Buckling and Tensile Strain Capacity of Girth Welded 48″ X80 Pipeline

Abstract

This paper presents the experimental and analytical results focused on the compressive and tensile strain capacity of X80 linepipe. A full-scale bending test of girth welded 48″ OD X80 linepipes was conducted to investigate the compressive strain limit regarding to the local buckling and tensile strain limit regarding to the girth weld fracture. As for the compressive buckling behavior, one large developing wrinkle and some small wrinkles on the pipe surface were captured relatively well from observation and strain distribution measurement after pipe reaches its endurable maximum bending moment. The tensile strain limit is discussed from the viewpoint of competition of two fracture phenomena: ductile crack initiation / propagation from an artificial notch at the HAZ of the girth weld, and strain concentration and necking / rupture in the base material. The ductile crack growth behavior from the girth weld notch is simulated by FE-analysis based on the proposed damage model, and compared with the experimental results. In this report, it is also demonstrated that the simulation model can be applicable to predicting ductile crack growth behaviors from a circumferentially notched girth welded pipe with internal high pressure subjected to post-buckling loading.