Stress Analysis Of Interlayer Defects In Thin-Walled Lining Recycled Composite Pipe

The aim of this paper is to study the stress distribution law of corrosion defects in pipelines before and after repair of thin-walled lining and the effect of repair. The calculation model for corrosion defects in pipelines was established by the equilibrium differential equation of elastic–plastic mechanics. Based on ABAQUS finite element software, the pipeline model with a single corrosion defect was established. The material of the pipeline was API 5L X52N with an outer diameter of 324mm and a thickness of 10mm. The material constitutive relation was an ideal elastic–plastic model. We changed the depth-to-thickness ratio of corrosion defects (d∕h=0, 0.1, 0.5, 0.8) and used the different lining repair materials (stainless steel and FRP). At the same time, ignoring the thickness of bonding layer and its influence on the filling of corrosion pit, the interface interaction analysis model was established by the bonding behavior between layers. We compared the stress at the corrosion defect before and after repair. It is found that with the increase of the depth-to-thickness ratio of corrosion defects, the radial stress, circumferential stress, and Mises stress at the corrosion defect all tend to increase. The circumferential stress at the defect before the repair is the largest, and its value is similar to the Mises stress. After the repair of stainless steel lining, the circumferential stress at the defect is reduced by 11.01%, and the Mises stress is reduced by 14.18%; after the repair of FRP lining, the circumferential stress at the defect is reduced by 7.01%, and the Mises stress is reduced by 3.54%. The depth-to-thickness ratio of corrosion defects has a significant impact on the stress distribution of pipelines. Therefore, the influence of corrosion depth should be paid attention to in the pipeline safety assessment. Before and after repair, the control stress at the corrosion defect of the pipeline is always the circumferential stress. The failure can be judged according to the circumferential stress; after the repair of thin-walled lining, the stress at the original defect is redistributed, and the circumferential stress and Mises stress are reduced, and the repair effect is obvious.