Research On The Impact Response Characteristics Of Ship Cabin Based On Dynamic Substructure Method

The finite element numerical simulation and the real ship underwater explosion test are the main means of predicting the impact environment of the ship.The real ship test consumes a lot of human resources and financial resources and is greatly disturbed by the experimental environment,and is not repeatable.The development of modern computer technology makes it possible to simulate the large complex structure of ship by finite element numerical simulation.However,in the process of local refinement,the modification of local parameters is still required to simulate the whole structure.A large number of computing resources and time costs are still consumed in the process of simulation.Therefore,in order to ensure the accuracy of numerical simulation and reduce the computation cost,the purpose of this paper is to provide a substructure based method for ship structure modal analysis and impact environment prediction.The specific contents are as follows:First of all,the reliability of the finite element numerical simulation in forecasting impact environment of a ship is verified by underwater explosion test of a large floating impact platform.In the process of real ship test,the environment and sensor factors introduce zero drift error so The EMD method is used to process the impulse response signal.The improved EMD method is used to improve the endpoint effect of the traditional EMD method.The error between the finite element numerical simulation method and the real ship explosion test is analyzed.Secondly,characteristics of the low-frequency impact environment of floating impact platforms and underwater reinforced cylindrical shells are analyzed.The contribution of the overall structure to the impact environment of the ship structure is quantified.By analyzing the difference of the impact environment between the sub structure and the whole structure of the underwater reinforced cylindrical shell,the feasibility of predicting the overall impact environment by the substructure of the module is studied.The necessary conditions for the impact environment forecast of the sub structure are put forward.By adjusting the boundary conditions of cabin sub-structure,the accuracy of impact environment prediction by the model of cabin sub-structure is improved.Thirdly,the free-form modal synthesis technique is used to solve the modal information of underwater stiffened cylindrical shell structure.In this paper,the process of neutron structure freedom condensation is analyzed and verified through the structure of the module,and analyze the factors that affect accuracy and efficiency.The synthesis matrix of different number of compartments in complex connection mode is derived.Finally,the response signal is calculated by the free interface mode synthesis method which is realized by the central difference method.The application of central difference method analyzed from the aspects of computational efficiency,accuracy and convergence.In this paper,the dynamic substructure method based on the free interface modal synthesis technique is used to predict the impact environment of stiffened cylindrical shells under underwater explosion load.