible Cores
G Payganeh K Malekzadeh H Malek-MohammadiThis is the first study on the free vibrational behavior of sandwich panels with flexible core in the presence of smart sheets of oil which is capable of the excitation of magnetic field. In order to model the core, the improved high order theory of sandwich sheets was چکیده کاملThis is the first study on the free vibrational behavior of sandwich panels with flexible core in the presence of smart sheets of oil which is capable of the excitation of magnetic field. In order to model the core, the improved high order theory of sandwich sheets was used by a polynomial with unknown coefficients first degree shear theory was used for the sheets. The derived equations based on Hamilton principle with simple support boundary condition for upper and lower sheets were solved using Navier technique. Accuracy and precision of the theory were investigated by comparing the results of this study with those of analytical and numerical works. In the conclusion section, effect of the intensity of magnetic field and other physical parameters including ratio of sheet's length to width, ratio of sheet's length to thickness, ratio of core thickness to sheet's overall thickness, and ratio of oil layer thickness to sheet's overall thickness on natural frequency was investigated. پرونده مقاله -
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28 - Free Vibration of Functionally Graded Beams with Piezoelectric Layers Subjected to Axial Load
M Karami KhorramabadiThis paper studies free vibration of simply supported functionally graded beams with piezoelectric layers subjected to axial compressive loads. The Young's modulus of beam is assumed to be graded continuously across the beam thickness. Applying the Hamilton’s prin چکیده کاملThis paper studies free vibration of simply supported functionally graded beams with piezoelectric layers subjected to axial compressive loads. The Young's modulus of beam is assumed to be graded continuously across the beam thickness. Applying the Hamilton’s principle, the governing equation is established. Resulting equation is solved using the Euler’s Equation. The effects of the constituent volume fractions, the influences of applied voltage and axial compressive loads on the vibration frequency are presented. To investigate the accuracy of the present analysis, a compression study is carried out with a known data. پرونده مقاله -
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29 - A Nonlocal First Order Shear Deformation Theory for Vibration Analysis of Size Dependent Functionally Graded Nano beam with Attached Tip Mass: an Exact Solution
M Ghadiri A JafariIn this article, transverse vibration of a cantilever nano- beam with functionally graded materials and carrying a concentrated mass at the free end is studied. Material properties of FG beam are supposed to vary through thickness direction of the constituents according چکیده کاملIn this article, transverse vibration of a cantilever nano- beam with functionally graded materials and carrying a concentrated mass at the free end is studied. Material properties of FG beam are supposed to vary through thickness direction of the constituents according to power-law distribution (P-FGM). The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived based on Timoshenko beam theory in order to consider the effect of shear deformation and rotary inertia. Hamilton’s principle is applied to obtain the governing differential equation of motion and boundary conditions and they are solved applying analytical solution. The purpose is to study the effects of parameters such as tip mass, small scale, beam thickness, power-law exponent and slenderness on the natural frequencies of FG cantilever nano beam with a point mass at the free end. It is explicitly shown that the vibration behavior of a FG Nano beam is significantly influenced by these effects. The response of Timoshenko Nano beams obtained using an exact solution in a special case is compared with those obtained in the literature and is found to be in good agreement. Numerical results are presented to serve as benchmarks for future analyses of FGM cantilever Nano beams with tip mass. پرونده مقاله -
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30 - Free Vibration Analysis of a Nonlinear Beam Using Homotopy and Modified Lindstedt-Poincare Methods
M.T Ahmadian M Mojahedi H MoeenfardIn this paper, homotopy perturbation and modified Lindstedt-Poincare methods are employed for nonlinear free vibrational analysis of simply supported and double-clamped beams subjected to axial loads. Mid-plane stretching effect has also been accounted in the model. Gal چکیده کاملIn this paper, homotopy perturbation and modified Lindstedt-Poincare methods are employed for nonlinear free vibrational analysis of simply supported and double-clamped beams subjected to axial loads. Mid-plane stretching effect has also been accounted in the model. Galerkin's decomposition technique is implemented to convert the dimensionless equation of the motion to nonlinear ordinary differential equation. Homotopy and modified Lindstedt-Poincare (HPM) are applied to find analytic expressions for nonlinear natural frequencies of the beams. Effects of design parameters such as axial load and slenderness ratio are investigated. The analytic expressions are valid for a wide range of vibration amplitudes. Comparing the semi-analytic solutions with numerical results, presented in the literature, indicates good agreement. The results signify the fact that HPM is a powerful tool for analyzing dynamic and vibrational behavior of structures analytically. پرونده مقاله -
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31 - Free Vibration and Buckling Analysis of Sandwich Panels with Flexible Cores Using an Improved Higher Order Theory
K Malekzadeh Fard H Malek-MohammadiIn this paper, the behavior of free vibrations and buckling of the sandwich panel with a flexible core was investigated using a new improved ‎high-order sandwich panel theory. In this theory, equations of motion were formulated based on shear stresses in the core. F چکیده کاملIn this paper, the behavior of free vibrations and buckling of the sandwich panel with a flexible core was investigated using a new improved ‎high-order sandwich panel theory. In this theory, equations of motion were formulated based on shear stresses in the core. First-order shear deformation theory was ‎applied for the procedures. In this theory, for the first time, incompatibility problem of velocity and acceleration field existing in Frostig's ‎first theory was solved using a simple analytical method. The main advantage of this theory is its simplicity and less number of equations than the ‎second method of Frostig's high-order theory. To extract dynamic equations of the core, three-dimensional elasticity theory was utilized. ‎Also, to extract the dynamic equations governing the whole system, Hamilton's principle was used. In the analysis of free vibrations, the ‎panel underwent primary pressure plate forces. Results demonstrated that, as plate pre-loads got closer to the critical buckling loads, the natural frequency of the panel tended zero. The results obtained from the present theory were in good correspondence with the ‎results of the most recent papers. پرونده مقاله -
