The purpose of this paper is to predict crack propagation and especially the remaining life after through-the-thickness crack at typical joints in deck and bottom structures of FPSOs. This information can be used in planning inspection, repair and maintenance. The growth of fatigue cracks is studied in typical welded joints through the use of analytical and numerical methods. The simplified analytical model is based on the British Standard 7910 [3] and Dexter’s analytical model [1–2]. Numerical analysis is performed with the finite element method, considering the effect of residual stresses, and using the J-integral approach to determine the stress intensity factor at the crack tip during different stages of crack growth. The first stage is referred the surface crack stage, in which the crack grows from an initial surface crack of a size of about 0.1 mm in depth and 0.2mm-1.0mm in length to the through-thickness crack. The second stage is named the long crack stage, in which the crack grows from an approximately 40–100mm long through-thickness crack to the final critical long crack. The computed stress intensity factors, along with the Paris law, are used to predict the crack propagation at each stage with reasonable accuracy. The effect of welding residual stresses on fatigue behaviour is considered by introducing an effective SIF concept. It is concluded that stable crack propagation behaviour can be conservatively predicted by using relatively simple approaches. These techniques can be used in making rational decisions regarding scheduling of inspections, repairs, and allow a better prediction of the structural reliability in view of fatigue cracks.
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ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering
June 12–17, 2005
Halkidiki, Greece
Conference Sponsors:
- Ocean, Offshore and Arctic Engineering Division
ISBN:
0-7918-4197-9
PROCEEDINGS PAPER
Analysis of Fatigue Crack Propagation in Typical Welded Joints of FPSOs Available to Purchase
Bin Zhang,
Bin Zhang
Norwegian University of Science and Technology, Trondheim, Norway
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Torgeir Moan
Torgeir Moan
Norwegian University of Science and Technology, Trondheim, Norway
Search for other works by this author on:
Bin Zhang
Norwegian University of Science and Technology, Trondheim, Norway
Torgeir Moan
Norwegian University of Science and Technology, Trondheim, Norway
Paper No:
OMAE2005-67058, pp. 35-42; 8 pages
Published Online:
November 11, 2008
Citation
Zhang, B, & Moan, T. "Analysis of Fatigue Crack Propagation in Typical Welded Joints of FPSOs." Proceedings of the ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. 24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 3. Halkidiki, Greece. June 12–17, 2005. pp. 35-42. ASME. https://doi.org/10.1115/OMAE2005-67058
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