Dynamic response of a ring-stiffened underwater vehicle to a far-field underwater explosion

Thin-walled ring-stiffened cylindrical structures are widely used in underwater vehicles for their high efficiency and robustness. This study establishes a coupled acoustic-structure model to simulate transient fluid-structure interaction under far-field UNDEX loading, considering both stationary and cruising conditions. Parametric analyses evaluate the effects of standoff distance, cruising velocity, and detonation position on stress, displacement, and internal equipment response. Results show that cruising significantly lowers overall stress and alters displacement patterns, mainly due to dynamic unloading. Although stress distributions are generally similar for different detonation positions, displacements differ markedly because of bubble pulsation loading. Using the Shock Response Spectrum (SRS) method, the study further shows that, for a 30 kg TNT charge at 15 m standoff, accelerations in the guidance and motor sections exceed BV043/85 failure thresholds, implying potential equipment functional loss even without visible structural damage. The results support shock-resistant design and underwater shock assessment.