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32 - A Semi-Analytical Solution for Free Vibration and Modal Stress Analyses of Circular Plates Resting on Two-Parameter Elastic Foundations
M.M Alipour M Shariyat M ShabanIn the present research, free vibration and modal stress analyses of thin circular plates with arbitrary edge conditions, resting on two-parameter elastic foundations are investigated. Both Pasternak and Winkler parameters are adopted to model the elastic foundation. Th چکیده کاملIn the present research, free vibration and modal stress analyses of thin circular plates with arbitrary edge conditions, resting on two-parameter elastic foundations are investigated. Both Pasternak and Winkler parameters are adopted to model the elastic foundation. The differential transform method (DTM) is used to solve the eigenvalue equation yielding the natural frequencies and mode shapes of the circular plates. Accuracy of obtained results is evaluated by comparing the results with those available in the well-known references. Furthermore, effects of the foundation stiffness parameters and the edge conditions on the natural frequencies, mode shapes, and distribution of the maximum in-plane modal stresses are investigated. پرونده مقاله -
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33 - Free Vibration Analysis of Orthotropic FGM Cylinders by a Mesh-Free Method
R Moradi-Dastjerdi M ForoutanIn this paper, free vibration analysis of orthotropic functionally graded material (FGM) cylinders was carried out by a Mesh-Free method. In this analysis, moving least squares shape functions are used for approximation of displacement field in the weak form of equilibr چکیده کاملIn this paper, free vibration analysis of orthotropic functionally graded material (FGM) cylinders was carried out by a Mesh-Free method. In this analysis, moving least squares shape functions are used for approximation of displacement field in the weak form of equilibrium equation. Essential boundary conditions are imposed by transformation method. In this simulation, an axisymmetric model is used. The orthotropic FGM cylinders are assumed to be a mixture of two isotropic materials as fiber and matrix. The volume fraction of the fiber is changed in the radial direction. Consequently, mechanical properties of these cylinders are changed in the radial direction. Free vibration analysis of orthotropic FGM cylinders with any arbitrary combination of boundary conditions is possible by the proposed model. Natural frequencies obtained from the presented model are in good agreement with results of finite element simulation and other results from literature. Effects of various types of boundary conditions, geometrical parameters, and mechanical properties on the natural frequencies are studied. پرونده مقاله -
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34 - Free Vibrations of Continuous Grading Fiber Orientation Beams on Variable Elastic Foundations
S Kamarian M.H Yas A PourasgharFree vibration characteristics of continuous grading fiber orientation (CGFO) beams resting on variable Winkler and two-parameter elastic foundations have been studied. The beam is under different boundary conditions and assumed to have arbitrary variations of fiber ori چکیده کاملFree vibration characteristics of continuous grading fiber orientation (CGFO) beams resting on variable Winkler and two-parameter elastic foundations have been studied. The beam is under different boundary conditions and assumed to have arbitrary variations of fiber orientation in the thickness direction. The governing differential equations for beam vibration are being solved using Generalized Differential Quadrature (GDQ) method. Numerical results are presented for a beam with arbitrary variation of fiber orientation in the beam thickness and compared with similar discrete laminate beam. The main contribution of this work is to present useful results for continuous grading of fiber orientation through thickness of a beam on variable elastic foundation and its comparison with similar discrete laminate composite beam. The results show the type of elastic foundation plays very important role on the natural frequency parameter of a CGFO beam. According to the numerical results, frequency characteristics of the CGFO beam resting on a constant Winkler elastic foundation is almost the same as of a composite beam with different fiber orientations for large values of Winkler elastic modulus, and fiber orientations has less effect on the natural frequency parameter. The interesting results show that normalized natural frequency of the CGFO beam is smaller than that of a similar discrete laminate beam and tends to the discrete laminated beam with increasing layers. It is believed that new results are presented for vibrational behavior of CGFO beams are of interest to the scientific and engineering community in the area of engineering design. پرونده مقاله -
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35 - Free Vibration Analysis of Moderately Thick Functionally Graded Plates with Multiple Circular and Square Cutouts Using Finite Element Method
J Vimal R.K Srivastava A.D Bhatt A.K SharmaA simple formulation for studying the free vibration of shear-deformable functionally graded plates of different shapes with different cutouts using the finite element method is presented. The aim is to fill the void in the available literature with respect to the free چکیده کاملA simple formulation for studying the free vibration of shear-deformable functionally graded plates of different shapes with different cutouts using the finite element method is presented. The aim is to fill the void in the available literature with respect to the free vibration results of functionally graded plates of different shapes with different cutouts. The material properties of the plates are assumed to vary according to a power law distribution in terms of the volume fraction of the constituents. Validation of the formulation is done with the help of convergence studies with respect to the number of nodes and the results are compared with those from past investigations available only for simpler problems. In this paper rectangular, trapezoidal and circular plates with cutouts are studied and the effects of volume fraction index, thickness ratio and different external boundary conditions on the natural frequencies of plates are studied. پرونده مقاله -
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36 - Electro-Thermo-Mechanical Vibration Analysis of a Foam-Core Smart Composite Cylindrical Shell Containing Fluid
