Symmetry breaking and vibrational mode localization in a circular cylindrical shell: Modeling and experiments

Vibration localization and eigenvalue loci veering in thin circular cylindrical shells are imperfection-sensitive modal phenomena that have been studied mainly through analytical and numerical models, while experimental evidence at the mode-shape level remains limited because thin shells exhibit high modal density, closely spaced circumferential mode pairs, and strong sensitivity to small geometric deviations. In this study, vibration localization in a thin circular cylindrical shell is investigated through a combined full-field experimental, numerical, and analytical approach. High-resolution measurements are obtained using a three-dimensional scanning laser Doppler vibrometer, enabling direct visualization of localized mode shapes and eigenfrequency splitting in the tested shell. Among the first twenty experimentally identified modes, four are found to be strongly localized, arising from the interaction of the ( m = 2, n = 6) and ( m = 2, n = 7) mode families. To interpret these observations, two complementary models are employed. The finite element model incorporates the measured three-dimensional geometry of the shell together with the boundary rims and reproduces the experimental mode shapes with very good agreement. By contrast, the analytical model is intentionally simplified and is not intended to reproduce the experiments quantitatively; instead, it is used to isolate and clarify the mechanism by which symmetry breaking gives rise to eigenfrequency splitting, mode veering, and localization. Taken together, the results provide both direct experimental evidence and a physical interpretation of imperfection-induced vibration localization in a realistic cylindrical shell.