Numerical Simulation Study On Fracture Fatigue Properties Of Submersible Cone And Column Structure

As an important part of the cylindrical pressure-resistant shell of large submersibles,the cone-column structure is prone to fatigue damage due to its special structure form.The study of submersible pressure shell fatigue is research focus.With the expansion of the submersible operating range and the improvement of safety requirements,it is difficult for ordinary high-strength steel to meet the requirements for the safety and layout of the submersible pressure-resistant shell.Titanium alloy can effectively solve the problems of submersible weight and corrosion control due to its high specific strength and good corrosion resistance.It is the research direction of future submersible pressure shell materials.Therefore,linear elastic fracture mechanics is of great engineering significance to study the fracture fatigue characteristics of cone-column structure,which is bulit by titanium alloy material.Based on linear elastic fracture mechanics,the surface crack propagation and fatigue life of TA31 conical column were studied by numerical analysis methods.The Ansys-Franc3 D software was used to analyze the distribution of ?,?,?-type stress intensity factors of surface cracks in the cone-column structure,and the rationality of the fracture fatigue characteristics of the structure was considered.The influence of the crack shape ratio on the distribution of the I-type stress intensity factor value at the leading edge of the surface crack was studied,and the critical crack size of the structure under different shape ratios was calculated.The quasi-static method for numerical simulation of crack propagation is studied.The proposed parameters of crack propagation shape change and structural life calculation using dN and da quasi-static method are given.Based on the composite crack brittle fracture criterion,the rationality of the I-shaped crack plane expansion mode of the cone-column structure is verified.Finally,based on the expansion mode,the two-degree-of-freedom crack leading edge curve fitting method is applied,and the initial crack size is 5mm.Numerical simulation of crack propagation and fatigue life calculation of surface cracks in cone-column structures is completed.In this paper,the liner elastic fracture mechanics theory and Ansys-Franc3 D simulation method are used to study the parameters related to fatigue numerical simulation,and the critical crack size calculation and fatigue life prediction of cone-column structure are completed.The research results have certain reference significance for the study of fracture fatigue characteristics of similar structures..