Research On Dynamic Response And Deformation Mechanism Of Ship Structures Under Ship Oblique Collision Scenario

Ship collision accidents will lead to ship structural damage,and cause casualites,economic losses and environmental pollution with serious public concern.In order to improve the safety of hull structure and avoid serious losses in ship collision accidents,it is of great significance to evaluate the crashworthiness of hull structure in a quick and accurate way during the ship design stage.At present,the researches on ship collision mainly focus on the scenarios of head-on ship collision.However,according to the statistical data,the probability of oblique ship collision accidents is higher than that of head-on ship collision accidents.Therefore,the current researches on oblique ship collision scenario is insufficient.The responses of ship side structure in the oblique ship collision scenarios are different from those in head-on ship collision scenarios.Oblique collision will cause a wider range of structural damage and even more serious consequences.The deformation of hull structure in oblique collision scenarios also shows high nonlinear characteristics.In addition,applicaton of an accurate material model in the numerical simulation and obtaining of the deformation characteristics of hull structure in the analytical method are still challenges in marine industry.In this paper,the deformation mechanism of ship side structure in oblique ship collision scenarios is studied by using the analytical method and finite element numerical simulation method,and the main research outcomes are as follows:(1)Based on micromechanics,a material model based on the Johnson-Cook model and the Gurson-Tvergaard-Needleman(GTN)model is proposed,hereinafter referred to as the Johnson-Cook GTN model.The proposed material model not only considers the material stress-strain property and the strain rate effect,but also combines the growth and coalescence of holes,which can describe the ductile fracture process of steel more accurately.In this study,the proposed Johnson-Cook GTN model is embedded into the finite element software LS-DYNA,and the response of hull structure can be better predicted in the finite element numerical simulation of ship collision scenarios.(2)In order to verify the accuracy of the proposed Johnson-Cook GTN model,experiments are conducted.The quasi-static tensile test is carried out to obtain the mechanical property parameters of the material,and high-speed tensile test is carried out to obtain the stress-strain relationship curves of the material at different strain rates.Then,the stress-strain relation curves of material at different strain rates are converted into "composite material relation curves",which can be used as the input of material parameters in numerical simulation.The results of numerical simulations using the proposed Johnson-Cook GTN model match well with the testing results of quasi-static tensile test,falling weight impact test and ASIS test a.It is proved the accuracy and applicability of the proposed Johnson-Cook GTN model,and indicates that the proposed material model can be used to predict the structural damage in ship collision scenarios.(3)For the scenario of a raked bow oblique collision with ship side structure,the deformation mechanism of the main components of ship side structure is analyzed.The theoretical deformation models of the side plating,the web girder and the transverse frame are proposed,and the analytical calculation formulas of these three components under different oblique collision angles are derived.The dynamic response of the side structure can be predicted by integrating the deformation resistance formulas of the side plating,the web girder and the transverse frame.According to the differences of the collision positions and collision angles of the raked bow,six typical oblique collision scenarios are defined,the proposed Johnson-Cook GTN material model is used for numerical simulations in the finite element software LS-DYNA,the numerical simulation results are used to verify the analytical calculation results.(4)For the scenario of a bulbous bow oblique collision with ship side structure,an analytical calculation method is proposed to predict the dynamic response of side structure.The analysis method is applied to analyze the deformation mechanism of the main components of the ship side structure,the theoretical deformation models of the side plating,the web girder and the transverse frame are proposed,and the analytical calculation formulas of the three components under different oblique collision angles are derived.Superimposing the deformation resistance of the three structural components to predict the crashworthiness of the ship side structure.According to the different collision positions and collision angles of the bulbous bow,six typical oblique collision scenarios are defined,the proposed Johnson-Cook GTN material model and the finite element software LS-DYNA are used for numerical simulation to verify the accuracy of the analytical calculation results.The proposed Johnson-Cook GTN model in this paper can be used in the numerical simulation analysis of ship collision problems,for the research results of raked bow and bulbous bow collision with ship side structure.It is of good engineering application value in the crashworthiness design and crashworthiness evaluation of ship side structure.