Application Research Of The Extended Finite Element Method On The Cracks In Pressure Vessel

Pressure vessels are always used in petroleum industry,so it’s important to keep vessels safety.And the pressure vessel on the board is usually refers to the condenser on the ship,if there is a leak its consequences must be unbearable to contemplate.Now for the service pressure vessels,a tiny crack in welding position may lead to structural damages,so using the fracture mechanics method to research are very necessary.For the numerical simulation of the crack,considering the singularity problem in the traditional finite element method,the extended finite element method should be used to improve it.This paper based on extended finite element method with the guidance of fracture mechanics.Besides,containing defect pressure vessels will play as the research object,the work content is as follows:1.The research status of the pressure vessel and the extended finite element method at home and abroad,the methods of fracture mechanics problems in some application field of pressure vessels2.Carry on the elaboration to the fracture mechanics theory and method,introduce concepts,like the different types of crack stress intensity factor,the crack initiation,propagation of fatigue crack.And propagation mechanism of crack and residual life calculation method is also described.3.Through the basic theory of the extended finite element method,should analyses its differences from the traditional finite element method,like repeated grid’s division of crack tips,and the application of Abaqus platform to realize the numerical simulation of the extended finite element method.Calculating the three-dimensional crack down through the crack tips’ stress intensity factor in the numerical way,and according to the stress intensity factors of manual,searching relevant theoretical solution,to verify the theory,considering the calculation error and making appropriate analysis.4.The extended finite element method is applied to the pressure vessel structure,according to relevant design specifications and finite element method,it’s possible tocalculate the stress intensity factor on the edge of crack in different crack depths and lengths.In addition,through the calculation of traditional method to prove the calculation precision of the extended finite element method is reasonable,and finally combining the result with the MATLAB to calculate the critical crack size and the fracture mechanic parameters of residual life.5.Studying on coplanar cracks under the action of the three-dimensional distribution,ratio of stress field with single crack,the stress intensity factor of the crack fronts and crack tips.Further\more,discussing the relationship between the changes of stress intensity factor along with the influence of different factors.