Circumferential Response Differences and Plastic Deformation Mechanisms of Ring-Stiffened Cylindrical Shells Subjected to Underwater Explosion Shock Waves

Ring-stiffened cylindrical shells are widely used as load-bearing components in submarine pressure-hull sections. Existing underwater explosion studies have mainly emphasized incident-face denting or global failure, leaving unresolved how circumferential shock-wave diffraction and internal structural load transfer produce different response sequences and plastic-strain accumulation at the incident, side, and rear faces. A mechanism-oriented underwater explosion model test was conducted using a 44 g TNT charge at a stand-off distance of 0.50 m, and a fluid–structure interaction model was established in MSC.Dytran using the general coupling method. The model incorporated the Cowper–Symonds strain-rate effect of 16MnR steel and was validated against the Cole empirical peak pressure and measured incident-face residual deformations. The calculated free-field peak pressure was 35.50 MPa, with an error of 0.65%, while the mean relative error of the six residual-deformation measurements was 13.50%. The shell plating between adjacent ring stiffeners exhibited higher velocity and acceleration peaks than the stiffeners, indicating the local constraint imposed by the ring stiffeners. The side-face nodes showed symmetric transverse expansion, and the corresponding elements exhibited no discernible equivalent plastic strain. The rear-face center displayed a delayed axial response, and its representative element reached a final equivalent plastic strain of approximately 1.32×10−3, compared with 0.40×10−3 for the incident-face element. These results identify distinct circumferential response modes and show that macroscopic motion amplitude is not simply correlated with local plastic deformation.