Local Buckling Behavior of 48^″, X80 High-Strain Line Pipes

Two bending tests of X80-grade, 48^″ high-strain line pipes pressurized to 60% SMYS were conducted to investigate local buckling behavior. The thickness and D/t ratio of the line pipes were 22.0 mm and 55.4, respectively. The mean Y/T ratio of the high-strain pipes was 0.82. A full-scale bending test apparatus was constructed to conduct the bending tests. The bending test results clarified that the pipes have the 2D average critical compressive strain of 1.51 and 1.67%, which satisfy the strain demand of 1.35%. Validation of FEA is conducted taking into account geometric properties of the pipes in terms of outside diameter and thickness and longitudinal flatness. The FEA results coincide with the test results with respect to peak load, critical displacement, critical rotation and critical compressive strain. The FEA results about the load and displacement relationship also show good agreement with the test results during post-buckling deformation. One developed wrinkle and some small wrinkles were observed on the pipe surface during post-buckling deformation, whose cross sections were fairly captured considering the geometric properties.