High-grade (X100) Gas Pipeline Crack Arrest Technology Research And Finite Element Simulation

To reduce the pipeline engineering construction investment and save the use of steel, it tends to use high grade pipelines which have large diameter, high strength. During the running of batch production process and operation period, all kinds of fractures will be caused in the surface of the pipes. If these cracks are not be repaired in a timely manner, under the high pressure or ultra high pressure, they were likely to cause pipeline fracture failure to happen, seriously affecting the service life of the pipeline and pipeline operation safety. As the fiber composite materials are widely used in production practices, composite repairs for pipework have become the mainstream of high grade pipe rehabilitation technology.This thesis mainly researched on the repairing effect of glass fiber composite crack arrestor for surface cracks in high grade pipelines. By using the equivalent modulus of composite material, and comparing prediction models with the experimental value, the glass fiber laminate's mechanical properties were determined. Based on the ANSYS Workbench, a finite element simulation technology, we established the pipeline models with the surface cracks containing composite crack arrestors, and verified the reliability and stability of the J integral. By using the dimensionless parameters, the change laws among the influence factors, J integral and anti-crack coefficient (K value) were systematically analyzed, based on the models of the pipeline with axial semi elliptical surface crack and circumferential crack. To the pipeline with axial semi elliptical surface crack, the angle of composite layers had a significant impact, and the best angle was 60°. Increasing the thickness of composite crack arrestor appropriately could enhance the effect of crack arrestor. To the pipeline with circumferential semi elliptical surface crack, the best angle of composite layers was slightly less than that the axial crack had. As the length of crack arrestor and size of the crack increasing, the effect of crack arrestors was increased. But the effect of composite crack arrestors'thickness could be ignored.