Modal analysis of perforated rectangular plates in contact with water

This paper presents an experimental modal analysis of perforated rectangular plates in air or<br />in contact with water. The penetration of holes in the plates had a triangular pattern with P/D (pitch to<br />diameter) 2.125, 2.500, 3.000 and 3.750. The plate was clamped along the plate edges by a number of<br />bolts and nuts. The natural frequencies of the perforated plates in air were obtained by the analytical<br />method based on the relation between the reference kinetic and maximum potential energies and<br />compared with the experimental results. Good agreement between the results was found for the natural<br />frequencies of the perforated plates in air. Additionally, it was empirically found that the natural<br />frequencies of the perforated plate in air increase with an increase of P/D, on the other hand, the natural<br />frequencies of the perforated plate in contact with water decrease with an increase of P/D.