Research On Impact Resistance Of Truss Box Floating Raft Subjected To Underwater Explosion Load

With the threat of underwater non-contact explosion becoming more and more serious,the living environment of underwater vehicle are getting worse.As an effective vibration isolation method,floating raft has been widely used in underwater vehicles.At present,the research of floating raft structure is focused on its vibration isolation effect,but there is little research on its shock environment and the shock protection of its equipments and personnels.The limited internal space and better maneuverability of underwater vehicles require the floating raft to have higher space utilization ratio and lower weight.As an auxiliary means of model test,the accuracy of numerical simulation depends on the consistency of the numerical model and the experimental model in the target characteristics.It is necessary to update the numerical model according to the test data.Aiming at the above problems,this paper studies the impact resistance characteristics of the floating raft system in the underwater vehicles subjected to underwater explosion load.The contents are as follows:Firstly,the theory of underwater explosion and shock environment was studied,and the formation and propagation of shock wave and bubble pulsation were introduced.The calculation method of underwater explosion load was studied,and the calculation principle of shock spectrum was expounded.The dynamic modeling methods of floating raft system were studied,and the advantages and limitations of different methods were introduced.The dynamic model of floating raft anti-impact system was established by using multi rigid body method and substructure method.Secondly,based on the development trend and demand of large-scale floating raft and thewhole-cabin floating raft,taking into account weight,the anti-impact strength,space utilization ratio and impact protection performance,a kind of truss box floating raft was designed.The equivalent stiffness and space utilization ratio of different floating raft structures were calculated.The finite element model of the floating raft system was established and its antiimpact strength was checked.The shock environment on platforms of different floating rafts under underwater explosion load was calculated,and their shock protection performance for equipments and personnels were compared.Considering shock protection performance and space utilization ratio,the optimal configuration of floating raft was determined for further analysis and research.Thirdly,the impact resistance of the floating raft was studied.The effects of shock absorbers and raft frame on the shock response of floating raft were studied.Then the shock environment distribution characteristics of floating raft platforms were studied,and the shock environment of the front and back blasting side of floating raft were compared.The effects of stiffness,number and damping of the floating raft shock absorbers on the shock environment of floating raft platforms were studied.It provides a reference for improving the impact resistance and shock protection performance of floating raft.Finally,the finite element model of the floating raft was updated based on the parametric method.The finite element model updating methods and multi-objective optimization algorithms were studied.The finite element model to be updated was introduced,and the sensitivity analysis of 37 parameters of the model was carried out.The parameters with high effect on shock environment of the target equipments were obtained.The NSGA-II genetic algorithm was studied,and the parameters of the finite element model were optimized and updated based on NSGA-II genetic algorithm.The result shows that NSGA-II genetic algorithm is very effective in solving the problems of multi-parameter updating and multi-objective optimization of finite element model.