Elastic-Plastic Finite Element Analysis For Unequal-Diameter Tee Joint With Axial Through-wall Cracks At The Shoulder

Fracture mechanics has been used widely in practice with the development of the fracture mechanics theories and computer science. It is very important for service pipes to make safety assessments in application of fracture mechanics. However, fracture parameters are very scarce for some structures with crack in the safe estimation. Based on fracture mechanics, the unequal-diameter tee joint has been studied by adopting the finite element analysis method and using ANSYS. Including:(1) A finite tee joint model has been built and the stress of the tee joint has been analysis. The results indicate that there are stress focus at the part of the shoulder and belly of the tee joint when the tee joint subjected to internal pressure, internal pressure and bending. The two places are dangerous and incline to give birth to cracks.(2) The method which used to build the unequal-diameter tee joint with axial through-wall crack has been established. The finite element models of a center-cracked plane and a straight pipe with axial through-wall crack have been built and the stress intensity factors K₁ in different crack dimensions have been evaluated. The results of this study are in excellent agreement with the results provided by Kumar and EPRI, so the method can be used to build the tee joint model.(3) The tee joint entity model has been chosen by the study of the influence of diameter of the branch pipe and the length dimension of the run pipe and branch pipe. The finite element model has been built by the study of the influence of element distribution in crack district, axial direction, annular direction and the thickness of the pipe. The final model can satisfy the precision demanding and can also save time.(4) The stress intensity factors K₁ of the cracked tee joint have been evaluated when itsubjected to internal pressure, internal pressure and bending. Based on the stress intensity factor results, the shape factors have been calculated and the formulas have been given by curve fitting.(5) The full-plastic coefficient h₁ has been given under internal pressure and under different load ratio of internal pressure and bending. The stiffen-exponent n is introduced in the paper and the nonlinear material properties of ANSYS are defined with it. The center-cracked plane has been built to prove the transform. The J integral of the tee joint in...