Research On Strength Of Ship Structures Subjected To Non-contact Underwater Explosion

The strength of ship structures subjected to underwater explosionis a main part of ship survivability. Underwater explosion could generate dynamic response over all ship,even break the ship hull girder, which may cause longitudinal strength problem. Also, explosion shock wave couldyield plastic deformation in local structures, such as ship bottom and broadside, which influences ship local strength. The strength researches of warship structure subjected to UNDEX have attracted much attention of navy in many countries. In our country, with the demand of ship anti-shock performance becoming higher, many related researches had been carried out. But they are not practical enough for ship anti-shock designing. So it is necessary to conduct deep study on the structure design to resistance underwater explosion shocks. Based on the coupled acoustic-structural method in ABAUQS, the researches of shiplongitudinal strength and local strength in the cabin are carried out, which could provide reference for protective performance design of ship structures.In this paper main works are as follows:(1) The coupled acoustic-structural method in ABAUQS is introduced and verified by two examples. After discussion about calculation methods of underwater explosion problem, the theory and boundary conditions of coupled acoustic-structural method arededuced in detail.According to theoretical resolution and experiment data, the accuracy of ABAQUS is verified;(2) The numerical model of whole ship is built. The model includes all decks, superstructure, shell plate, deck grillage, ect. Water model with proper size is also built. The wet modal calculation results indicate that the low-order frequencies of ship hull girder have low error respected to experimental estimation, which validates the numerical model;(3) Researches on longitudinal strength of ship subjected to underwater explosion are conducted. The whole detailed ship model and simplified hull girder model are calculated under typical underwater explosion conditions. The equivalent plastic strain of typical sections in detailed ship model is checked. The explosion bending moment curves, hogging and sagging maximum explosion bending moments are compared between two models. Results show that the simplified model has good accuracy in calculation of explosion bending moment, which could provide reference for estimating of explosive bending moment;(4) Researches on local strength of ship cabins subjected to underwater explosion are conducted. Three-cabin model is built and verified according to whole detailed ship model to analyze local strength of cabin subjected to underwater explosion. Numerical simulations of cabins which have different bottom plate thickness, main frame numbers, bottom keel numbers are carried out. The influences in changing design parameter are summarized in three aspects: plastic deformation, maximum dynamic mises stress and maximum acceleration, which could provide reference for anti-explosion designing of ship cabin structures.