Research On The Damage Mechanism Of Multicamerate Defense Structure On Warship Broadside Subject To Underwater Contact Explosion

Underwater contact explosion is the most severe situation when a warship was attacked.The damage caused by underwater weapons will directly threaten the survivability of warship.Under normal conditions,underwater contact explosion includes shock waves,pulsating bubble,and high-speed fragments.It is difficult for conventional structures to defend these loads at the same time.After nearly a century development,at present,large warships usually deploy three-layer protection structures in the form of air-liquid-air on the broadside to accomplish comprehensive defense of these three loads at the same time.In this paper,the Arbitrary Euler-Lagrangian method(ALE)is used to study the underwater contact explosion load characteristics,the damage mode of simple frame structures,and the damage characteristics of multicamerate structures.Finally,completing the exploration of the protection mechanism of the multicamerate defense structureIn this paper,the user-defined equation of state in LS-DYNA is developed first,and obtaining the GRUNEISEN equation of state that can consider the cavitation effect.Then,the underwater explosion load was verified by the ALE method.The calculation results were compared with the Zamyshlyayev empirical formula of the shock wave,and the accuracy of the shock wave load simulated by the ALE method was verified.Then,according to the underwater contact explosion experiments in the literature,the corresponding finite element model is established.Through analyzing the break area and deformation of the plate,the accuracy of the method in the underwater contact explosion calculation was further verified.Based on the verification of the calculation method,research on underwater contact explosion load characteristics of near-elastoplastic structures was carried out in this paper.Firstly,based on the stress wave theory,the propagation characteristics of shock waves between multiphase media are derived.Then the pressure characteristics of the flow field,the media on both sides of the structure,and inside the tank are studied separately,obtaining the propagation law of shock wave between multiphase media.Then,the motion characteristics of the bubbles near the rigid wall,empty cabin,and the notched empty cabin,as well as the pressure characteristics in the cabin were studied.Finally,based on a simple plate underwater contact explosion model,the law of the maximum fragmentation speed and the scattering angle under different TNT charge and plate thicknesses are calculated.This conclusion can be used to initially estimate the structural fragmentation loadOn this basis,the paper studies the failure mechanism of the plate frame structure under the contact explosion loads.Firstly,the dynamic failure characteristics of marine steel were investigated.Then,the composite damage model of ductile metal under various damage mechanisms was used to study the failure modes of simple plates and stiffened plates under different impact loads.The plate frame structure deformation characteristics and the element stress state on the crack propagation path of the stiffened plates are analyzed under the different TNT charge and detonation distanceFinally,returning to the research of the protection mechanism of the multicamerate defense structure.Through designing a underwater contact explosion scale model test,the calculation method in this paper is further verified the from the break area and structural deformation.And through the propagation characteristics of shock wave in multicamerate defense structure,bubble load coupling characteristics with multicamerate defense structure,damage characteristics of frame structures,and structural energy absorption characteristics of the underwater contact explosion,the protection mechanism of multicamerate defense structure is revealed.