Research On Low Cycle Fatigue Strength Of Ship Stiffened Plate Based On Extended Finite Element Method

With the upsizing of ship and the widespread use of high strength steel,the fatigue problem of ship structure becomes more and more outstanding.Compared with the traditional method of S-N curve,fracture mechanics can explain the deep mechanism of fatigue crack growth,the extended finite element method(XFEM)based on fracture mechanics is a new way to research the fatigue strength of structures in recent years.Fracture mechanics and XFEM are introduced in this article.Based on XFEM,researchs on the fatigue strength of stiffened plates are conducted under the action of high stress and low frequency cyclic loading.The main content is as follows:(1)The stress intensity factors of the center penetrating crack of a infinite plate are calculated with the finite element method(FEM)and XFEM respectively,and the results are compared with the theoretical result.The validity of the numerical simulation method(XFEM)is verified.(2)Based on XFEM,The ultimate bearing capacity of slabs and stiffened panels with cracks under uniaxial tensile loading are calculated.The influencing factors of ultimate bearing capacity of cracked damaged members are analyzed.(3)The propagation rate of a crack under cyclic loading is calculated based on XFEM And compared with the result of the Paris formula curve,The fatigue strength of a flat plate subjected to cyclic loading is investigated with crack of Mode I and Complex crack of Mode ? and ?.(4)Based on XFEM,The fatigue strength of stiffened plates with crack damage under cyclic loading are calculated,the rule of structural fatigue degradation caused by fatigue crack propagation of reinforced concrete plates is summarized.