Interaction of Localized Defects in Buckling of Axially Compressed Cylindrical Shells

Abstract Geometric imperfections are the primary cause of the pronounced reduction in the buckling load of cylindrical shells subjected to axial compression. Localized defects, which are commonly introduced during manufacturing, are particularly prevalent. This study investigates how interactions between such localized defects affect the critical buckling load of cylindrical shells through high-fidelity finite element simulations. We first quantify the influence of defect amplitude on the knockdown factor for cylinders with various radius-to-thickness ratios containing a single defect. The results show that the knockdown factor decreases with increasing defect amplitude and gradually approaches a threshold value. We then examine the buckling behavior of shells containing two identical defects. The results reveal that the knockdown factor varies nonmonotonically with increasing spacing between the defects. To identify the relative location beyond which defect interaction vanishes, we introduce a new definition of defect spacing such that the minimum threshold spacing for noninteracting defects is independent of the defect width. The simulations further demonstrate how the relative orientation of the defects, measured by the inclination angle, affects the threshold spacing. Finally, we consider shells containing two defects of different amplitudes. It is shown that the qualitative behavior of the relationship between the knockdown factor and defect spacing is strongly affected by the ratio of defect amplitudes. When the defects are sufficiently far apart, the buckling load of the shell is determined entirely by the defect with the larger amplitude.