With the main aim of providing design guidance, fatigue endurance tests were performed on type S31803 duplex steel tubular T-joints. The test specimens were fabricated from two sizes of tube, 170 mm outside diameter (OD) × 7.5 mm wall thickness and 50 mm OD × 5 mm wall thickness. In line with normal industrial practice for duplex steel, the specimens were welded by the TIG process. The tests were carried out under in-plane bending at R = 0.1. In most joints, the brace was set onto the chord, but two specimens were made with the brace penetrating the chord to simulated pipework. The chord SCF was lower in the pipework joint than the tubular joint. However, all the results correlated on the basis of the hot spot stress range. The results were in reasonable agreement with those for similar joints in C-Mn steels, and hence the recently proposed CIDECT design curve.
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