In this research three-dimensional free vibration analysis of functionally graded circular plate with various boundary conditions is achieved. A semi-analytical method, which makes use of the state space method and the one-dimensional differential quadrature method, is used to obtain the vibration frequencies and dynamic responses of circular plates. Numerical results are given to demonstrate the accuracy and superiority of the presented method. The numerical results are compared with the existing numerical solutions and good agreement is displayed .Using the semi-analytical method, the analytical solution in the thickness direction is given and an effective approximate solution in the radial direction is obtained by selecting fewer discrete points. پرونده مقاله

In the recent paper, one of the numerical methods without element, for static analysis of thin plates displacement based on classical plates theory (CPT), has been presented. In this method, the domain of problem solving is shown only by the means of a set of nodes, and there is no need to any mesh scheme or element. One of the kinds of element free methods used here is the Radial Point Interpolation Method (RPIM). In order to access to the governing equations, the Hamilton principle is used in the form of Galerkin weak form. Using interpolating functions, the field variables, namely the displacement, are approximated, and by applying the governing equations, the convergence and the accuracy of the present method are studied. Results of the present method are compared with the results of the exact solution of analytical methods of plates and also with the finite element method (FEM). In addition, the effects of thickness ratio to length, appearance coefficient, and node distribution are discussed. پرونده مقاله

In the present article, the free vibration analysis of a multi-layer rectangular plate with two magneto-rheological (MR) fluid layers and a flexible core is investigated based on exponential shear deformation theory for the first time. In exponential shear deformation theory, exponential functions are used in terms of thickness coordinate to include the effect of transverse shear deformation and rotary inertia. The displacement of the flexible core is modeled using Frostig’s second order model which contains a polynomial with unknown coefficients. MR fluids viscosity can be varied by changing the magnetic field intensity. Therefore, they have the capability to change the stiffness and damping of a structure. The governing equations of motion have been derived using Hamilton`s principle. The Navier technique is employed to solve derived equations. To validate the accuracy of the derived equations, the results in a specific case are compared with available results in the literature, and a good agreement will be observed. Then, the effect of variation of some parameters such as magnetic field intensity, core thickness to panel thickness ratio and MR layer thickness to panel thickness ratio on natural frequency of the sandwich panel is investigated. پرونده مقاله

In this research, the thermal buckling analysis of a truncated conical shell made of porous materials on elastic foundation is investigated. The equilibrium equations and the conical shell`s stability equations are obtained by using the Euler`s and the Trefftz equations .Properties of the materials used in the conical shell are considered as porous foam made of steel, which is characterized by its non-uniform distribution of porous materials along the thickness direction. Initially, the displacement field relation based on the classical model for double-curved shell is expressed in terms of the Donnell`s assumptions. Non-linear strain-displacement relations are obtained according to the von Kármán assumptions by applying the Green-Lagrange strain relationship. Then, performing the Euler equations leads obtaining nonlinear equilibrium equations of cylindrical shell. The stability equations of conical shell are obtained based on neighboring equilibrium benchmark (adjacent state). In order to solve the stability equations, primarily, due to the existence of axial symmetry, we consider the cone crust displacement as a sinusoidal geometry, and then, using the generalized differential quadrature method, we solve them to obtain the critical temperature values of the buckling Future. In order to validate the results, they compare with the results of other published articles. At the end of the experiment, various parameters such as dimensions, boundary conditions, cone angle, porosity parameter and elastic bed coefficients are investigated on the critical temperature of the buckling. پرونده مقاله

In 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

In present study, the third-order shear deformation theory has been developed to investigate vibration analysis of FG Nano-plates based on Eringen nonlocal elasticity theory. The materials distribution regarding to the thickness of Nano-plate has been considered based on two different models of power function and exponential function. All equations governing on the vibration of FG Nano-plate have been derived from Hamilton’s principle. It has been also obtained the analytical solution for natural frequencies and corresponding mode shapes of simply supported FG Nano-plates. In addition, the general form of stiffness and mass matrix elements has been expressed based on this theory. The effect of different parameters such as power and exponential indexes of targeted function , nonlocal parameter of Nano-plate, aspect ratio and thickness to length ratio of Nano-plate on non-dimensional natural frequencies of free vibration responses have been investigated. The obtained analytical results show an excellent agreement with other available solutions of previous studies. The formulation and analytical results obtained from proposed method can be used as a benchmark for further studies to develop this area of research. پرونده مقاله

