Modal localization in vibrations of circular cylindrical shells with geometric imperfections: Fid-Bau Portal

Modal localization in vibrations of circular cylindrical shells with geometric imperfections

Hemmatnezhad, M. / Iarriccio, G. / Zippo, A. / Pellicano, F.

Abstract The present study aims to investigate the effect of geometric imperfections in circular cylindrical shells on the vibration characteristics. Perfect circular shells are characterized by the presence of double shell-like modes, i.e., modes having the same frequency with modal shape shifted of a quarter of wave-length in the circumferential direction. However, in the presence of geometric imperfections, the double natural frequencies split into a pair of distinct frequencies, the splitting is proportional to the level of imperfection. In some cases, the imperfections cause an interesting phenomenon on the modal shapes, which present a strong localization in the circumferential direction. The present study has been carried out by means of a semi-analytical approach. Theoretical formulation were derived based on Sanders–Koiter thin shell theory. The analytical results have been compared with those of standard finite element analyses. The results corresponding to the analysis of modal localization are novel and can be used as a benchmark for further studies.

Highlights • The existence of modal localization is studied in continuous axisymmetric structures when the symmetry is suitably perturbed. • Modal localization in cylindrical shells with geometric imperfection is investigated. • The effects of geometric imperfection on the frequencies splitting and localization of mode shapes are examined. • The present method is capable of predicting the vibrational behavior of geometrically imperfect cylindrical shells. • Any geometric imperfection introduced to pairs of conjugate modes does not give rise to localization of modal shapes.