Research On Characteristics Of Water-filled Structure Under Impact Condition

With the rapid development of the shipping and transportation industry,the density of ships on the route is increasing gradually,besides the ship has developed to large-scale and high speed model,which will raise the probability of the ship collision.Moreover,Ship collision can always make some disasters due to the large inertia,including the casualties,damages of the structures and pollutant leakage,of the ship.Therefore,it's important to study the collision mechanism of ships in order to improve the crashworthiness of the ship.Unlike the situation in collisions between other structures,there is a large amount of ballast water between the double shells and the protective water tank,which will interact with the hull structure during the collision process.In addition,these ballast water also play a part in the energy absorption of collisions,which will affect the results of the collision.In order to analyze the effect and mechanism of the ballast water under the impact load,in this paper,for two typical case(full of ballast water and none of ballast water),the performance of structures in collisions is studied by using experimental means combined with simulation analysis.The main content of this paper included.Firstly,in this paper,the research about the ship collision dedicated by domestic and foreign scholars are presented.Some key technologies in finite element numerical simulation of the ship collision are summarized as well.Secondly,collision experiments of the cylindrical tank structures are carried out.For two filling status,rounded plates of varied thickness are tested by hitting against conical ram under different impact velocity.The experiments data verifies the impact of the geometric parameters to the crashworthiness of structure by comparing of acceleration,deformation and pressure in different test.Thirdly,finite element numerical simulation analysis of all experimental models was covered,and the process to establish the finite element analysis models using the software ANSYS/LS-DYNA was introduced in detail,including the mesh size,element type,material model and the fluid-structure coupling.Comparing the results,for instance the stress and deformation results of the plates and pressure results,we can find that the ballast water between the double shells of the ship can reduce the deformation of the outer plate effectively by decreasing energy absorption and transformation.And the protective effect is more obvious as the impact speed increase.Finally,the simulation results were compared with the test results,to verify the reliability of the finite element method.And base on that,the plates' thickness and the tank height were studied to verify the impact of the geometric parameters to the crashworthiness of structure.The results show that either increasing the thickness of the outer plate or reducing the thickness of the inner plate can improve the crashworthiness of the structure.And decreasing the height of the tank can make sense as well.