This paper presents the results of fatigue and strength tests for: 1) cruciform joints with the fillet welds performed underwater, and 2) test coupons with one sided cut by Broco® underwater cut. The laboratory testing was conducted in air. The results show that the under-water fillet welds can have root cracking. For large root cracks this results in fatigue performance that is lower than the equivalent in-air welds without root cracks. In the absence of root cracks the DNV [3] approach for cruciform joints is shown to be applicable. The Broco® underwater cut edge cuts performed above the DNV category F3 [3] fatigue performance for the in-air environment, but below the Fl category. Hardness testing on the cut edge heat affected zoned surface showed values as high as 38 HRC. This is typically a concern for hydrogen stress cracking in offshore environments, and thus the using any category above the F3 curve likely is not justified. For in air testing the strength of the underwater welds and the Broco® underwater cut edges showed no appreciable strength reduction vs. what would be expected from conventional flame cut edges.
展开▼
