Large Amplitude Free Vibration Analysis of Axially Functionally Graded Plates

Author(s):  
Saurabh Kumar ◽  
Haraprasad Roy ◽  
Anirban Mitra

Large amplitude free vibration problem of axially functionally graded plates under the action of uniformly distributed load is analyzed using energy method. A variational approach has been applied for the generation of governing differential equations. A two part solution procedure has been adopted, where the static solution is sought in the first part and the dynamic problem is taken up subsequently as a standard Eigen-value problem. The governing differential equations for the static analysis are derived from the principle of minimum total potential energy whereas Hamilton’s principle is used for developing the governing equations for the dynamic analysis. Start functions for the analysis are chosen by satisfying the flexural and membrane boundary conditions and Gram-Schmidt orthogonalization procedure is used for developing the higher order functions. The dynamic behavior is presented as backbone curves in non-dimensional frequency amplitude plane. Mode shape plots for linear and non-linear frequencies are given to show the effect of vibration amplitude on dynamic behavior. The results are compared with the works of other researchers which confirms the accuracy of the present research work.

2016 ◽  
Vol 08 (06) ◽  
pp. 1650079 ◽  
Author(s):  
Salvatore Brischetto

The present work investigates the effects of the curvature terms in the three-dimensional (3D) equilibrium equations used for the free vibration analysis of functionally graded material (FGM) structures. The 3D equilibrium equations have been written in general orthogonal curvilinear coordinates which are valid for spherical shells. They automatically degenerate in those for cylindrical shells and plates considering one of the two radii of curvature and both radii of curvature equal to infinite, respectively. The approximation of curvature terms in the 3D equilibrium equations has been evaluated by means of frequency analyses. Results obtained via 3D equilibrium equations with exact geometry have been compared with those calculated via 3D equilibrium equations written with the approximation of the curvature terms. The effects of the curvature approximations depend on the thickness and curvature of the structures, on the materials, lamination sequences and FGM laws, on the frequency orders and vibration modes. The resulting system of second order partial differential equations has been reduced into a system of first order partial differential equations redoubling the variables. Therefore, the exponential matrix method has been employed using a layer wise approach. The final 3D equations have been solved in exact form considering harmonic displacement components and simply supported structures. The approximation of the curvature terms has been introduced in the 3D equilibrium shell equations. For numerical reasons, interlaminar continuity conditions and the top and bottom boundary and loading conditions have been written including the exact geometry. The introduction of curvature approximations only in the equilibrium equations is sufficient to obtain an exhaustive qualitative analysis of the importance of curvature terms in the free vibration problems for FGM structures.


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