Research On Dynamic Response And Protective Structure Of Unmanned Craft Under Underwater Explosion Load

Since the 21 st century,with the rapid development of modern science and technology,the shipbuilding industry is also developing in the direction of modernization.Marine intelligent transportation has become an important part of the science and technology strategy of all countries in the world.Composite material unmanned boats have become an important part of maritime intelligent transportation due to their lightness,flexibility and performance superior to traditional materials.They are widely used to perform tasks such as peacekeeping,electronic warfare,scientific research and exploration,traffic command and search and rescue security.And other military or non-military missions.When the composite material unmanned boat performs missions in dangerous areas,the hull has a high probability of being sunk by anti-ship weapons such as torpedoes and mines.Moreover,due to the small size and weak overall structural rigidity of the composite material unmanned boat,once it is attacked by the above,The consequences are very serious.Based on the theoretical research of the near-field underwater non-contact explosion,this thesis studies the shock wave numerical simulation method of the underwater explosion in infinite waters,and obtains the propagation law of the underwater shock wave in the underwater explosion process,and compares the relevant empirical formulas and theories.The results are compared,the Eulerian fluid-structure coupling numerical simulation method is determined,and the composite unmanned boat is taken as the research object,combined with the transient nonlinear finite element software MSC.Dytran,which has no effect on the steel unmanned boat and composite materials.Numerical simulation study was conducted on the dynamic process of human boat subjected to near-field non-contact underwater explosion,and the damage form and damage characteristics of the composite material unmanned boat and steel unmanned boat hull structure after being subjected to underwater explosion loads were studied respectively;The influence of different composite material layup schemes on the anti-blast performance of the composite material unmanned boat is analyzed,and the structure and material optimization scheme of the composite material unmanned boat with better anti-blast performance is obtained.The main research work of this thesis is as follows:(1)Based on the theoretical research of near-field underwater non-contact explosion,the numerical simulation method of underwater explosion shock wave in infinite waters is studied.Under different Euler grid sizes,the underwater explosion shock wave is studied in infinite waters.Numerical simulation of the propagation process of the shock wave is carried out,and the propagation law of shock wave in the underwater explosion process is obtained.The simulation results and the actual software and hardware conditions are combined to determine the Euler domain fluid-solid coupling numerical simulation method with higher calculation accuracy.The simulation results are compared with related empirical formulas and theoretical results,which verifies the reliability of the calculation accuracy of the finite element model in this thesis,and provides a theoretical and technical basis for subsequent research;(2)Numerical simulation of the response process of the steel unmanned boat under the near-field underwater non-contact explosion load is carried out,and the dynamic response of the hull structure of the unmanned boat under the near-field non-contact underwater explosion load is obtained.The dynamic response characteristics of the hull structure deformation and the energy absorption of each part of the hull under different forms of near-field underwater non-contact explosion loads are analyzed separately,and then the hulls under different forms of underwater explosion loads are obtained.The destruction mode of the head-on section and the whole ship;(3)Research on the dynamic response of composite unmanned craft under underwater explosion load.Based on the numerical simulation results of the dynamic response of the composite material unmanned boat,the difference between the composite material and the steel material hull destruction process is studied,and the sensitive factors that have an impact on the anti-blast performance are obtained;(4)Research on protective structure performance.Four hull structure and material optimization schemes are proposed.Under the premise of keeping the total thickness of the main energy-absorbing structures such as the ship bottom and inner bottom plate unchanged,starting from the stress distribution,energy absorption,acceleration,etc.,the hull structure of the unmanned boat is analyzed.The dynamic response characteristics of the near-field underwater non-contact explosion load is carried out on the anti-explosive performance of the composite unmanned boat using the new structure,and the new protective structure with the greatest improvement in the anti-explosive performance of the unmanned boat is obtained.