Assessment of Design S-N Curve for Umbilical Tubes

2009 ◽  
Author(s):  
Inge Lotsberg ◽  
Stein Fredheim
Keyword(s):  
Fatigue Test ◽  
Test Data ◽  
Design Methodology ◽  
Fatigue Analysis ◽  
Analysis Procedure ◽  
Fatigue Design ◽  
Reliable Design

A reliable design methodology for fatigue design of umbilical tubes is required by the industry. A documented design S-N curve is part of such a fatigue analysis procedure. During the last years a number of new fatigue test data have been derived for umbilical tubes. A design S-N curve for as welded and strained tubes during reeling has been debated. The present paper presents an overview of data presented in the literature. In addition it presents a significant number of fatigue test data of umbilical tubes performed at DNV test laboratories in Oslo. In addition it includes an assessment of recommended design S-N curve based on relevant available fatigue test data for umbilical tubes.

Assessment of the Size Effect in Fatigue Analysis of Butt Welds and Cruciform Joints

2014 ◽  
Author(s):  
Inge Lotsberg
Keyword(s):  
Size Effect ◽  
Fatigue Test ◽  
Test Data ◽  
Hot Spot ◽  
Plate Thickness ◽  
Fatigue Analysis ◽  
Analysis Model ◽  
Design Standards ◽  
Cruciform Joints ◽  
Fatigue Design

Reduced fatigue capacity of welded structures for larger thicknesses was introduced in design standards approximately 30 years ago. A significant amount of research on this topic was performed during the following years. In general the presence of a size effect was agreed upon. The size effect is considered to be dependent on the plate thickness at the considered hot spot in addition to size of attachment plate and type of dynamic loading. Only simplified recommendations on the size effect are included in most fatigue design standards. One reason for this is normal scatter in fatigue test data and also somewhat different recommendations based on these data in the literature. This has made it difficult to arrive at full agreement on recommended fatigue analysis procedures. In this paper a review of literature and design standards are presented together with a calibration of analysis method with fatigue test data. The effect of different parameters contributing to the size effect is illustrated. An attempt has been made to use the calibrated analysis model to also quantify the size effect based on crack growth analyses. Finally some recommendations on size effect to be used in fatigue design standards are presented.

Characteristic S-N Curves for Fatigue Design of Titanium Risers

2002 ◽  
Author(s):  
Knut O. Ronold ◽  
Stig Wa¨stberg
Keyword(s):  
Fatigue Test ◽  
Test Data ◽  
Base Material ◽  
Offshore Structures ◽  
Defect Size ◽  
Statistical Analyses ◽  
Stress Range ◽  
Fatigue Design ◽  
Range Interval ◽  
Lower Tolerance

A recommended practice for design of titanium risers is currently being developed as part of Det Norske Veritas’ series of standards and recommended practices for offshore structures. A recommendation is given herein for characteristic S-N curves for use in design of titanium risers against fatigue failure. As a basis for this recommendation, a set of statistical analyses of available fatigue test data have been carried out. Separate analyses have been carried out for base material and welds. The analysis results have been interpreted with respect to mean S-N curves as well as 97.7% lower tolerance bounds with 95% confidence. Characteristic S-N curves for base material and welds, which are not non-conservative with respect to these tolerance bounds, have been proposed. The paper presents the assumptions, the test data, the statistical analyses and their results, and the proposed characteristic S-N curves. The areas of application of the proposed curves are discussed with a particular view to stress range interval, material grade, weld position, temperature, and defect size.

Fatigue Capacity of FPSO Structures

2005 ◽  
Vol 128 (2) ◽  
pp. 156-161 ◽  
Author(s):  
Pål G. Bergan ◽  
Inge Lotsberg
Keyword(s):  
Finite Element ◽  
Numerical Methods ◽  
Fatigue Test ◽  
Test Data ◽  
Spectral Methods ◽  
Numerical Data ◽  
Design Basis ◽  
Calculated Stress ◽  
Structural Details ◽  
Reliable Design

This paper presents an overview of a joint industry project, addressing the problem of fatigue capacity of FPSOs (FPSO=ship shaped structures used for floating production storage and offshore loading). Spectral methods are becoming standard methodology for fatigue assessments of FPSOs. This methodology is well suited to numerical methods in combination with finite element representation of the global structure and structural details for response analyses. A proper link between calculated stress and fatigue capacity is required in order to achieve a reliable design. The project has generated significant amounts of numerical data as well as laboratory fatigue test data of typical ship details to improve the design basis for this. An overview of this project together with some links to the main results and recommendations from this project will be presented in this paper.

