Research On Performance Of Hull Structure Under Collision And Extrusion Load Of Ice

In recent years, with global climate getting warmer, a large number of glaciers in thenorth and south poles have been melting, it is entirely possible that ship could sail in thepathless seas like Arctic Ocean in the near future, thus shortening transport distance betweenAsian nations and Europe as well as Americas. At the same time, geological explorationfound that polar region is rich in oil and gas resources, the oil and gas exploitation plan ofhuman beings would also have preferred here, ports and waterways in the high latitudeswould usher unprecedented prosperity. However, no matter opening of channel or mining ofoil and gas, mankind could not avoid ice load related problems, which would increase theprobability of damage that ship and marine structure subjected to ice load, in the event ofthe accident such as damage of structure and leakage of oil and gas, would cause significantloss of life and property to the nation and its people.Based on the above reasons, research on performance of hull structure under collisionand extrusion load of ice has been carried out in this paper. Considering the coupling effectbetween solid and fluid, finite element simulation technology of ship—ice collision wasstudied, influence law of ship-ice collision parameters to collision between ship’s shoulderand iceberg(mass block) was discussed, changing ice floe collision parameters, collisionresponse of bow structure and ice floe was simulated, the extrusion ship subjected by icelayer was analyzed, aiming at ship damage, structure strengthen suggestion was proposed.Main works were as follows:（1）According to the elastic-plastic theory, material characteristics and failure criteriaabout ship steel was elaborated in the thesis，the latest method of numerical simulation aboutice was introduced, take iceberg as an object, material model and constitutive relation of icewas studied, based on Tsai-Wu yield surface, ice material parameters are demonstrated, referto previous rigid wall collision test of ice with cone shape, the pressure-area curve wasconsistent with foreign scholars’ experimental result and recommended curve by ISO/CD19906(2010), the effect of water was taken into consideration, its material model andequation of state were determined, specific methods within which to achieve fluid-solidinteraction analysis in LS-DYNA was illustrated, the feasibility of implementation offluid-solid interaction analysis by LS-DYNA was argued combined with the example;（2）Finite element models of ship, ice and water were established by pre-processing software PATRAN, on the premise of considering fluid-structure coupling effect, throughnonlinear finite element software LS-DYNA, kinds of cases about collision between ship’sshoulder and ice were calculated, the differences of hull structural response were studied,the response law and features of hull structural damage, collision force and energyabsorption were revealed considering ship-ice collision influencing factors such as shape oficebergs, collision position and speed of ships, flow field distribution of water under thecondition of ship-ice collision was briefly analyzed;（3）In high altitude waters, there was frozen ice or ice raft floating on the sea, in orderto pass through ice region, ship must squeeze and collide with it. Collision between bowstructure and ice floe was simulated, mainly considering the change of single collisionparameter such as ice thickness, motion state and physical property, structural responsedifferences on the aspects of damage, speed variation and collision force were studied, theresponse law about above factors to ship-ice collision was obtained;（4）The scenario that ship subjected to extrusion was analyzed and simplified in thepaper, focused on research of the calculation of ice layer’s temperature field and stress field,combined with the specific conditions and test data, the temperature field of each time stepis obtained using FEM software, with the method of subtraction towards temperature fieldof adjacent substeps, the stress distribution of corresponding state was acquired andaccumulated.Aft that,took a coastal cargo ship for example, built its FEM model of bow andstern(single hull),on the basis that ship-ice contact interface was assumed rigid, the stressfunction was fitted and loaded on hull model. The damage of ship structure was analyzedand structure strengthen suggestion was proposed according to the results of calculation.