A Ghorbanpour Arani R KolahchiIn this study, free vibration of a foam-core orthotropic smart composite cylindrical shell (SCCS) filled with a non-viscous compressible fluid, subjected to combined electro-thermo-mechanical loads is investigated. Piezoelectric polymeric cylindrical shell, is made from چکیده کاملIn this study, free vibration of a foam-core orthotropic smart composite cylindrical shell (SCCS) filled with a non-viscous compressible fluid, subjected to combined electro-thermo-mechanical loads is investigated. Piezoelectric polymeric cylindrical shell, is made from polyvinylidene fluoride (PVDF) and reinforced by armchair double walled boron nitride nanotubes (DWBNNTs). Characteristics of the equivalent composite are determined using micro-electro-mechanical models. The poly ethylene (PE) foam-core is modeled based on Winkler and Pasternak foundations. Employing the charge equation for coupling electrical and mechanical fields, the problem is turned into an eigenvalue one, for which analytical frequency equations are derived considering free electrical and simply supported mechanical boundary conditions at circular surfaces at either ends of the cylindrical shell. The influence of electric potential generated, filled-fluid, orientation angle of DWBNNTs, foam-core and a few other parameters on the resonance frequency of SCCS are investigated. Results show that SCCS and consequently the generated Φ improve sensor and actuator applications in several process industries, because it not only increases the vibration frequency, but also extends economic viability of the smart structure. پرونده مقاله -
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37 - 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 چکیده کاملIn 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. پرونده مقاله -
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38 - A Power Series Solution for Free Vibration of Variable Thickness Mindlin Circular Plates with Two-Directional Material Heterogeneity and Elastic Foundations
M.M Alipour M ShariyatIn the present paper, a semi-analytical solution is presented for free vibration analysis of circular plates with complex combinations of the geometric parameters, edge-conditions, material heterogeneity, and elastic foundation coefficients. The presented solution cover چکیده کاملIn the present paper, a semi-analytical solution is presented for free vibration analysis of circular plates with complex combinations of the geometric parameters, edge-conditions, material heterogeneity, and elastic foundation coefficients. The presented solution covers many engineering applications. The plate is assumed to have a variable thickness and made of a heterogeneous material whose properties vary in both radial and transverse directions. While the edge is simply-supported, clamped, or free; the bottom surface of the plate is resting on a two-parameter (Winkler-Pasternak) elastic foundation. A comprehensive sensitivity analysis including evaluating effects of various parameters is carries out. Mindlin theory is employed for derivation of the governing equations whereas the differential transform method is used to solve the resulted equations. In this regard, both the in-plane and rotary inertia are considered. Results show that degradations caused by a group of the factors (e.g., the geometric parameters) in the global behavior of the structure may be compensated by another group of factors of different nature (e.g, the material heterogeneity parameters). Moreover, employing the elastic foundation leads to higher natural frequencies and postponing the resonances. پرونده مقاله -
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39 - An Exact Solution for Vibration Analysis of Soft Ferromagnetic Rectangular Plates Under the Influence of Magnetic Field with Levy Type Boundary Conditions
S.A Mohajerani A Mohammadzadeh M Nikkhah BahramiIn this paper vibration of ferromagnetic rectangular plates which are subjected to an inclined magnetic field is investigated based on classical plate theory and Maxwell equations. Levy type solution and Finite element method using Comsol software are used to obtain the چکیده کاملIn this paper vibration of ferromagnetic rectangular plates which are subjected to an inclined magnetic field is investigated based on classical plate theory and Maxwell equations. Levy type solution and Finite element method using Comsol software are used to obtain the frequency of the plate subjected to different boundary conditions, good agreements is obtained when computed results are compared with those obtained by Comsol software, the results have shown that the frequency of the plates increases with the magnetic field and the effect of magnetic field is similar to the Winkler’s foundation. پرونده مقاله -
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40 - Free Vibration Analysis of Continuously Graded Fiber Reinforced Truncated Conical Shell Via Third-Order Shear Deformation Theory
M.H Yas M Nejati A AsanjaraniThis paper deals with free vibration analysis of continuously graded fiber reinforced (CGFR) truncated conical shell based on third-order shear deformation theory (TSDT), by developing special power-law distributions. The orthotropic (CGFR) truncated conical shell are c چکیده کاملThis paper deals with free vibration analysis of continuously graded fiber reinforced (CGFR) truncated conical shell based on third-order shear deformation theory (TSDT), by developing special power-law distributions. The orthotropic (CGFR) truncated conical shell are clamped and simply supported at the both ends. It is assumed to have a smooth variation of fibers volume fraction in the thickness direction. Symmetric and classic volume fraction profiles are examined. The appropriate displacement functions which identically satisfy the axisymmertic conditions are used to simplify the motion equations to a set of coupled ordinary differential equation with variable coefficients, which can be solved by generalized differential quadrature method (GDQM), to obtain the natural frequencies. The fast rate of convergence of the method is observed. To validate the results, comparisons are made with the available solutions for isotropic and CGM isotropic truncated conical shells. The effect of various geometrical parameters on the vibrational behavior of the CGFR truncated conical shell is investigated. This literature mainly contributes to illustrate the impact of the power-law distributions on the vibrarional behavior of orthotropic continuous grading truncated conical shell. This paper is also supposed to present useful results for continuouly graded fibers volume fraction in the thickness direction of a truncated conical shell and comparison with similar discrete laminated composite one. پرونده مقاله -
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41 - Calculation of Natural Frequencies of Bi-Layered Rotating Functionally Graded Cylindrical Shells
