Research On Assessment Method For Overall Damage Of Warship Subjected To Underwater Explosion

The shock resistance of warship structure, which is related to the vitality of battling warship, has being paid much attention by Naval in the world. Actual combat and prototype explosion testing indicated that the explosion bubble load can cause the one-time damage of warship with the hull ruptured. Almost all the countries'standards and assess methods are about shock wave and local damage, while the research on overall damage of the warship considering the action of the bubble is very rare, and can not meet the engineering demands. Therefore, the following research work is carried out in this paper.Employing the potential flow theory and modal superposition method, the whipping response of simplified elastic ship beam subjected to explosion bubble is studied theoretically. The effect of the length of ship beam on the deformation is investigated, and the argument is verified theoretically that the slender warship is induced to violent oscillatory motion by the explosion bubble easily.Aiming at the finite element model of entire ship, the shock wave pressure is gained by the Geers and Hunter model, then the response of ship in the shock wave stage is calculated using the coupled acoustic-structural method, the boundary element code and the nonlinear program for structure are combined to simulate the response of ship in the bubble stage. Applying the fast arithmetic, the computational efficiency is improved obviously. And then, comparing the results with the experimental data, the validity of the numerical method is proved.The damage characteristic of the ship structure under shock wave and bubble load is analyzed. The buckling failure mode of the brace and stringer plate and the whole damage pattern of ship hull caused by the whipping motion are researched emphatically. Then, the average Von Mises stress over the ship cross section, the amplitude of vibration of the whipping motion and PEEQ are studied. What's more, the influence laws of parameters e.g.depth of explosion, position angle on the overall response of warship are summarized.Based on the research on the overall response law and damage pattern of ship, the concept called"artificial wave"bending-moment is extracted, and the engineering prediction formula is generalized. Finally, taking the still water bending-moment and wave bending-moment into account synthetically, the evaluation method for warship overall damage is established, main work of which is estimating the"artificial wave"bending-moment.