Research Of Dynamic Response Characteristics On Ship Liquid-Filled Side Structure Under Impact Loads

The current shipping industry gradually comes to prosperity promoted by the development of global trade.As a result,the routes have become crowded with the continuous increase of tonnage,quantity and speed of transport ships,which increase the possibility of ship collisions.The ship collision accidents not only result in huge losses of lives and economy,but also the marine environmental damages.Hence,there are urgent demands to improve the crashworthiness of ship structures.Double hull structures are commonly used in civil transport ships to reduce structural damages and environmental pollution caused by collision accidents.During the ship collisions,large amount of ballast water between double shells can be used to absorb and disperse energy to protect the side structures of ships.In this thesis,the experimental scheme and numerical simulation are both carried out to analyze the dynamic response of the liquid-filled side structures under impact loads.In addition,the effects of top plate thickness and impact velocity are investigated in numerical simulations.The main research contents are summarized as following:(1)The generally approved theory and analysis methods for the ship collisions are reviewed and the relevant key technologies of numerical simulations have been summarized based on the non-linear finite element theory.(2)Based on the simplified collision model,the experimental scheme is implemented for analyzing the dynamic response of typical liquid-filled side structures.The experimental study is carried out to investigate the effects of the structural crashworthiness involving different top plate thickness,impact velocity and two extreme conditions on liquid-filling,which obtains valuable data for the acceleration of conical ram,structural deformation and pressure induced by the shock wave.From the experimental results,it shows that the liquid plays a good function of buffer and protection to plates during the collision.(3)Furthermore,the non-linear finite element software LS-DYNA is used to perform the numerical simulation for collision process of liquid-filled side structures.In the simulation,the contact and fluid-structure coupling are both considered in the collision model to analyze dynamic response of liquid-filled structures under different liquid-filled conditions.The accuracy of the numerical simulation method is verified by the comparison of the experimental and numerical results.(4)Finally,parameter studies are carried out by the numerical simulation method for the collision process of liquid-filled side structures,including the top plate thickness,liquid tank width,and quality of conical ram,impact velocity and stiffener type.As a result,the general laws on the structural dynamic responses are concluded based on the analyses of structural deformation,energy conversion,rebound velocity of ram and shock wave pressure under various load conditions.Therefore,an effective method to improve the crashworthiness of side structure is proposed,the ship liquid-filled side structure is optimized accordingly.