Research on the Wrinkle Behavior of X80 Pipeline and B-Type Sleeve Repair Based on Finite Element Method

Pipelines are critical infrastructure for energy transportation, but long-term service under complex loading can cause local buckling failures. This study investigates the wrinkle behavior of API-X80 pipelines under combined internal pressure and bending using finite element analysis. The results show that increasing internal pressure significantly improves structural stability and delays wrinkle formation by suppressing cross-sectional ovalization. Wrinkle growth and protrusion height were quantified under various geometric and load conditions. Furthermore, a convex B-type sleeve repair method was modeled and optimized using response surface methodology and genetic algorithms. The optimized sleeve design effectively mitigates stress concentration around the defect area. This work provides a theoretical foundation for understanding wrinkle mechanisms and enhancing pipeline integrity under complex loads.