High order finite elements in free vibrations of thick plates

The aim of this paper is to study the dynamic behavior of plates through the Reissner-Mindlin's theory, making use of the Finite Elements Technique to solve the displacement equation of plates in free vibration. The finite element adopted is the Lagrangean quadrangular of sixteen nodes (QL-16). In the first numerical example the criterion of Hinton and Huang's (1986) for discretization of circular plates is applied. In order to reproduce experimental results obtained by Pedroso (1983,1986), with a circular plate of steel and another of rubber both fixed with bolts, different boundary conditions are tested. In the second numerical example, the same discretization criterion is used for elliptical plates with different eccentricities. This time the finite element QL-16 is tested in several deformed shapes in order to observe the behavior of the solution. (authors)