Numerical Simulation Study Of Structural Protection Under Near-Field Underwater Explosion Loading

With the continuous development of torpedo technology,the possibility of ships and submarines encountering near-field underwater explosions has greatly increased,requiring the selection of suitable protection methods to improve their battlefield survival rates.Mitigating underwater explosion loading on ships and submarines is the main research direction for structural protection,which can be done by using shields for energy absorption and shock absorption.However,the current numerical simulation of structural protection only considers the influence of shock wave load,ignoring the damage caused by bubble pulsation and jet load in near-field underwater explosion.Therefore,more reasonable numerical methods are needed to increase the reliability of simulation results of structural protection.In this paper,numerical simulation is used to simulate the whole process of free-field and near-field underwater explosion,and the numerical simulation study of structural protection under near-field underwater explosion load is carried out as follows.Firstly,based on the Coupled Eulerian-Lagrangian(CEL)method in the numerical simulation software ABAQUS,the real explosive detonation model and the JWL state equation are used to simulate the volume and shape changes of free-field explosion bubble,and the accuracy of the Eulerian method is verified by comparison with experiment.After that,the simulation results of the bubble pulsation stage of explosive explosion between rigid plates are compared with the experimental results to verify the reliability of the CEL method.Secondly,the near-field underwater explosion can cause serious local damage to the hull.The protective shield composed of rubber-coated polyurethane affixed to the outer surface of the hull can effectively attenuate the impact load generated by the explosion.In this chapter,the finite element model is constructed based on an experiment to simulate the damping effect of the protective shield on the circular plate under the shock wave load.The effects of different structural parameters on the protective characteristics of the protective shield are explored,and finally,the impact resistance of the protective shield under bubble pulsation and jet loading is verified.Then,based on the previous paper,the outer layer of the protective shield is lined with high-strength composite material(GFRP)based on stealth and corrosion resistance considerations.The sandwich cylindrical shell structure of three materials,GFRP-polyurethane-steel,was loaded with shock wave loads.The damage,energy absorption and displacement results of the structure are analyzed by varying the parameters of burst distance,charge and thickness ratio,and the resistance to deformation and energy dissipation capacity of the structure are studied under bubble pulsation and jet loading.Finally,for the high-speed impact damage caused by bubble jets,it is not enough to rely on protective shields alone.In this chapter,we propose the use of "out-of-phase bubble" for structural protection,that is,the use of explosives to generate bubbles to change the direction of the attacking bubble jet to protect the structure.Through the numerical simulation of near-field dual explosive explosion in the water tank model,the interaction mechanism of underwater explosion bubble pairs is analyzed,and the feasibility of "out-of-phase bubble protection" is verified,which provides a new solution for the protection of high-speed water jets towards the structure.