FATIGUE OF 28-INCH TITANIUM RISER - SN DATA AND DEFECT ASSESSMENT

摘要

Qualification testing was carried out on full scale titanium pipes for a gas export riser from the Asgard B platform. Prototype pipe sections with girth welds produced by the TIG process were delivered from three different suppliers. The wall thickness was 30 mm. The pipes were sectioned into fatigue specimens and tested in constant amplitude loading in air. The loading was transverse to the weld, simulating axial and bending loading of the pipe. Secondary stresses were measured on each specimen. SN data were obtained for the welds and compared with proposed design curves. The fracture surfaces were investigated with scanning electron microscopy, and defects were categorised and sized. Fracture mechanics analysis was carried out and the results were compared with experimental data. Problems relating to fracture mechanics modelling for fatigue life prediction and defect assessment of titanium welds were discussed.