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Collapse by buckling a quite common phenomenon in sheets under pressure. When these structures caused by defects such as corrosion and cracks the time of the occurrence of this phenomenon is sensitive and critical load to be significantly reduced. Therefore, in this article sheet of aluminum Al 1200 by cracks in a part of the sheet will be considered. Left angle on the critical buckling load effect both experimentally and theoretically calculated. STM-250 experiments using theoretical analysis using Abaqus software is done and the results are compared with theoretical and experimental. پرونده مقاله

In this paper, the thermal buckling analysis of a circular plate made of FGM materials with actuator/actuator piezoelectric layers based on neutral plane, classical plate theory and first order shear deformation plate theory is investigated. Reddy's model is assumed for material properties of FGM plate. Plate under the thermal loading, nonlinear temperature rise through the thickness and clamped edges is considered. Equilibrium and stability equations are drived using the calculus of variations and applying Euler equations. The obtained results are compared with the numerical values of the critical buckling temperature based on the theories mentioned above, and good agreement is observed between them. پرونده مقاله

Bending analysis of FGM plates under uniform and sinusoidal loaded result in forth order partial differential equation. In this paper the analytical solution is based on the extended Kantorovich iterative procedure. The differential equations for the iterative procedure is derived using the Galerkin method. The solution was develope based on the classical plate’s theory (CLPT). The reliability of the present analytical method for FGM, under different boundary condition, was verified and approved when comparing Navier solution and finite element results with ANSYS solution. Since the FGM modeling is impossibility at ANSYS, a macro has used for modeling and analysis.The results show a high accuracy and the iterative process converges very rapidly. It was also found that the final form of the generated solutions is independent of the initial trial function. پرونده مقاله

In this paper the buckling coefficient of FGM rectangular plates calculated by the new version of differential quadrature method (DQM). At the first the governing differential equation for plate has been calculated and then according to the new version of differential quadrature method (DQM) the existence derivatives in equation , convert to the amounts of function in the grid points inside of the region is solved .With doing this , The equation will be converted to an eigen value problem and the buckling coefficient is obtained . In the solving of this problem two kinds of loading for all edges are simply supported or clamped are considered and also the effect of power law index over the buckling coefficient is considered . For the case Isotropic the results are compared well with finite element and finite difference results.This fact indicates that the new version of DQ method can be employed for obtaining buckling loads of plates subjected to non–uniform distributed loading for other boundary conditions. پرونده مقاله

In this paper, buckling of cylindrical grooved shells under axial load has been examined by theoretical and experimental methods. The shell is made of USA/API – X42 5L steel standards. This material is one of the most common materials used in gas, oil and petrochemical industries. The effect of spiral grooves on cylindrical shell was analyzed, and the results obtained from the Abaqus software were compared with experimental results. Theoretical and experimental results were in good agreement. Hence, the numerical results can be used as well. It was also found that the number of grooves on the critical buckling load has an important role so that the critical buckling load decreases with an increase in critical load groove. پرونده مقاله

در این مطالعه اثر تغییرات اقلیمی بر دما، بارندگی و رواناب در حوضه درودزن در شمال شرق استان فارس بررسی شده است. تغییرات دما و بارندگی در دو دوره آتی میانی و دور با استفاده از مدل 15 مدل گردش عمومی جو فاز 3 (CMIP3) ، تحت سه سناریو انتشار گازهای گلخانه ای A2، B1 و A1B ، ریز مقیاس نمای شده و مورد مطالعه قرار گرفت. تفاوت در میزان تغییرات دما و بارندگی در این دو دوره نسبت به مقادیر مشاهداتی در 15 مدل حاکی از وجود عدم قطعیت در نتایج می باشد. برای کاهش این عدم قطعیت و محدود کردن نتایج برای مدیریت و برنامه ریزی منابع آب، رویکرد گروهی مورد توجه قرار گرفت. برای تهیه رویکرد گروهی، از پارامترهای فایلهای سناریو 15 مدل فوق میانگین گرفته شد. به طوری که یک مدل جدید اقلیمی با عنوان میانگین گروهی چند مدله برای هر دوره به دست آمد. سپس روانابهای این دو دوره، تحت رویکرد مذکور، با استفاده از شبکه عصبی پیشخور تولید شد. نتایج نشان از افزایش میانگین ماهیانه دمای حداقل و حداکثر هر دو دوره تحت سه سناریو، دارد. در اکثر مدل ها، بارندگی در ماه های اولیه سال های میلادی کاهش و در فصل بهار افزایش، می یابد. به طور کلی میانگین بارندگی سالانه در این دو دوره تحت سه سناریوی انتشار، کاهش نشان داد. حداکثر مقدار کاهش در دوره آتی دور بود. علاوه بر این، رواناب دو دوره آتی نیز در اغلب سال ها کاهش نشان می دهد. پرونده مقاله