Study On Repeated Collision Damage Of Hull Structure At Low Temperature

With the increasingly severe land energy situation and the increasing demand for resources by human beings,the polar regions with a large number of oil and gas resources to be exploited have become the hot spots of all countries.At the same time,global warming has accelerated the melting of polar glaciers,and further expanded the route range and navigation time in the polar regions,which has brought great convenience to polar scientific research,resource development and cargo transportation.However,the severe low temperature and ice load environment in polar regions pose a great threat to the safety of polar ships.Ships sailing in polar regions will inevitably collide with ice floes repeatedly,which will lead to the accumulation of deformation and damage of hull structure.Once the hull is damaged,it may cause disastrous consequences.The research on collision damage of polar ships can provide reference for the initial design of hull structure strength,and has important significance and value for ensuring the navigation safety of ships.At present,most of the research work at home and abroad mainly focuses on the single collision phenomenon of polar ships,and the research on the deformation and damage mechanism of polar ships under repeated loads is relatively few.Therefore,aiming at the damage problem of hull structure under repeated collision load in low temperature environment,this paper has carried out the following work contents:1)The numerical simulation technology and the mechanical properties of hull materials are studied.Firstly,the basic theory and key technologies of nonlinear finite element simulation are briefly introduced.Then,uniaxial tensile tests of EH36 steel at low temperature-40℃and normal temperature of 20℃are carried out to obtain the material stress-strain curves at different temperatures,which can provide reliable data for the material nonlinear input in the subsequent numerical simulation research,and explore the effect of low temperature on the mechanical properties of EH36 steel.2)The scaled models of typical hull members’ plates and stiffened plates were selected as the research objects,and the quasi-static monotonic loading and repeated loading tests of hull members were carried out at low temperature of-40℃ and normal temperature of 20℃.The LS-DYNA nonlinear finite element analysis software was used to carry out corresponding numerical simulation calculations to verify the reliability of the numerical simulation method and the numerical model of hull materials.Combined with the test and simulation results,the deformation mode and ultimate bearing capacity of plate and stiffened plate under local transverse load,and the damage accumulation mechanism under repeated load were explored,and the influence law of low temperature on the collision performance of hull components was revealed.3)The LS-DYNA nonlinear finite element analysis software is used to simulate the repeated collision between ship and sea ice at low temperature,Firstly,the main physical and mechanical properties of polar sea ice are studied,and the reliability of the numerical model of ice material is verified according to ISO recommended curves.Then,taking a polar icebreaker as the research object,two typical scenarios,namely,repeated collision of bow to break ice and multiple collision between bow and ice floes are selected to establish numerical model for simulation calculation.Based on the results of damage deformation,collision force and energy dissipation,the cumulative damage mechanism of ship structure under repeated collision load is analyzed.