Research On Warship Response Subjected To Underwater Explosion Considering Cavitation And Strain Rate Effect

As well as shock waves and bubble pulse loading,another effect,that is cavitation,a high reloading pressure is generated when the cavitated region closure,and the cavitation effect will have a greater impact on the response of structure.For metal materials,the mechanical properties are related to strain rate,and the constitutive relationship of materials is directly related to the accuracy of simulations such as underwater explosion.In order to accurately predict the deformation and damage modes of the warship structures subjected to the underwater explosion,it is particularly important to study the dynamic mechanical properties of marine steel and establish a constitutive model.Therefore,considering the effects of cavitation and strain rate,has a great significance to accurately evaluate the dynamic response of ship structures subjected to underwater explosion.The strain rate and cavitation effects on the impact response of near-surface marine structures was comprehensively studied.The constitutive model of the EH36 steel was obtained by using MTS tensile test and SHPB compression test.On this basis,several typical ship structures subjected to underwater explosion include the stiffen plate and warship section are numerical simulated,and the comparison between dynamic response of the structure considering the cavitation effect and not.The specific research contents are as following:(1)According to the Arons method,the cavitation region boundary formed by any equivalent of different types of charges at any depth is obtained,which provides a theoretical basis for the selection of the finite element model range of the water.The cavitation effect generated by the shock wave is simulated by the acoustic-structure algorithm.The calculation results and experimental results are in good agreement,and verify the accuracy of using this method to calculate cavitation effects.(2)The mechanical property of EH36 steel was tested using MTS material testing machine and SHPB equipment,and corresponding stress-strain curves under quasi-static strain rate and high strain rate were obtained,it was found that EH36 steel is strain rate sensitive material.Based on the Cowper-Symonds model,its viscous parameters and strain rate hardening parameters were fitted.Using the ABAQUS to simulate the experiment and compared with the experimental results to verify the accuracy of the constitutive model.(3)The stiffened plate of the typical position of the warship was selected as the research object,the dynamic response of the typical stiffened plate subjected to the underwater shock wave load is analyzed by the acoustic-structure algorithm.and the comparison between dynamic response of the structure considering the cavitation effect and not,response such as acceleration,velocity,displacement are presented.The shock wave propagation and water pressure changes in the water are analyzed,and the reloading pressure caused by cavitation effect on the stiffened plate are discussed.The result shows that the duration of reloading is several times longer than the duration of shock wave,and the acceleration peak caused by the reloading is even greater than that caused by the shock wave,the velocity decay time becomes slower,the action time of the load on the structure is increased,and the vertical displacement of the structure is obviously increased.(4)The finite element model of a typical warship section is established to study the dynamic response characteristics of the structure subjected to underwater explosion.The propagation of shock wave in water and the variation of cavitation area with time were discussed.The dynamic response of the structure at the typical position of the warship structure was compared under the two conditions of considering and not considering the cavitation effect.The results shows that the reloading caused by the collapse of the cavitation zone will have a greater impact on the response of the structure.Under the reloading,the vibration of the structure is more intense and the loading time is more longer.Under the basis of considering the cavitation effect,the time history curves of acceleration,velocity and displacement of the typical position of the warship section were obtained under the conditions of explosion at different depths and different side angles,the variation of the peak value of each response was also studied.