I Fakhari GolpayeganiIn this paper, an exact analytical solution for free vibration of rotating bi-layered cylindrical shell composed of two independent functionally graded layers was presented. The thicknesses of the shell layers were assumed to be equal and constant. The material properti چکیده کاملIn this paper, an exact analytical solution for free vibration of rotating bi-layered cylindrical shell composed of two independent functionally graded layers was presented. The thicknesses of the shell layers were assumed to be equal and constant. The material properties of the constituents of bi-layered FGM cylindrical shell were graded in the thickness direction of the layers of the shell according to a volume fraction power-law distribution. In order to derive the equations of motion, the Sanders’ thin shell theory and Rayleigh-Ritz method were used. Also the results were extracted by considering Coriolis, centrifugal and initial hoop tension effects. Effects of rotating speed, geometrical parameters, and material distribution in the two functionally graded layers of the shell, circumferential and longitudinal wave number on the forward and backward natural frequencies were investigated. A comparison of the results was made with those available in the literature for the validity and accuracy of the present methodology. پرونده مقاله -
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42 - Surface Effects on Free Vibration Analysis of Nanobeams Using Nonlocal Elasticity: A Comparison Between Euler-Bernoulli and Timoshenko
Sh Hosseini – Hashemi M Fakher R NazemnezhadIn this paper, surface effects including surface elasticity, surface stress and surface density, on the free vibration analysis of Euler-Bernoulli and Timoshenko nanobeams are considered using nonlocal elasticity theory. To this end, the balance conditions between nanob چکیده کاملIn this paper, surface effects including surface elasticity, surface stress and surface density, on the free vibration analysis of Euler-Bernoulli and Timoshenko nanobeams are considered using nonlocal elasticity theory. To this end, the balance conditions between nanobeam bulk and its surfaces are considered to be satisfied assuming a linear variation for the component of the normal stress through the nanobeam thickness. The governing equations are obtained and solved for Silicon and Aluminum nanobeams with three different boundary conditions, i.e. Simply-Simply, Clamped-Simply and Clamped-Clamped. The results show that the influence of the surface effects on the natural frequencies of the Aluminum nanobeams follows the order CC پرونده مقاله -
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43 - 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 چکیده کاملIn 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. پرونده مقاله -
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44 - Influence of the Elastic Foundation on the Free Vibration and Buckling of Thin-Walled Piezoelectric-Based FGM Cylindrical Shells Under Combined Loadings
M Mohammadimehr M Moradi A LoghmanIn this paper, the influence of the elastic foundation on the free vibration and buckling of thin-walled piezoelectric-based functionally graded materials (FGM) cylindrical shells under combined loadings is investigated. The equations of motion are obtained by using the چکیده کاملIn this paper, the influence of the elastic foundation on the free vibration and buckling of thin-walled piezoelectric-based functionally graded materials (FGM) cylindrical shells under combined loadings is investigated. The equations of motion are obtained by using the principle of Hamilton and Maxwell's equations and the Navier's type solution used to solve these equations. Material properties are changed according to power law in the direction of thickness. In this study, the effects of Pasternak elastic foundation coefficients and also the effects of material distribution, geometrical ratios and loading conditions on the natural frequencies are studied. It is observed that by increasing Pasternak elastic medium coefficients, the natural frequencies of functionally graded piezoelectric materials (FGPM) cylindrical shell always increases. The mode shapes of FGPM cylindrical shell has been shown in this research and the results show that the distribution of the radial displacements is more significant than circumferential and longitudinal displacements. پرونده مقاله -
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45 - On the Analysis of FGM Beams: FEM with Innovative Element
M Zakeri A Modarakar Haghighi R AttarnejadThis paper aims at presenting a new efficient element for free vibration and instability analysis of Axially Functionally Graded Materials (FGMs) non-prismatic beams using Finite Element Method (FEM). Using concept of Basic Displacement Functions (BDFs), two- node eleme چکیده کاملThis paper aims at presenting a new efficient element for free vibration and instability analysis of Axially Functionally Graded Materials (FGMs) non-prismatic beams using Finite Element Method (FEM). Using concept of Basic Displacement Functions (BDFs), two- node element extends to three-node element for obtaining much more exact results using FEM. First, BDFs are introduced and computed using energy method such as unit-dummy load method. Afterward, new efficient shape functions are developed in terms of BDFs during the procedure based on the mechanical behavior of the element in which presented shape functions benefit generality and accuracy from stiffness and force method, respectively. Finally, deriving structural matrices of the beam with respect to new shape functions; free vibration and instability analysis of the FGM beam are studied using finite element method for all types of AFGM beams and the convergence of FEM has been studied. The results from both free vibration and instability analysis are in perfect agreement with those of previously published. پرونده مقاله -
دسترسی آزاد مقاله
46 - Three-dimensional Free Vibration Analysis of a Transversely Isotropic Thermoelastic Diffusive Cylindrical Panel
R Kumar T KansalThe present paper is aimed to study an exact analysis of the free vibrations of a simply supported, homogeneous, transversely isotropic, cylindrical panel based on three-dimensional generalized theories of thermoelastic diffusion. After applying the displacement potenti چکیده کاملThe present paper is aimed to study an exact analysis of the free vibrations of a simply supported, homogeneous, transversely isotropic, cylindrical panel based on three-dimensional generalized theories of thermoelastic diffusion. After applying the displacement potential functions in the basic governing equations of generalized thermoelastic diffusion, it is noticed that a purely transverse mode is independent of thermal and concentration fields and gets decoupled from the rest of motion. The equations for free vibration problem are reduced to four equations of second-order and one fourth-order ordinary differential equation after expanding the displacement potential, temperature change and concentration functions with an orthogonal series. The formal solution of this system of equations can be expressed by using modified Bessel function with complex arguments. The numerical results for lowest frequency have been obtained and presented graphically. The effect of diffusion on lowest frequency has also been presented graphically. Some special cases of secular equation are also discussed. پرونده مقاله -
