Full Scale Fatigue Experiment on Submarine Pipelines

This paper focus on fatigue problem of submarine pipelines, four points bending full scale fatigue experiment were conducted on X65 pipelines butt joints specimens, utilizing pipeline full scale fatigue test machine developed by CNPC. Meanwhile contrast test was also carried out on small specimens. The results show that the fatigue strength of full scale welded joints is lower than the small scale joints. Owing to having no regard for the influence of residual stress and size effect, the small test would provide dangerous results. The fatigue property of full scale welded joints only meets the requirement of DNV C203 W3 curve, and meets the needs of DNV C203 F3 curve basically while not meet BS 7608 F2 curve’s requirements which relatively demand higher. Weld toe and geometric discontinuous near weld root is the weak point for the whole welded joints.