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State-of-the-art: Fatigue life extension of offshore installations
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.ORCID iD: 0000-0003-4180-4710
2012 (English)In: Proceedings of the ASME 31st International Conference on Ocean, Offshore and Arctic Engineering--2012: presented at ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering, July 1-6, 2012, Rio de Janeiro, Brazil, ASME Press, 2012, 9-20 p.Conference paper (Refereed)
Abstract [en]

The use of fatigue life improvement techniques and specifically ultrasonic peening treatment to extend the service life of offshore structures has become an accepted practice during the last five years. The understanding of the process as well as equipment's upgrading for treatment in-situ including quality control and assurance have been developed up to a level that it has become a current practice in many parts of the world. However, the efficiency of the ultrasonic peening is strictly dependent on the deep understanding of significant fatigue parameters as weld defects, stress concentrations and residual stresses and their interaction. In this paper we attempt to present the current knowledge and the physical reasons why the ultrasonic peening treatment is able to improve the fatigue life of welded joints. The local weld geometry or stress concentration, weld imperfections as well as welding residual stresses are all modified and improved by the application of ultrasonic peening. Local weld geometry and weld process inherent weld imperfections are the factors primarily influencing the fatigue strength in welded joints. Comprehensive studies have been carried out during the last 20 years in order to detect and document the weld defects as well as to understand their origin and effect on the fatigue strength of welds. Analogous efforts have been dedicated to understand and document the influence of local weld geometries on the stress concentrations and its influence on endurance and structural integrity. Similarly, efforts have been done to understand the influence of the relaxation by external loads of the by the ultrasonic peening treatment induced compressive stresses. Fatigue test results of ultrasonic peening treated relevant weld details have been used to assess the potential life extension. The results showed four to six times fatigue life extension. The spectrum fatigue test was designed to confirm that relaxation by service loads of the induced compressive stresses during ultrasonic peening treatment would not diminish the benefit.

Place, publisher, year, edition, pages
ASME Press, 2012. 9-20 p.
Keyword [en]
Current practices, Fatigue life improvement, Fatigue parameter, Offshore installations, Spectrum fatigue, Ultrasonic peening, Ultrasonic peening treatment, Welding residual stress
National Category
Other Materials Engineering
URN: urn:nbn:se:kth:diva-144784DOI: 10.1115/OMAE2012-83044ISI: 000324655500002ScopusID: 2-s2.0-84884475262ISBN: 978-079184493-9OAI: diva2:716694
ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2012; Rio de Janeiro; Brazil; 1 July 2012 through 6 July 2012

QC 20140512

Available from: 2014-05-12 Created: 2014-04-29 Last updated: 2014-05-12Bibliographically approved

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Barsoum, Zuheir
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