دسترسی آزاد مقاله
47 - Static and Free Vibration Analyses of Orthotropic FGM Plates Resting on Two-Parameter Elastic Foundation by a Mesh-Free Method
H Momeni-KhabisiIn this paper, static and free vibrations behaviors of the orthotropic functionally graded material (FGM) plates resting on the two-parameter elastic foundation are analyzed by the a mesh-free method based on the first order shear deformation plate theory (FSDT). The me چکیده کاملIn this paper, static and free vibrations behaviors of the orthotropic functionally graded material (FGM) plates resting on the two-parameter elastic foundation are analyzed by the a mesh-free method based on the first order shear deformation plate theory (FSDT). The mesh-free method is based on moving least squares (MLS) shape functions and essential boundary conditions are imposed by transfer function method. The orthotropic FGM plates are made of two orthotropic materials and their volume fractions are varied smoothly along the plate thickness. The convergence of the method is demonstrated and to validate the results, comparisons are made with finite element method (FEM) and the others available solutions for both homogeneous and FGM plates then numerical examples are provided to investigate the effects of material distributions, elastic foundation coefficients, geometrical dimensions, applied force and boundary conditions on the static and vibrational characteristics of the orthotropic FGM plates. پرونده مقاله -
دسترسی آزاد مقاله
48 - 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 چکیده کاملIn 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. پرونده مقاله -
دسترسی آزاد مقاله
49 - 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 چکیده کاملThe 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. پرونده مقاله -
دسترسی آزاد مقاله
50 - 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 چکیده کاملIn 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. پرونده مقاله -
دسترسی آزاد مقاله
51 - Free Axisymmetric Bending Vibration Analysis of two Directional FGM Circular Nano-plate on the Elastic Foundation
M Zarei Gh RahimiIn the following paper, free vibration analysis of two directional FGM circular nano-plate on the elastic medium is investigated. The elastic modulus of plate varies in both radial and thickness directions. Eringen’s theory was employed to the analysis of circular چکیده کاملIn the following paper, free vibration analysis of two directional FGM circular nano-plate on the elastic medium is investigated. The elastic modulus of plate varies in both radial and thickness directions. Eringen’s theory was employed to the analysis of circular nano-plate with variation in material properties. Simultaneous variations of the material properties in the radial and transverse directions are described by a general function. Ritz functions were utilized to obtain the frequency equations for simply supported and clamped boundary. Differential transform method also used to develop a semi-analytical solution the size-dependent natural frequencies of non-homogenous nano-plates. Both methods reported good results. The validity of solutions was performed by comparing present results with themselves and those of the literature for both classical plate and nano-plate. Effect of non-homogeneity on the nonlocal parameter, geometries, boundary conditions and elastic foundation parameters is examined the paper treats some interesting problems, for the first time. پرونده مقاله -
دسترسی آزاد مقاله
52 - تحلیل ارتعاشات آزاد تیر تیموشینکو ساخته شده از مواد تابعی دو بعدی
محمد رحیم ترشیزیان عبدالحسین اخوت پوردر این تحقیق ارتعاشات آزاد یک تیر از جنس ماده تابعی دو بعدی با در نظر گرفتن تئوری تیر تیموشینکو بررسی شده است. تغییرات خواص مواد در دو جهت ضخامت و طول تیر به صورت تابع نمائی فرض شده است. معادلات حرکت با استفاده از اصل همیلتون بدست آمده که در آن اثر اینرسی های عمودی و دو چکیده کاملدر این تحقیق ارتعاشات آزاد یک تیر از جنس ماده تابعی دو بعدی با در نظر گرفتن تئوری تیر تیموشینکو بررسی شده است. تغییرات خواص مواد در دو جهت ضخامت و طول تیر به صورت تابع نمائی فرض شده است. معادلات حرکت با استفاده از اصل همیلتون بدست آمده که در آن اثر اینرسی های عمودی و دورانی نیز در نظر گرفته شده است. حل معادلات حرکت از روش لوی با رهیافتی از روش فضای حالت انجام گرفته و فرکانس های طبیعی تیر محاسبه شده اند. اثر تغییرات نسبت طول به ضخامت تیر، پارامتر های غیر همگونی ماده و شرایط مرزی، بر روی فرکانس های طبیعی تیر بررسی گردیده است. نتایج نشان می دهد، با افزایش نسبت طول به ضخامت تیر فرکانس های طبیعی افزایش می یابد و همچنین مقدار فرکانس های طبیعی برای تیر از ماده تابعی دو بعدی در شرایط یکسان بیشتر از مقدار آن در تیر از ماده تابعی یک بعدی می باشد. پرونده مقاله -
دسترسی آزاد مقاله
53 - تحلیل ارتعاشات و کنترل میکروتیر یکسر گیردار به همراه لایه های عملگر و حسگر پیزوالکتریک با فرض اثرات سطح
سید علی افتخاری محمد خواجه خباز محمد هاشمیانامروزه پیش‌بینی رفتار ارتعاشی و دینامیکی سازه‌های میکرو مورد توجه بسیاری از پژوهشگران قرار گرفته است. در این پژوهش تحلیل ارتعاشات و کنترل میکروتیر یکسر گیردار به همراه لایه‌های پیزوالکتریک عملگر و حسگر با فرض اثرات تنش سطح مورد ارزیابی قرار گرفته است. معادلات دیفرانسیل چکیده کاملامروزه پیش‌بینی رفتار ارتعاشی و دینامیکی سازه‌های میکرو مورد توجه بسیاری از پژوهشگران قرار گرفته است. در این پژوهش تحلیل ارتعاشات و کنترل میکروتیر یکسر گیردار به همراه لایه‌های پیزوالکتریک عملگر و حسگر با فرض اثرات تنش سطح مورد ارزیابی قرار گرفته است. معادلات دیفرانسیل حاکم با استفاده از روش انرژی و اصل همیلتون استخراج شده و از روش مجموع مربعات دیفرانسیلی تعمیم یافته برای گسسته-سازی و تبدیل معادلات دیفرانسیل پاره‌ای به دسته معادلات دیفرانسیل معمولی استفاده شده است. اثر تغییرات هندسه مدل و مدول الاستیسیته سطح، تنش پسماند سطح و چگالی سطحی بر فرکانس طبیعی مدل میکروتیر با لایه‌های پیزوالکتریک بررسی شده است. همچنین تأثیر طراحی کنترلر بهینه خطی بر تغییرات پاسخ دینامیکی و ولتاژ کنترلی پیزوالکتریک مورد ارزیابی قرار گرفته است. نتایج نشان دهنده‌ی افزایش سرعت پاسخ و کاهش سریعتر دامنه ارتعاشی مدل با طراحی کنترل بهینه خطی است. پرونده مقاله -
دسترسی آزاد مقاله
54 - آنالیز ارتعاش آزاد نانولوله‌های ویسکوالاستیک تحت میدان مغناطیسی طولی بر اساس گرادیان کرنش غیرموضعی مدل تیر تیموشنکو
پرویز قزوینیاندر این مقاله ارتعاش آزاد نانولوله‌های ویسکوالاستیک تحت میدان مغناطیسی طولی مورد بررسی قرار گرفته است. معادله حاکم با استفاده از مدل تیر تیموشنکو و مدل کلوین-ویت بر اساس تئوری گرادیان کرنش غیرموضعی فرمول‌بندی شده است. در رویه آنالیز از روش تربیع دیفرانسیلی تطبیقی موضعی ( چکیده کاملدر این مقاله ارتعاش آزاد نانولوله‌های ویسکوالاستیک تحت میدان مغناطیسی طولی مورد بررسی قرار گرفته است. معادله حاکم با استفاده از مدل تیر تیموشنکو و مدل کلوین-ویت بر اساس تئوری گرادیان کرنش غیرموضعی فرمول‌بندی شده است. در رویه آنالیز از روش تربیع دیفرانسیلی تطبیقی موضعی (LADQM) استفاده شده است. همچنین اثر پارامترهای غیرموضعی، ضریب استهلاک سازه‌ای، پارامتر مقیاس طول ماده و میدان مغناطیسی طولی بر فرکانس‌های طبیعی سیستم مورد بررسی قرار گرفته است. ممکن است نتایج این تحقیق برای درک کاربرد بالقوه نانولوله‌ها در سیستم نانو الکترومکانیکی مفید باشد. پرونده مقاله -
دسترسی آزاد مقاله
55 - تحلیل ارتعاش آزاد عرضی کابل با استفاده از روش جدا سازی ادمین