scholarly journals Experimental Data Assessment and Fatigue Design Recommendation for Stainless-Steel Welded Joints

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 723 ◽  
Author(s):  
Peng ◽  
Chen ◽  
Dong
Keyword(s):  
Stainless Steel ◽  
Fatigue Strength ◽  
Structural Steel ◽  
Fatigue Test ◽  
Test Data ◽  
Welded Joints ◽  
Steel Structures ◽  
Design Codes ◽  
Inverse Slope ◽  
Fatigue Design

Stainless steel possesses outstanding advantages such as good corrosion resistance and long service life. Stainless steel is one of the primary materials used for sustainable structures, and welding is one of the main connection modes of stainless-steel bridges and other structures. Therefore, fatigue damage at welded joints deserves attention. The existing fatigue design codes of stainless-steel structures mainly adopt the design philosophy of structural steel. In order to comprehensively review the published fatigue test data of welded joints in stainless steel, in this paper, the fatigue test data of representative welded joints of stainless steel were summarized comprehensively and the S–N curves of six representative stainless-steel welded joints were obtained by statistical evaluation. The comparison of the fatigue strength from existing design codes and fatigue test data was performed, and the results showed that the fatigue strength of welded joints of stainless steel was higher than that of structural-steel welded joints. The flexibility of regression analysis with and without a fixed negative inverse slope was discussed based on the scatter index. It was found that the fatigue test data of stainless-steel welded joints are more consistent with the S–N curve regressed by a free negative inverse slope. In this paper, a design proposal for the fatigue strength of representative welded joints of stainless steel is presented based on the S–N curve regressed by the free negative inverse slope.

Development of the Optimized Fatigue Analysis Procedure to Evaluate Design Life for APR1400

2008 ◽  
Author(s):  
Jaegon Lee ◽  
Taesoon Kim ◽  
Chankook Moon ◽  
Kwanghan Lee
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Life Time ◽  
Fatigue Analysis ◽  
Analysis Procedure ◽  
Design Curve ◽  
Fatigue Design ◽  
Design Life ◽  
Class 1

Fatigue is one of the most important failure mechanisms to assess integrity and design life of nuclear power plants. Fatigue analysis procedure and the standard fatigue design curve (S-N curve) for the class 1 components are given in ASME code section III NB. However, the existing ASME fatigue design curve does not address the effects of light water reactor coolant environment. The life time of ALWRs is designed for 60 years, and recently the plant life time of currently operating NPPs has been extended 20 years more. If we assess the integrity and design life of major components by fatigue analysis considering environmental factor and S-N curve, the estimated fatigue usage factor will not meet the criterion. In this study, detailed fatigue analysis using three dimensional models were performed to develop the optimized fatigue analysis procedure and their results were compared with other references. The locations considered are the pressurizer surge line, the CVCS charging inlet nozzle and the steam generator economizer nozzle of the advanced power reactor 1400 (APR1400).

Fatigue Capacity of Stiffener to Web Frame Connections

2009 ◽  
Author(s):  
Torbjo̸rn Lindemark ◽  
Inge Lotsberg ◽  
Joong-Kyoo Kang ◽  
Kwang-Seok Kim ◽  
Narve Oma
Keyword(s):  
Fatigue Test ◽  
Test Data ◽  
Large Scale ◽  
Fatigue Tests ◽  
Life Assessment ◽  
Shear Stresses ◽  
Test Model ◽  
The Difference ◽  
Marine Engineering ◽  
Plate Connections

Daewoo Shipbuilding & Marine Engineering Co., Ltd. (DSME), StatoilHydro and DNV established a common project to investigate the reason for the difference between calculated fatigue lives and the in-service experience and to assess the fatigue capacity of stiffener web connections subjected mainly to web frame shear stresses. The main objective of the work was to establish fatigue test data and perform numerical analysis of collar plate connections in order to provide improved confidence in analysis methodology for fatigue life assessment. Large scale fatigue tests of different types of connections were carried out to obtain fatigue test data of collar plate connections. Finite element analyses were carried out for comparison with fatigue test data and with measured stresses on the test model. Based on this work recommendations on fatigue design analysis of connections between stiffeners and web frames have been derived. The background for this is presented in this paper.

Fitting fatigue test data with a novel S-N curve using frequentist and Bayesian inference

2017 ◽  
Vol 105 ◽  
pp. 128-143 ◽  
Author(s):  
Davide Leonetti ◽  
Johan Maljaars ◽  
H.H. (Bert) Snijder
Keyword(s):  
Bayesian Inference ◽  
Fatigue Test ◽  
Test Data
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