Study On Damage Characteristics Of Sandwich Plate Structure Under The Combined Action Of Explosion Shock Wave And Randomly Distributed Fragments

Large surface ships are an important support for naval ocean-going operations and maritime power projection.With the rapid development of modern anti-ship weapons,such as torpedoes,anti-ship missiles and precision-guided missiles,it poses a serious threat to their survival and combat capabilities.Traditional grillage structure often has relatively limited anti-explosion impact ability,and sandwich plate,as a new type of protective structure,provides a new direction for improving ship protection ability.The load generated by the actual warhead explosion includes not only the high-intensity shock wave,but also the fragment group load with completely random shape,size and distribution formed by the shell crushing.There is a complex coupling effect between the two.Therefore,it is necessary to consider the combined effect of shock wave and fragments when evaluating the anti-explosion performance of sandwich plates.In this thesis,according to the general idea of “load-characteristics-response-protection,” the key problems such as the combined load characteristics of shock wave and fragment,the random distribution of fragment group and the dynamic response of sandwich plate structure under combined load are studied by combining experimental and numerical simulation methods.The relevant research results can provide technical support for the application of the structure in the field of ship engineering.The main work of this thesis is as follows:(1)The application research status of metal sandwich structure in the field of ship engineering at home and abroad is summarized.The research results of sandwich plate damage under the combined action of shock wave and fragment are summarized,and the research significance and main research contents of the thesis are clarified.(2)The generation,propagation,reflection and other load characteristics of explosion shock wave are introduced.The generation process and mass distribution characteristics of fragments are clarified,which provides theoretical support for subsequent experiments and simulations.(3)The finite element software LS-DYNA was used to carry out numerical simulation research on it,and the simulation results were compared with the experimental results to verify the effectiveness of the finite element technology.On this basis,the damage mode and energy absorption characteristics of sandwich plate under the combined action of shock wave and fragment are studied by combining simulation analysis technology and considering the uniform preset of fragments.The influence of detonation distance and panel thickness configuration on the damage deformation mode of sandwich plate is discussed.(4)Based on the characteristics of fragment mass distribution,the number distribution of fragments after the actual warhead shell rupture is predicted and transformed into the probability density function of the area distribution.Based on the Voronoi segmentation algorithm and Python programming,the power-law distribution random number generation module,the fragment area statistics module and the polygon circumcircle module are customized,and the main program is embedded to call.The parametric tool Grasshopper is used to establish a random distribution model of the fragment field whose area conforms to the power-law distribution.The genetic algorithm and Kangaroo point collision detection algorithm are used to optimize and correct the distribution model.(5)Based on the random distribution model of fragment field established above,the simulation model of sandwich plate under combined action is established when considering different distribution forms or different numbers of fragments.The coupling process of shock wave and fragment is analyzed.The blast resistance of sandwich plates with different structural forms is studied by changing the arrangement of core layer.