Natural frequencies of perforated cylindrical shells

The vibration characteristics of cylindrical shells have been of great interest for many years due to their wide range of applications. This paper studies the effects of a homogeneous perforation pattern on the natural frequencies of cylindrical shells. The perforations were arranged in a square or triangular pattern with the pattern covering the entire surface area of the shell. All perforations were circular with each hole having the same radius. Finite element models were used to study the effects of the patterns. The number of holes in the pattern was varied between 25 and 825, while keeping the total mass (or area) removed from the cylinder constant. Shells with large and small length to radius ratios were modeled. It was found that as the number of holes increased, the natural frequencies approach a steady value. Graphs are presented showing the variation in natural frequencies as the number of perforations varies. Impact testing was used to experimentally verify the finite element results. Excellent correlation was found between the experimental and finite element data.