Research On The Structural Performance Of Ships Equipped With Airbag Protection

With the rapid development of China’s maritime economy,the number of ships at sea is increasing,and the density of ships in the channel is gradually increasing,which leads to the increasing incidence of ship collision accidents.Ship collision accidents are usually accompanied by structural damage,fuel leakage,environmental pollution and other problems,which will not only lead to economic losses,but also pose a serious threat to the marine ecological environment.The hull structure damage caused by collision is serious.The damage of water,cargo leakage,ship floating state change,etc.,will lead to the longitudinal strength and local strength of the ship being greatly weakened,which will have a great impact on the rescue and towing process.Therefore,in the stage of ship design,it is of great practical significance to evaluate the crashworthiness of the structure,install the anti-collision structure in the weak area,apply the flexible anti-collision device to the field of ship anti-collision,carry out the research on the characteristics of ship collision damage before and after the installation of airbag protection,and evaluate the residual strength of the damaged hull after collision damage,so as to effectively reduce the degree of accident harm and avoid such catastrophic consequences.Based on a project,this thesis firstly takes the response characteristics of the falling ball collision plate frame structure as the research object,establishes the collision numerical simulation technology based on the dynamic display method,and verifies the reliability of the collision numerical simulation technology by comparing the stress damage and the collision force-collision depth curve in the test.Based on the validated numerical technique,a numerical simulation model of ship collision under typical collision scenarios is established.The effects of different collision angles and collision speeds on the damage of hull structure are analyzed from the perspective of internal and external mechanisms.Then,from the point of view of protecting the weak parts and enhancing the crashworthiness of the structure,aiming at the simplified structure of the midship side,the numerical simulation technology of the crashworthiness simulation of the simplified structure of the midship side with airbag protection is established by using the fluid cavity model,and the crashworthiness of the simplified structure of the midship side with airbag protection is studied.Through the parametric influence analysis of airbag overload response with different thickness and different elastic modulus,the airbag parameters with better buffering characteristics are found.Then,the numerical simulation technology of ship collision structure response under airbag protection based on dynamic display method is established by nonlinear finite element software Abaqus.The damage of hull structure before and after airbag protection under different collision angles and different collision speeds is compared and studied.Finally,the progressive failure process analysis is carried out for the hull girders of the intact structure,the unprotected collision damage and the ship collision damage under the protection of the airbag.The residual strength of the hull girder before and after the airbag protection is carried out based on the quasi-static method.The protection effect of the airbag structure on the ship collision is measured,and a method for evaluating the residual strength of the ship collision based on the quasi-static method is proposed to measure the protection effect of the airbag on the hull structure.The main contents of this thesis are as follows:(1)The basic theories of explicit solution method,material model and its constitutive,airbag finite element method,contact algorithm and fluid-solid coupling method are introduced,which provide theoretical support for the subsequent numerical simulation technology.(2)Based on the guidance of the above theory,taking the response characteristics of the falling ball collision plate frame structure as the research object,the collision numerical simulation technology based on the dynamic display method is established by using the large-scale nonlinear finite element software Abaqus,and the collision numerical simulation technology is verified by comparing the stress damage and the collision force-depth curve in the test.Combined with the typical scene of ship collision obtained from literature research,the hull structure is established by using the large-scale finite element software Patran.Based on the verified numerical technology,the numerical simulation model of ship collision based on dynamic display method is established by using the large-scale nonlinear finite element software Abaqus.The influence of different collision angles and impact velocities on the damage of hull structure is analyzed from the perspective of internal and external mechanism,which provides a reference for the study of ship collision structure response with airbag protection.(3)Based on the influence of different collision angles and impact velocities on the damage of hull structure,from the perspective of protecting weak parts and enhancing structural crashworthiness,a numerical simulation technology for the crashworthiness of simplified midship side structure with airbag protection is established by using fluid cavity model.The crashworthiness of simplified midship side structure with airbag protection is studied from the aspects of stress and damage,collision force and energy conversion.Through the parametric influence analysis of airbag overload response with different thickness and elastic modulus,the airbag parameters with better buffering characteristics are found.(4)The numerical simulation technology of ship collision structure response under airbag protection based on dynamic display method is established by nonlinear finite element software Abaqus.From the aspects of stress cloud diagram,damage deformation,collision force and energy conversion,the hull structure damage before and after airbag protection under different collision angles and different impact velocities is compared and studied.The nonlinear finite element method is used to calculate the residual ultimate strength of the hull girder.Firstly,the influence of loading rate on the calculation results of ultimate strength is analyzed by selecting the solution method,adjusting the element type and mesh size.Secondly,the ultimate strength of hull girder before and after the installation of airbag protection based on quasi-static method is studied.Finally,combined with the stress and deformation diagram obtained by finite element calculation,the process of gradual destruction of hull girder after collision damage without protection and ship collision damage with airbag protection is compared and analyzed when the hull girder is in complete structure respectively.The protective effect of airbag structure on ship collision is measured,and a method of evaluating the residual strength of ship collision based on quasi-static method is proposed to measure the protective effect of airbag on hull structure.