Abstract The ultimate state of cracking in pipeline girth welds is influenced by multiple factors, including material, defects, and load. Full-scale pipe testing can truly reflect the loading conditions of pipeline girth welds and is the only test method that considers the effect of pipeline internal pressure on the fracture failure of girth welds. It is also the most accurate method for assessing the actual strain capacity of girth welds. This paper conducted four-point bending fracture tests on full-size pipes with crack-like defects and performed detailed mechanical response analysis through numerical inversion. The diameter of the test pipe is 1219 mm, the wall thickness is 22 mm, and the crack defect size is 15 mm × 300 mm. Additionally, tensile tests were performed on full-material round bars to determine detailed material property parameters. Strain gauges and Digital Image Correlation (DIC) systems were used to monitor key behaviors such as crack tip blunting in real time. By carefully recording the load-displacement response during the tests and combining synchronous monitoring results from external strain gauges and the DIC system, a deep comparative analysis was conducted to identify the critical failure states of the welded joints under both testing conditions. The finite element model of the full-scale pipeline was established by ABAQUS software, and the load-displacement curve of the pushing head position during the test was simulated. At the same time, the critical strain at the top of the whole pipe at the time of circumferential weld crack fracture is determined. Compared with the strain gauge results, the error is controlled within 15 %. The strain distribution of the girth weld position and the growth rate of CMOD during the test were obtained by DIC technology. The simulation results were not much different from the test results, which fully verified the high accuracy and reliability of the model. The data obtained from this full-scale test provide important evidence for validating the numerical model and its applicability assessment method for simulating pipeline girth weld fractures, and supplementing the international database for the strain capacity of 1219 mm large-diameter high-strength steel pipelines.
Liu et al. (Sun,) studied this question.