Shock Response Spectrum And Nonlinear Dynamic Analysis Of Underwater Vehicle

Underwater vehicle is a key part of China's military strategy system.The underwater environment is extremely uncertain,which puts forward quite strict requirements for launch of vehicles.The load of underwater vehicle is the input condition of vehicle structure design,which plays a key role in the design for lightweight structure and long-distance attack.At the launching stage,the vehicle generates a huge transient response due to water pressure.At present,the linear model is adopted to calculate the overall response of the vehicle,without considering the influence of the nonlinear structure of the vehicle connection.While the time history analysis method can provide relatively accurate results with expensive conputational cost,which is not suitable for practical application.Aiming at these problems,this paper analyzes the shock response spectrum of the vehicle in the stage of crossing water surface,and introduces the hybrid mode method to perform dynamic design of the vehicle considering the nonlinear structure.The main research contents of this paper are as follows:1.Using the theory of shock response spectrum,the shock response analysis of the equivalent linear model of underwater vehicle was carried out.Considering the influence of the randomness of underwater navigation on the load,the envelope spectrum of the shock response of underwater vehicle was obtained.Aiming at the shortcomings of shock spectrum,the dynamic response coefficient spectrum was proposed with more extensive application and more accurate results,its envelope spectrum was also obtained with randomness considered.This method can synthesize the response quickly in the frequency domain and get the modal synthesis response solution which is consistent with the time history analysis results.The advantages and disadvantages of various modal synthesis methods were compared.2.Aiming at the limitation of applying modal superposition method to linear model,a modal superposition analysis method for nonlinear underwater vehicle model was established based on the theory of hybrid modes.The analytic expression of the description functions of the tension and compression nonlinear elements were derived.The accuracy of the hybrid mode method was verified by researching the modal participation factor of the ultimate state.The modal superposition method of tension-compression nonlinear model was implemented within the allowable error range.3?Based on the hybrid mode superposition method,the dynamic design of underwater vehicle was performed,and the shock spectrum system of nonlinear structure of underwater vehicle was established.Firstly,the physical significance of the tension-compression nonlinear parameters in the hybrid modal theory was explored.Considering the influence of nonlinear parameters on the response of the structure,the dynamic design of the structure was conducted,and the influences of nonlinear parameters on the structural response were clarified.Then,based on the hybrid mode method and the shock spectrum theory,the shock response spectrum and dynamic response coefficient spectrum of the vehicle by modal synthesis of the nonlinear model were obtained.Compared with the linear model spectrum method,the synthetic response solution was more accurate.Thus,a nonlinear response method for the underwater vehicle with high accuracy and efficiency was established.