Research On Collision Damage Mechanism Of Hull Structure Based On RTCL Failure Criterion

With the rapid development of the world economy,the economic ties between countries have become closer,and the unreasonable distribution of resources around the world has led to the rapid development of the shipping industry on a global scale.The increase in the number of ships has made the channel more congested in the limited space,coupled with the increase in speed,ship collision accidents often occur.at the same time.The increase in ship tonnage increases the impact of collision accidents,which often leads to disastrous consequences such as ship structural damage,casualties,and environmental pollution.Therefore,it is necessary to carry out the safety analysis of the hull structure in the relevant collision accident during the ship design stage.In addition,structural response analysis is carried out,and a typical hull structural response analysis prediction method is proposed,which provides a basis for the rapid design and optimization of crashworthy structures.There are three main methods commonly used to assess structural damage in accidents such as ship collision and grounding.They are test methods,finite element simulation methods,and simplified analytical methods.Under the premise of accurate parameter definition,the finite element simulation method can accurately predict the damage and deformation of the structure in the real scene,as well as the energy absorbed by each component,and is widely used by scholars at home and abroad.The simplified analytical method captures the deformation characteristics of the typical structure.The basic theory of plastic mechanics is used to obtain relevant response data,which is suitable for the preliminary design of anti-collision structures and the prediction of emergency handling methods.Therefore,this thesis takes the hull structure as the analysis object,and based on the force characteristics of the structure in the actual collision scene,the design is carried out.Tensile tests in various stress states were used to verify the revised RTCL failure criterion.On this basis,a cross-structure specimen with various stress states was designed according to the actual collision position,quasi-static stamping test and drop-weight collision test were carried out to verify the accuracy of the correction method,and finally the collision damage mechanism of typical hull members was studied.The specific content is as follows:(1)The main research methods and progress of ship collision and grounding problems at home and abroad are sorted out,and the characteristics of commonly used ductile metal failure criteria are compared and analyzed,and the main research content and ideas of the thesis are determined.(2)Through carrying out material performance tests,the problem of nonlinear simulation input of materials is discussed,which lays the foundation for the application of subsequent simulation methods;the basic principles,basic formulas and calculation steps of simplified analytical calculation methods are summarized,and the mechanism of damage and deformation of the cross structure is summarized.The research provides the basis.(3)Aiming at the shortcoming that the failure criterion is more sensitive to the grid size,a correction formula for the RTCL failure criterion is proposed,and the secondary development process of the VUMAT subroutine based on the plane stress element is briefly introduced,and the three stress states are designed and carried out.The tensile test compares and verifies the failure criteria before and after the correction.(4)Taking the cross structure of a typical ship hull as the research object,a quasi-static stamping test with a cross structure test piece and corresponding numerical simulation were designed and carried out,and the deformation characteristics of the ribs forming the cross structure were obtained,and the receiving surface of the cross structure was proposed.The deformation mode under internal load,through analyzing the energy dissipation mechanism of each deformation stage,obtains the analytical calculation formula for predicting the instantaneous resistance and average resistance of the cross structure under in-plane load.(5)The drop hammer impact test of the cross-structure specimen and the corresponding finite element simulation were carried out to verify the failure criterion of I-RTCL,and compared with the quasi-static test results,the influence of dynamic effects on structural deformation and damage was analyzed.