رضا احراری محمد شادکامی محمد حسین ابوالبشریدر این مقاله روش جداسازی ادمین به منظور بررسی ارتعاش آزاد یک کابل دو تکه به کار گرفته شده است. هر قسمت از کابل به صورت مجزا توسط این روش تحلیل شده است. با اعمال شرایط پیوستگی و شرایط مرزی، فرکانس های طبیعی و شکل مدهای مربوطه به سادگی و به صورت هم زمان به دست می آید. با چکیده کاملدر این مقاله روش جداسازی ادمین به منظور بررسی ارتعاش آزاد یک کابل دو تکه به کار گرفته شده است. هر قسمت از کابل به صورت مجزا توسط این روش تحلیل شده است. با اعمال شرایط پیوستگی و شرایط مرزی، فرکانس های طبیعی و شکل مدهای مربوطه به سادگی و به صورت هم زمان به دست می آید. با ارائه چند مثال برای شرایط مرزی مختلف، این مقادیر محاسبه شده اند. نتایج به دست آمده از راه حل های تحلیلی و عددی ذکر شده در مقاله با دقت خوبی نتایج حاصله از این روش را تایید می نمایند و مشخص می کنند که روش ادمین یک روش موثر و قابل اطمینان بوده و نسبت به سایر تحلیل های ارتعاشی کارآمدتر و ساده تر می باشد. در بخش پایانی، تاثیر میزان پارامترهای جرم و سختی فنر در شرایط مرزی بر میزان و نحوه تغییرات فرکانس های طبیعی بررسی شده و یک راهکار موثر برای برخورد با این گونه شرایط مرزی پیشنهاد شده است. پرونده مقاله -
دسترسی آزاد مقاله
56 - Free vibration analysisof soft-core composite-faced sandwich plates using three-dimensional finite element method
Mohammad Mahdi Kheirikhah Hasan Aghabarati Pooneh KhosraviIn this paper, natural frequencies of the sandwich plates with soft flexible core and composite face sheets are obtained. Three-Dimensional (3D) finite element method (FEM) is used for constructing and analyzing of the sandwich plates to obtain their natural frequencies چکیده کاملIn this paper, natural frequencies of the sandwich plates with soft flexible core and composite face sheets are obtained. Three-Dimensional (3D) finite element method (FEM) is used for constructing and analyzing of the sandwich plates to obtain their natural frequencies. Continuity conditions for transverse shear stresses at the interfaces as well as transverse flexibility and transverse normal strain and stress of the core are considered.The effects of plate dimensions such as aspect ratio and thickness ratio are studied. Also, different boundary conditions such as all edges clamped (CCCC), all edges simply supported (SSSS) and combined boundary conditions including (CFCF)are applied to the sandwich plates. Comparison of the present results in special case with those of the accurate plate theories confirms the accuracy of the proposedmodel. پرونده مقاله -
دسترسی آزاد مقاله
57 - Implementing Basic Displacement Function to Analyze Free Vibration Rotation of Non-Prismatic Euler-Bernoulli Beams
Pouria Hajikarimi Reza AttarnejadRotating beams have been considerably appealing to engineers and designers of complex structures i.e. aircraft’s propeller and windmill turbines. In this paper, a new flexibility-based method is proposed for the dynamic analysis of rotating non-prismatic Euler-Ber چکیده کاملRotating beams have been considerably appealing to engineers and designers of complex structures i.e. aircraft’s propeller and windmill turbines. In this paper, a new flexibility-based method is proposed for the dynamic analysis of rotating non-prismatic Euler-Bernoulli beams. The flexibility basis of the method ensures the true satisfaction of equilibrium equations at any interior point of the elements. Following structural/mechanical principles, exact shape functions and consequently exact structural matrices i.e. consistent mass, geometric stiffness and flexural stiffness matrices are derived in terms of special so-called “Basic Displacement Functions”. The method is considered as the logical extension of conventional finite element method. Being straightforward formulated, the method can be incorporated into any standard finite element programs. The method poses no restrictions on either type of cross-section or variation of cross-sectional dimensions. The effects of rotational speed parameter and taper ratio on the variation of natural frequencies are studied and the results compare well with the other existing methods in the technical literature. پرونده مقاله -
دسترسی آزاد مقاله
58 - Free Vibration Analysis of Sandwich Plates with FGM Face Sheets and Temperature-Dependent Properties of the Core Materials
Y. MohammadiIn this paper, the free vibration of sandwich plates with power-law FGM face sheets in various thermal environments is performed by high-order sandwich plate theory. The material properties of the core, such as Young’s modulus, density, thermal expansion coefficie چکیده کاملIn this paper, the free vibration of sandwich plates with power-law FGM face sheets in various thermal environments is performed by high-order sandwich plate theory. The material properties of the core, such as Young’s modulus, density, thermal expansion coefficient and Poisson’s ratio, are assumed to be temperature dependent by nonlinear function of temperature [1]. The material properties of the FGM face sheets are assumed to vary continuously through the thickness according to a power law distribution in terms of volume fractions of the constituents [2]. The governing equations of motion in free natural vibration are derived using Hamilton’s principle [3]. A new approach is used to reduce the equations of motion from twenty three equations to eleven equations and then solve them. The new solution approach consists of isolating six of the unknowns in the displacements of the face sheets using the compatibility equations, followed by isolating the additional six Lagrange multipliers using the equations of the face sheets, finally, the isolated unknowns are substituted into the eleven equations of the core. Both un-symmetric and symmetric sandwich plates are considered in this analysis. Good agreement is found between theoretical predictions of the fundamental frequency parameters and the results obtained from other references for simply supported sandwich plates with functionally graded face sheets. The results show that the fundamental frequency parameters (ω ̅ ) increases by increasing the volume fraction index (κ). Also, the effect of temperature on the value of fundamental frequency parameters decreases with increases in the FGM face sheets thickness. The results also revealed that as the side-to-thickness ratio (b⁄h), the core-to-face sheet thickness ratio (h_c⁄h_t ) and temperature changes, have a significant effect on the fundamental frequency parameters. پرونده مقاله -
دسترسی آزاد مقاله
59 - Simulation and Analysis of Sandwich Panels Free Vibration with Corrugated Core Based on Galerkin Method
