Fatigue Life Improvement of Welded Doubling Plates

2012 ◽  
Author(s):  
Inge Lotsberg ◽  
Arne Fjeldstad ◽  
Morten Ro Helsem ◽  
Narve Oma
Keyword(s):  
Fatigue Life ◽  
Fatigue Testing ◽  
Fatigue Cracking ◽  
Offshore Structures ◽  
Life Assessment ◽  
Fatigue Life Assessment ◽  
Life Improvement ◽  
Structural Connections ◽  
Weld Root ◽  
Assessment Procedures

Fatigue life assessment is important for all floating offshore structures related to the new building stage but also related to lifetime extensions. Fatigue cracking occurs normally due to uncertainties in estimated fatigue life and this is a well-known problem for floaters. In this paper the aim has been to look deeper into the effects of improvement methods for improvement of the fatigue life of structural connections. Fatigue testing of full size fillet welded doubling plates has been performed of a specimen in as welded condition for comparison with two specimens improved by grinding. The paper also presents an alternative S-N curve for grinded details. The primary goal is to assess the possibility for fatigue life improvement of fillet welded doubling plates where fatigue cracking may initiate from the weld root. The information gained in this project is considered to be important for the offshore floater industry, as well as for development of new fatigue assessment procedures and requirements in standardization.

Research on the Fatigue Character of ERW Pipe Welded Seam and Fatigue Life Assessment Method

2010 ◽  
Author(s):  
Guangli Zhang ◽  
Jinheng Luo ◽  
Xinwei Zhao ◽  
Hua Zhang ◽  
Liang Zhang ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Stress Ratio ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Assessment Method ◽  
Life Assessment ◽  
Repeated Loading ◽  
Fatigue Crack Propagation Rate ◽  
Line Pipe ◽  
Fatigue Life Assessment

The fatigue character of electric resistance weld (ERW) seams in API X65 grade line pipe steel at the stress ratio of 0.1 and 0.6 have been investigated. Repeated loading was applied to compact tension specimen, and the fatigue crack propagation rate and threshold of X65 ERW pipe seam are tested using high-frequency fatigue testing machine. Radiographic inspection has shown that the crack caused by the cold welding is the main weld defect in the ERW pipe. Based on the failure assessment diagram (FAD) recommended in the API 579-2007 and the Miner’s linear cumulative damage model, considering the influence of stress ratio to the fatigue life, the fatigue life assessment method for the ERW pipe containing seam defects is established.

scholarly journals Mapping of scatter in fatigue life assessment of welded structures—a round-robin study

2021 ◽  
Author(s):  
Gustav Hultgren ◽  
Mansoor Khurshid ◽  
Peter Haglund ◽  
Zuheir Barsoum
Keyword(s):  
Fatigue Life ◽  
Round Robin ◽  
Life Assessment ◽  
Fatigue Life Assessment ◽  
Fatigue Life Estimation ◽  
Box Structures ◽  
Load Carrying ◽  
Local Stresses ◽  
Sources Of Variation ◽  
Global And Local

AbstractA round-robin study has been carried out within a national project in Sweden with the addition of an international participant, where several industrial partners and universities are participating. The project aims to identify variation and sources of variation in welding production, map scatter in fatigue life estimation, and define and develop concepts to reduce these, in all steps of product development. The participating organisations were asked to carry out fatigue life assessment of welded box structures, which is a component in load-carrying structures. The estimations of fatigue life have also been compared with fatigue test results. Detailed drawings, loads and material data were also given to the participants. The participants were supposed to use assessment methods based on global and local stresses using the design codes or recommendations they currently use in-house. Differences were identified between both methods and participants using the same codes/recommendations. Applicability and conditions from the cases in the codes were also identified to be differently evaluated between the participants. It could be concluded that for the applied cases the nominal stress method often overestimated the fatigue life and had a high scatter in the estimations by different participants. The effective notch method is conservative in comparison to the life of tested components with little scatter between the results derived by the participants.

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