Investigation on the underwater explosion coupled loads testing technique and deformation response of thin plate subjected to underwater shock and fragments

The safety of ship structures under underwater explosions depends on their stiffness and strength. The coupled loads of underwater shock waves and fragments can cause severe deformation and damage to the structures. To accurately assess this situation, a novel underwater shock wave and fragment coupled load testing system (SF-CLTS) has been developed by modifying the gas gun system. By controlling the time difference of the launching system as well as the velocities of the flyer and bullet, the time interval of the coupled loads can be adjusted. The deformation process of the target plate can be visualized using the 3D digital image correlation (3D-DIC) method combined with images captured by high-speed cameras. The dynamic deformation and damage of aluminum alloy plates under the aforementioned loads were studied by means of SF-CLTS. Meanwhile, the theoretical analysis of the impact process between the thin plate and the fluid was carried out using the energy method and the plastic hinge-spring model, with supplementary and comparative analysis using experimental data. This revealed the correlation between structural deformation and the intensity of external shock waves (peak pressure and exponential decay time). This method is crucial for the safety assessment and design of ship structures, and helps to deepen our understanding of the complex impact effects of underwater explosions.