Gholamreza Banadcooki J. RezaeiPazhandThis paper aims to evaluate sandwich panels' free vibration with corrugated core by Element-free Galerkin methods and based on first order shear deformation theory (FSDT) investigated. The sandwich panels' free vibration with corrugated core consist of two sheets above چکیده کاملThis paper aims to evaluate sandwich panels' free vibration with corrugated core by Element-free Galerkin methods and based on first order shear deformation theory (FSDT) investigated. The sandwich panels' free vibration with corrugated core consist of two sheets above and below the panels, and a corrugated core in middle of these panels. The core equals to orthotropic sheet and the two panels equal to isotropic sheet. Dynamic equations of the members are obtained through first order shear deformation theory. The present research applies Galerkin numerical elementless method to solve equations of the problems. This method uses the functions of minimum moving squares. The model is simulated in cosmos software; the results are compared with the results of present papers, and show the accuracy of the method applied in the present paper. پرونده مقاله -
دسترسی آزاد مقاله
60 - Analysis of Free Vibration Sandwich Panels with trapezoidal Corrugated Core Based on Galerkin Method
Arman Gholamreza BanadCooki J.Rezaei PazhandThe purpose of this paper is to evaluate the free vibration of sandwich panels with corrugated core using the element-free Galerkin method and based on the first-order shear deformation theory (FSDT).The sandwich panels' free vibrations with corrugated core consist of t چکیده کاملThe purpose of this paper is to evaluate the free vibration of sandwich panels with corrugated core using the element-free Galerkin method and based on the first-order shear deformation theory (FSDT).The sandwich panels' free vibrations with corrugated core consist of two sheets above and below the panels, and a corrugated core in middle of these panels. The core equals to orthotropic sheet and the two panels equal to isotropic sheet. Dynamic equations of the members are obtained through FSDT. The present research applies Galerkin numerical element less method to solve equations of the problems. This method uses the functions of minimum moving squares. The model is simulated in cosmos software; the results are compared with the results of present papers, and show the accuracy of the method applied in the present paper. پرونده مقاله -
دسترسی آزاد مقاله
61 - Formulation of a new finite element based on assumed strains for membrane structures
Lahcene Fortas Lamine Belounar Tarek MerzoukiAbstractIn this paper, a new triangular membrane finite element with in-plane drilling rotation has been developed using the strainbasedapproach for static and free vibration analyses. The proposed element, having three degrees of freedom at each of thethree corner node چکیده کاملAbstractIn this paper, a new triangular membrane finite element with in-plane drilling rotation has been developed using the strainbasedapproach for static and free vibration analyses. The proposed element, having three degrees of freedom at each of thethree corner nodes, is based on assumed strain functions satisfying both compatibility and equilibrium equations. Numericalinvestigations have been conducted using several tests, including static and free vibration problems, and the obtained resultsare compared with analytical and numerical available solutions. It is found that efficient convergence characteristics andaccurate results can be achieved using the developed element. پرونده مقاله -
دسترسی آزاد مقاله
62 - Free Vibration of Simply Supported Rectangular Composite Plates with Patch Mass
ر. اکبری آلاشتی ر. علی بخشیThe effect of a distributed patch mass on the natural frequency of vibration of a laminated rectangular plate with simply supported boundaries is investigated. The third order displacement field of a composite laminated rectangular plate is defined using the two variabl چکیده کاملThe effect of a distributed patch mass on the natural frequency of vibration of a laminated rectangular plate with simply supported boundaries is investigated. The third order displacement field of a composite laminated rectangular plate is defined using the two variable refined plate theory. Equations of motion of the plate are obtained with the help of calculus of variation. Parametric study of non-dimensional natural frequencies of vibration is carried out and the effects of geometrical parameters such as the aspect ratio of the plate, size and location of the patch mass on these frequencies are studied. The results are then compared with those reported using the third order shear deformation theory. The results are found to be in very good agreement. پرونده مقاله -
دسترسی آزاد مقاله
63 - Free Vibration Analysis of Thick Functionally Graded Rectangular Plates Using Variable Refined Plate Theory
رضا علی بخشی احمد خاواجیIn this paper, free vibration of functionally graded rectangular simply supported thick plates based on two variable refined plate theory is presented. According to a power-law distribution, the mass density and elasticity modulus of the plate are considered to vary whi چکیده کاملIn this paper, free vibration of functionally graded rectangular simply supported thick plates based on two variable refined plate theory is presented. According to a power-law distribution, the mass density and elasticity modulus of the plate are considered to vary while Poisson’s ratio is constant. In order to extract the five constitutive equations of motion, Hamilton principle is employed. The high accuracy of this theory is investigated by comparing with exact results reported by higher order shear deformation theory. Furthermore, parametric study of non-dimensional natural frequencies is carried out and the influences of geometrical parameters such as aspect ratios of the plate on these frequencies are studied. پرونده مقاله -
دسترسی آزاد مقاله
64 - Free vibration analysis of circular sandwich plates with clamped FG face sheets
یونس محمدی کیوان حسینی صفری محسن رحمانیFree vibration of sandwich plates with temperature dependent functionally graded (FG) face sheets in various thermal environments is investigated. The material properties of FG face sheets are assumed to be temperature-dependent and vary continuously through the thickne چکیده کاملFree vibration of sandwich plates with temperature dependent functionally graded (FG) face sheets in various thermal environments is investigated. The material properties of FG face sheets are assumed to be temperature-dependent and vary continuously through the thickness according to a power-law distribution in terms of the volume fractions of the constituents. Also, the material properties of the core are assumed to be temperature dependent. The governing equations of motion in polar system and in free natural vibration are derived using Hamilton’s principle and Galerkin method is used to solve the equations and obtain the natural frequency. In-plane stresses of the core that usually are ignored in the vibration characteristics of the sandwich structures are considered in this formulation. The results obtained by Galerkin method for symmetric circular sandwich plate with fixed support is compared with finite element method that obtained by ABAQUS and good agreement is found. The results show that varying the power-law index and temperature have important effects on natural frequency. پرونده مقاله -
دسترسی آزاد مقاله
65 - Free vibration Study of simply supported cylindrical laminateds panels with piezoelectric layer
