Ship Structure Underwater Near-field Explosion And Residual Strength Reliability Analysis

Risks of modern warships which will be attacked at close range areincreasing recently. In order to protect the vessels from the risk, newnavel structural forms and large-scale structure of the ship are alsoemerging. Underwater near field explosion is a complex process. In orderto improve the ship’s protection capacity, the study of near fieldunderwater explosions and the new structure anti-explosion capacity arebecoming increasingly urgent.The research content of this paper includes a method consideringboth the shock wave and jet load and the dynamic response of underwaternear-field explosions of new navel structural forms. And the reliability ofresidual strength is also concerned.Firstly, the numerical simulation of near-field underwater explosionbubble motion process is being carried out to establish the jet impactmodel, and then the jet load is simplified according to theprincipleofconservationofenergy.Jet load is automatically added to thefluid-structure coupling simulation model after the shock wave phase toform a complete calculation process of the underwater near-field explosion process. In the calculation process, the subroutine of theMSC.Dytran software records the size of the damaged area statistics todetermine the extent of structural damage region. And then the influenceof explosion distance and the influence of the bulkhead in differentconditions are taken into account. These numerical examples validate thefeasibility of the method.The finite element method is carried to calculate the residualstrength of the damaged structure by using the ABAQUS software. Andthe effect of structural damage in ultimate strength analyses is concerned.The residual strength is treated as a variable data associated with yieldstrength and steel thickness. The statistical characteristic of the residualstrength is calculated by Rosenblueth method. By using the SESAM/Wadam software, the new large-scale ship hydrodynamic response iscalculated. The statistics of still water bending moment and wave bendingmoment are calculated by using the reliability method. Finally, theresidual strength of damaged ship structure reliability is calculated by theimproved first-order second moment method. The result is compared withthe target reliability index and it proves that the Y-type double shellstructure is excellent in anti-explosion.