Modal analysis of perforated rectangular plates in contact with water

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