Investigation On Fracture Failure Criterion Of Steel Material In Numerical Simulations For Ship Collision And Grounding Scenatios

With the rapid development of computing technology,numerical simulation technology has been used to study ship responses in collision and grounding scenarios.Numerical simulation can provide reliable and accurate simulation results,and has the advantages of saving time and cost.However,how to reasonably define the failure criterion of steel plate is still a challenge in finite element technology.Based on the BWH failure criterion,a set of formula for isotropic material considering hardening is proposed in this dissertation.LS-DYNA code is used to conduct secondary development.This proposed criterion is embedded in the LS-DYNA program.Then,using the upgraded LS-DYNA code,numerical simulations are carried out for an example of ship-grounding model test.By the comparison of numerical simulation results with those of the model test,the applicability of the proposed failure criterion is thus validated.The innovative research outcomes of this paper are summarized as below.1.The state-of-the-art of the development of material failure criteria in recent years and the application forms of different failure criteria is summarized for pointing out the advantages and disadvantages of different material failure criteria.In addition,the failure criteria in the numerical simulation of ship collision scenario and the basic features of the LS-DYNA program are briefly introduced.2.Based on the theoretical assumption of BWH failure criterion,a power law material model,J2 flow theory and Von Mises criterion are used to deduce a set of failure criterion formula for isotropic material considering hardening effect.3.The material failure criterion proposed is embedded into the LS-DYNA program by using the graph return algorithm in nonlinear finite element method and LS-DYNA secondary development theory.The failure criterion is embedded in the LS-DYNA program after programming,and the solver suitable for this failure criterion is compiled.4.Using a LS-DYNA secondary development program embedding the proposed failure criteria,a set of NSWCCD model stowage tests were simulated by finite element method.The results were compared with the experimental data to verify the rational applicability of the proposed material failure criterion.The research in this paper focuses on the improvement and application of steel material failure criteria in the finite element numerical simulation of ship collision and stranded scenario.The research content of this paper is of crucial significance for the accuracy and appropriateness of ship collision finite element simulation.