Non-linear Finite Element Analysis For The Corrosion Defects Of Pressure Pipelines

Pressure pipeline is widely used in industrial production and people’s life. The safety of thepipeline is related to national welfare and the people’s livelihood. Along with the pipelineservice life growth, the corrosion defects will inevitably emerge. The existence of the corrosiondefects will affect the strength properties of the pipelines, and reduce the pressure-bearingcapacity significantly. Therefore, the residual strength of corrosion pipelines is necessary to beevaluated to ensure the safety of pipelines. Parameters that affect the failure pressure of apipeline with single corrosion defects were studied in the thesis. The interaction betweenadjacent corrosion defects and the influencing factors were also analyzed to provide thereferences for pressure pipeline safety evaluation.The burst pressure data of pressure pipelines were compared with the results of thenumerical calculation, and the accuracy of the finite element model of corrosion pipeline wasverified. The failure pressure predicted by non-linear finite element method using differentfailure criterion, such as elastic limit criterion, plastic limit criterion, plastic failure criterion,and numerical instability criterion were analyzed. It was found that the plastic failure criterionis most reliable for the burst pressure prediction with non-linear finite element method.Nonlinear finite element analysis for pipeline with single corrosion defect was carried out.The influence of geometrical shape and geometrical dimension of corrosion defect models onthe failure pressure prediction was studied， and the restrictive relation between eachgeometrical dimension parameter of defects was also analyzed. On the basis of previous studies,the3D model of long corrosion defect was simplified to2D model.The interaction effects of the axial adjacent corrosion defects and radial adjacent corrosiondefects were studied respectively by means of nonlinear finite element method. The maximumimpacting distance under different corrosion depth was obtained by numerical calculation. Thefinding of the analysis is that the corrosion depth and projective plane radius are two importantparameters for the maximum impacting distance, while depth ratio and length ratio of big tosmall corrosion defects have great influence on failure pressure of pipelines with radial adjacentcorrosions, but the width ratio has no impact on failure pressure. There is also a maximumimpacting distance between circumferential adjacent corrosion defects just as the central anglewhich represents the fraction of the circumference is20o. However, the corrosion depth has no impact on the maximum impacting distance of the circumferential adjacent corrosion defects.