Residual Strength Evaluation Of Elbow With Defect

The pipeline system is usually provided with elbows to change the direction of the pipeline.Due to the special geometric characteristics of elbow,the stress is different from that of the straight pipe.When other external loads are applied,stress concentration is more likely to occur at the elbow,and then failure occurs.Many of the oil and gas pipeline accidents are caused by the failure of the elbow.Therefore,it is very meaningful to study the effect of corrosion defect at the elbow on the failure of the pipeline.In this paper,the elbow in the pipeline system is taken as the research object,and the finite element model of the elbow without defects,with pitting defects and with local thinning defects is established respectively.After mesh division,boundary condition determination,load application and nonlinear calculation,the analysis of the yield failure of the elbow under the action of internal pressure and buckling failure under the action of the bending moment is carried out.The influencing factors of the limit load are analyzed to obtain the corresponding plastic limit load.In-depth research and discussion of the failure status of the elbow,summarized the various influencing factors,including the diameter,wall thickness,bending diameter,defect size and position,etc.,on the limit load.Finally,formulas and conclusions with certain guiding significance for pipeline inspection,repair and maintenance in actual engineering are obtained.