Forced Vibration Numerical Analysis of Rectangular Elastic Orthotropic Damped Inclined Mindlin Plate Using Finite Difference Algorithm

Plates vibrate when load moves on them. In this paper, the dynamic response of Mindlin plate analytical model was converted to its numerical form using finite difference algorithm. The numerical model was analysed to ascertain the critical parameters contributing to the deflection of Mindlin plate under a moving load. The examination was more reasonable as in the likelihood of the plate laying on a Pasternak foundation was put into thought. Likewise the impact of damping was not dismissed. The plate considered in this paper was an inclined Mindlin plate, where the impacts of shear deformation and rotatory inertia were considered. The numerical equations were solved with the help of a developed computer program and Matlab. The results were consistent with what we have in the literature. The effects of the Pasternak foundation, damping, angle of inclination, and the moving load to the dynamic response of the elastic plate were exceptionally self-evident.


Introduction
The importance of moving load problem manifested in numerous applications in the area of Mathematics and Engineering.Structural elements are usually designed to support moving loads.Various authors have analysed the dynamic The definitions for moments along x and y axes, twisting moment and shear deformation along x and y axes are given as follows respectively [17] [18] [19] ( ) where, ( ) ( ) , , W x y T is the traversed displacement of the plate at time T.
( ) sin g θ = acceleration due to gravity of the load down the inclined plane.θ = angle of inclination of the plate to the horizontal.γ = damping coefficient.
( ) cos g θ = acceleration due to gravity of the load equal and opposite the normal force to the plane.
F S is the force of sliding friction.g is acceleration due to gravity.K, G 1 = foundation stiffness.
x y H(x) is the Heaviside function defined as: ( ) U is the velocity of a load of rectangular dimension ε by μ with one of its line of symmetry moving along Y = Y 1 .
A µε = , the area of the load in contact with the plate.
The plate is L x by L y in dimensions and h and h 1 are thickness of the plate and load respectively.ρ and ρ L are the densities of the plate and load respectively.G is the modulus of the plate.D is the flexural rigidity of the plate defined by ( ) ( ) k 2 is the shear correction factor.ν is the poisson's ratio of the plate.g is the acceleration due to gravity.E is Young modulus of Elasticity.M L is mass of the load.

Boundary and Initial Conditions
For a complete formulation of the problem, a simply supported rectangular Mindlin plate is considered as an illustrative example.If the edge y = 0 of the simply supported, it then follows that the deflection W along this edge must be zero.At the same time this edge can rotate freely with respect to the x-axis, i.e., there are no bending (M x ) along this edge.Therefore the boundary conditions can be stated as follows: [19] [20] [ for 0 and The corresponding initial conditions are

First Order PDE Version of the Governing Equations
The first order partial differential equations versions of the system of Equations ( 1)-( 8) are as follows: ( ) ( ) where , , 1 2 , where W is the deflection

Finite Difference Algorithm for the Model
Equations ( 16)-(26) were solved using a numerical method based on the finite difference algorithm.These equations were transformed into their equivalent algebraic forms.The finite difference definition of first order partial derivative of a function

( )
, , E x y t say, with respect to x, y and t respectively are as follows [21] [22]: where E is the function value of the centre of a grid, which is well approximated by the average of its values at the grid nodes [22].
Using the above finite difference definition on Equations ( 16)-(26) gives: ψ ψ ψ ψ ψ ψ ψ ψ ν ψ ψ ψ ψ ψ ψ ψ ψ The set of algebraic equations to be solved may be written in matrix form as: , 1 where N and M are the number of the modal points along xand y-axes respectively, Z k is a matrix representing the right half of Equations ( 16)-( 26) defined by The terms of the above Equations ((42) and ( 43)) can be represented in matrix form as follows: ,

Results Discussion
The paper set out to analyse, numerically, the vibration of rectangular elastic orthotropic damped inclined Mindlin plate, because of applied force, using finite difference method.

Conclusion
The in the x and y directions respectively.
The plate was supported by a Pasternak foundation.Deflection of the plate was calculated for specific values of foundation parameter and contact area of the plate.It was observed that Mindlin plate has highest maximum amplitude when compared with Non-Mindlin plate.The response maximum amplitude decreases with an increase in the value of the subgrade's shear modulus for fixed value of foundation stiffness, contact area and velocity.It was noticed that the response amplitude of the plate continuously supported M. C. Agarana, A. I. Ehigbochie DOI: 10.4236/am.2018.96043631 Applied Mathematics by a Pasternak foundation is less than that of the plate not resting on any elastic subgrade.As the foundation stiffness and shear modulus increase the response amplitude decreases.Also, it was observed that as the contact area increases the response maximum amplitude increases with fixed values of the foundation stiffness and the subgrade's shear modulus.Finally it was observed that the maximum amplitude increases as the velocity increases.
structure of interest was an inclined Mindlin rectangular plate on Pasternak elastic foundation, under the influence of a uniform partially distributed moving load.The problem was to use finite difference technique to solve the governing equation of a moving load problem.The dynamic response of the whole system was determined by solving the resulting first order coupled partial differential equations obtained from governing equations for the simply supported Mindlin plate.The study has contributed to scientific knowledge by showing that Pasternak foundation, on which the inclined Mindlin plate rests, has a significance effect on the dynamic response of the plate to a partially distributed moving load.The effect of rotating inertia and shear deformation on the dynamic response of the inclined Mindlin plate to the moving load gives more realistic results for practical application, especially when such inclined plate is supported by a Pasternak type of subgrade foundation. )