Abstract：The advancement of deep-sea exploration demands shell structures for underwater vehicles that combine high hydrostatic pressure resistance, effective low-frequency vibration/noise suppression, lightweight design, and compact layout. In this study, a novel helical cylindrical shell is proposed, which is constructed by a cylindrical grid sandwich structure with mathematically equation-driven Archimedean spiral slits in the inner panel. The vibration and noise reduction mechanisms are investigated via theoretical, numerical, and experimental methods. Flexural wave bandgaps of the cylindrical shell are computed via the finite element method (FEM), and the generation mechanism is revealed through the vibrational modes of the unit cell. Furthermore, the vibration transmissibility obtained from FEM and experiments verifies the results of the flexural wave bandgap. A theoretically sound absorption model based on the electro-acoustic analogy method and a finite element model are established to compute the sound absorption coefficient, followed the domenstration of the absorption mechanism. It can be found that the proposed shell achieves multifunctional integration with lightweight, high load-bearing, and broadband flexural wave/noise suppression capacities, while preserving the external geometry and internal space. Specifically, it can withstand 10 MPa hydrostatic pressure. Band structure analysis reveals two vibration bandgaps around 400-450 Hz, while vibration transmission tests show an average reduction of 10 dB across 1-2000 Hz. A peak absorption coefficient of 0.854 is achieved at 661 Hz, with an effective bandwidth (coefficient ≥0.5) of 290 Hz (540-830 Hz). In addition, structural-fluid coupled vibration transmissibility reveals that the first trough shifts to a higher frequency by 135 Hz in underwater conditions. The proposed shell overcomes the limitations of traditional cylindrical shells with single functionality. The integrated design method combining spiral and sandwich structures offers novel insights for multifunctional shell design in underwater vehicles, and presents broad application prospects in deep-sea equipment.
2026, Vol. 47 
