PARAMETRIC IDENTIFICATION OF CRITICAL LOCALIZED IMPERFECTIONS IN THE BUCKLING OF AXIALLY COMPRESSED CYLINDRICAL SHELLS

ABSTRACT: The buckling behavior of axially compressed cylindrical shells is extremely sensitive to localized geometric imperfections, which can significantly reduce the critical load. This study aims to identify the critical localized defect through a comprehensive parametric analysis based on nonlinear finite element simulations. The main parameters considered are the relative amplitude of the imperfection and its axial extent, whose influence on the critical load is systematically investigated. The results demonstrate that the reduction in critical load strongly depends on both parameters. In particular, the maximum decrease occurs for imperfections with an intermediate axial extent and a moderate-to-large amplitude, highlighting the complex sensitivity of buckling behavior to localized defects. For each amplitude level, a specific wavelength is identified that maximizes the destabilizing effect. The most critical configuration is obtained for an amplitude ratio A/t≈2.5 and a wavelength parameter α≈2–2.5, leading to a normalized critical stress of approximately σcr/σcl≈0.2, which corresponds to a reduction of about 80% compared to the classical theoretical prediction. The proposed parametric approach provides a reliable framework for identifying the most detrimental imperfection configurations. These findings are directly applicable to the design and optimization of thin-walled cylindrical structures under axial compression, contributing to improved safety and reduced risk of premature buckling. The study thus offers a rigorous methodology for characterizing critical imperfections and enhancing the structural performance of cylindrical shells.