Analysis And Experiment Of Hydroelasto-plasticity Of A Ship’s Hull Girder

The carrying capacity of the hull beam structure is an important index for the international classification society to investigate the safety of ships,and the ultimate strength evaluation of the hull beam structure has always been regarded as a research hotspot in academia.When the ship encounters the limit sea condition,the hull beam collapses under the action of wave load,which is a dynamic nonlinear process.At the same time,there is a strong nonlinear coupling between the deformation of the hull beam and the wave load,and the change of the bearing capacity of the hull beam structure is closely related to the wave height and period.Therefore,in order to accurately describe the change process of bearing capacity of super-large ships after being damaged under extreme sea conditions,and to evaluate the final degree of collapse damage,the post-ultimate strength behavior of hull beams under ultimate wave loads is studied by using water elastic-plastic method.Considering the balance between the motion and hydrodynamic force of the hull beam structure,the unbalanced state caused by the large plastic deformation of the hull structure is compensated by the inertia force caused by the wave and the additional mass.The coupling equation between the structure and the load during the collapse of the hull beam structure is established,and the influence of different parameters on the collapse degree of the hull beam is analyzed.The nonlinear finite element method is used to calculate the post-ultimate strength behavior of the hull girder structure,and the design bending moment of the wave load is obtained by the wave load test of the pool,and then the scheme design of the hydroelastic-plastic mechanism test of the hull beam of the pool is completed.The main research contents are as follows(1)The coupling equation between the mathematical model of hull beam structure and the mathematical model of ultimate wave load is established,and the coupling equation is solved,and the solutions of each path equation of hull beam during collapse are obtained,and the influence of different parameters on the collapse degree of hull beam is analyzed.The collapse model of hull beam is simplified into a nonlinear spring system between two rigid body models to simulate the "plastic joint" formed by the collapse of hull beam structure.The nonlinear moment-curvature relationship of the spring system can precisely represent the constitutive relation of the hull beam structure.It includes elastic stage,buckling strength,ultimate strength,post-collapse ultimate strength behavior,and the whole curve variation law of the stiffness recovery stage when the structural system reaches the equilibrium state and is unloaded.(2)The finite element method is used to calculate the response process of hull beam structure under static load and dynamic load.The failure mode and ultimate bearing capacity of hull beam structure under two load modes are studied.(3)Aiming at the design of the keel beam model with a reduction scale ratio of more than 1:40 for the target ship,the wave load test of the tank is carried out to obtain the design moment of the model ship under the action of wave load.(4)According to the proportion relation between the design bending moment and the wave load test of the real ship,the section modulus of the collapse test model of the ship beam is determined,and the form of the test model is determined according to the stress response model of the real ship structure.After the design of the test model is completed,it is verified by finite element analysis and four-point bending test.Finally,the test component is assembled on the scale model of the hull beam to complete the design of the water-elastic-plastic mechanism test scheme.