| With the increasing scale of ships and the application of high-strength steel in ship construction,springing occurs frequently during navigation,which will significantly increase the fatigue load and damages on the fatigue strength of the hull structure.Computational fluid dynamics(CFD)can well describe the interaction between the hull and the fluid and the viscous effect of the fluid.It can simulate the real operating environment of the ship and accurately predict the wave induced vibration response of the ship.In this paper,CFD and nonlinear finite element method are combined to implement the two-way co-simulation,which is used to study the springing response of ships and the influence of springing on the fatigue damage of hull structures.During ship springing,the hull structure will encounter loads with two or more frequencies,and its stress response spectrum is bimodal spectrum or multimodal spectrum.At present,the bimodal spectrum fatigue damage calculation method is widely used to calculate the fatigue damage considering springing.But the bimodal spectrum method may cause error in the calculation of multimodal spectrum fatigue damage.Therefore,a fatigue damage calculation method considering multi peak characteristics of ship structure response is proposed in this paper to improve the calculation accuracy of fatigue damage considering springing.The main research contents of this paper are as follows:(1)The springing response of ship is studied by CFD-FEA co-simulation method.Firstly,the analysis procedures of studying ship springing response based on CFD-FEA co-simulation method is proposed.Then the dry and wet modes of the ship are calculated by finite element method.Finally,the motion response and wave load of the ship are calculated and compared with the test results to verify the accuracy of the simulation,and the effects of wavelength,speed and wave height on the springing of the ship are investigated.(2)The effect of wave induced vibration on fatigue damage of ship hull structure is studied.Firstly,a finite element refinement model is established for a typical node of the mid-ship section,and the hot spot stress concentration factor is calculated.Then the VBM time history obtained by numerical simulation is processed to determine the hot spot stress time history and stress power spectral density function,and the stress response characteristics of ship hull structure during springing are studied.Then the fatigue damage of typical structural details is calculated by different fatigue analysis methods,the influence of wave induced vibration on the fatigue damage of ship hull structure is analyzed,and the accuracy of fatigue damage calculation results considering wave induced vibration by different methods is compared.Then,the VBM time history obtained by numerical simulation is processed to obtain the hot spot stress time history and stress power spectral density function,the stress response characteristics of ship hull structure during springing are studied.Finally,the fatigue damage of the typical structural details is calculated by different fatigue analysis methods,the influence of springing on the fatigue damage of ship hull structure is analyzed,and the accuracy of fatigue damage results considering springing calculated by different methods is discussed.(3)The fatigue damage calculation method under the wave loadings of multi peak spectrum caused by springing is studied.Firstly,two traditional multimodal spectrum fatigue damage calculation methods,Dirlik method and Benasciutti and Tovo method,are introduced,and a fatigue damage calculation method considering multi peak characteristics is proposed.Then,the calculation results of the proposed method and two traditional multimodal spectrum methods are compared with the results of time domain method and bimodal spectrum method,the advantages and disadvantages of the traditional multimodal spectrum fatigue damage calculation methods are analyzed,and the reliability and accuracy of the proposed method are verified. |
PDF Full Text Request