مصطفی معطری فرزان براتیIn the present study, vibration of cylindrical laminates with different layers and angles were studied. In order to actuate and polarize in radial direction, a piezoelectric layer was located at outer surface of composite shell. Laminates were assumed long enough so tha چکیده کاملIn the present study, vibration of cylindrical laminates with different layers and angles were studied. In order to actuate and polarize in radial direction, a piezoelectric layer was located at outer surface of composite shell. Laminates were assumed long enough so that plane strain state analysis in 2D can be used properly. In order to satisfy the boundary conditions, variables in terms of Fourier series were obtained. The governing equations reduced to ordinary differential equations at thickness direction and by power series method, the exact solution equations were obtained, unknown coefficient were calculated with rapid convergence. By using the matrix transfer method, vibration response of composite shell were obtained. Finally, results for the first seven modes of natural frequency of multi layer cylindrical shell were obtained. In addition, for both state of one single piezoelectric layer and five layer shell at the end, variable response such as displacement, principal stress and strain were achieved. پرونده مقاله -
دسترسی آزاد مقاله
66 - Free Vibration Analysis of Sandwich Micro Beam with Piezoelectric Based on Modified Couple Stress Theory and Surface Effects
Mohammad khajekhabaz Ali Eftekhari Mohammad HashemianIn this paper, the free vibration analysis of sandwich micro beam with piezoelectric layers based on the modified couple stress and surface elasticity theories are investigated. The Hamilton’s principle is employed to derive the sandwich micro beam with piezoelect چکیده کاملIn this paper, the free vibration analysis of sandwich micro beam with piezoelectric layers based on the modified couple stress and surface elasticity theories are investigated. The Hamilton’s principle is employed to derive the sandwich micro beam with piezoelectric based on modified couple stress theory incorporating with Gurtin- Murdoch surface theory. The generalized differential quadrature method is used to discretize the partial differential equation into the ordinary differential equation. The effect of various parameters such as thickness to material length scale parameter ratio, the surface residual stress, Young's modulus of surface layer, surface mass density and surface piezoelectric constant are investigated by comparing the results obtained using the modified couple and classical theories. Numerical results of this problem evaluate the effect of micro length scale parameters on natural frequency. The results show that surface parameter effects are significant when the model is small, but can be neglected with increasing model size. پرونده مقاله -
دسترسی آزاد مقاله
67 - Vibration Analysis of Timoshenko Beam reinforced with Boron-Nitride Nanotube on Elastic Bed
ایلدا عبداللهی محمدحسین یاسIn this paper, free vibration analysis of a polymer-based nano-composite beam reinforced by boron-nitride nanotubes and subjected on elastic foundation, is studied. Smooth and defect-free nanotubes with uniform and directly- orientated in matrix are intended. Also, nano چکیده کاملIn this paper, free vibration analysis of a polymer-based nano-composite beam reinforced by boron-nitride nanotubes and subjected on elastic foundation, is studied. Smooth and defect-free nanotubes with uniform and directly- orientated in matrix are intended. Also, nanotubes’ distribution in the thickness direction of beam is regarded as a uniform distribution of the three different targeted ones. The properties of nano-beam are obtained by using a micromechanical model. The governing equations based on Timoshenko beam theory are derived by using the Hamilton principle. The equations are solved by the extended differential Quadrature and the natural frequencies are obtained. The effect of various parameters such as volume fraction of nanotubes, carbon-nanotube (CNT) distribution in the thickness direction of the beam, elastic media, boundary conditions and the aspect ratio is investigated on the natural frequency. The results show that a change on these parameters has a significant impact on the natural frequency. پرونده مقاله -
دسترسی آزاد مقاله
68 - Free and Forced Vibration Analysis of Composite Laminated Conical Shells under Different Boundary Conditions Via Galerkin Method
آیدین نصیری راد رضا انصاری حسام روحیIn this paper, natural frequency and response of forced vibration of composite laminated conical shells under different boundary conditions are investigated. To this end, equations of Donnell's thin shell theory are used as governing equations. The analytical Galerkin m چکیده کاملIn this paper, natural frequency and response of forced vibration of composite laminated conical shells under different boundary conditions are investigated. To this end, equations of Donnell's thin shell theory are used as governing equations. The analytical Galerkin method together with beam mode shapes as weighting functions is employed to solve the problem. Due to importance of boundary conditions upon the mechanical behavior of conical shells, the analysis is carried out for all possible boundary conditions. The response of forced vibration is calculated via the modal participation factor method. Numerical comparisons of free vibration with the results in the open literature are made to validate the present methodology. پرونده مقاله -
دسترسی آزاد مقاله
69 - Fluid-structure Interaction Vibration Analysis of Vertical Cylindrical Containers with Elastic Bottom Plate Made of Functionally Graded Materials
علی اکبر شفیعی مجتبی محزون احسان عسکریIn the present paper a method is proposed to investigate the free vibration of a partially liquid-filled cylindrical tank. The mechanical properties of the container are assumed to change continuously along the thickness according to volume fraction Power-law, Sigmoid o چکیده کاملIn the present paper a method is proposed to investigate the free vibration of a partially liquid-filled cylindrical tank. The mechanical properties of the container are assumed to change continuously along the thickness according to volume fraction Power-law, Sigmoid or Exponential distribution. The liquid is supposed to be incompressible and in viscid and its velocity potential is formulated by using Eigen function expansions. The interaction between the liquid and the plate was considered and the dynamic characteristics of the plate are extracted by using the Rayleigh–Ritz method. The results from the proposed method are in good agreement with experimental and numerical solutions available in the literature. A finite element analysis is also applied to check the validity of the results. Furthermore, the influence of various variables such as the number of nodal circles and diameters, volume fractions of functionally graded materials and liquid level on the dynamic behavior of the coupled system is investigated. پرونده مقاله
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