Fatigue Testing and Analysis of Full Scale Girth Welded Tubulars

2007 ◽  
Author(s):  
Stig Wa¨stberg ◽  
Mamdouh M. Salama
Keyword(s):  
Fatigue Testing ◽  
Axial Loading ◽  
Full Scale ◽  
Fatigue Properties ◽  
Limiting Factor ◽  
Initiation Point ◽  
Fatigue Design ◽  
Axial Tension ◽  
Rotating Bending ◽  
Girth Welds

Heavy duty girth welded tubulars are used for many critical structural members offshore, e.g. free spanning pipelines, risers and tethers. The fatigue properties of those girth welds are often the design limiting factor. Today’s fatigue design rules for girth welded tubulars are mainly based on testing of segment specimens machined from a girth weld. Such specimens do strictly speaking not simulate all the features of a complete girth weld in a tubular. Lately some data have become available from rotating bending of full scale tubulars. However data from axial loading of full scale tubulars are rare. In this study full scale (OD 24”, 609.6 mm, thickness 0.812”, 20.6 mm) girth welded tubulars were fatigue tested in axial tension. Each tubular specimen contained three girth welds, equalling almost 6 m of weldment for each test. Both as-welded, TIG-dressed and ground weldments were included in the test program. The fracture surfaces were inspected for determination of the initiation point and its relation to welding flaws. The test results are compared to common fatigue design curves. The significance of embedded weld flaws in ground welds and the relationship to S-N curves for ground welds is discussed.

Full Scale Fatigue Testing of Fatigue Enhanced Girth Welds in Clad Pipe for SCRs Installed by Reeling

2008 ◽  
Author(s):  
Steinar Kristoffersen ◽  
Per J. Haagensen ◽  
Gisle Ro̸rvik
Keyword(s):  
Fatigue Test ◽  
Fatigue Testing ◽  
Fatigue Crack Initiation ◽  
Initiation Site ◽  
Full Scale ◽  
Fatigue Properties ◽  
Resonance Test ◽  
Pipeline Project ◽  
Girth Welds ◽  
Welding Procedure

H2S is reported to degrade the fatigue properties of C-Mn steels with a factor of 10–20 in life, while clad pipes are reported to have a performance close to or as good as in air. Clad pipes could therefore be used in highly fatigue loaded parts of the riser to facilitate design of steel catenary risers (SCRs) that are connected to floaters in deep waters. A literature survey of high quality girth welds intended for SCR is included in this paper and compared with fatigue test data obtained in this project. The first nine full scale 15" clad pipe girth welds out of a program of 24 specimens are fatigue tested in a high frequency resonance test rig and reported. The pipes were tested as welded, hammer-peened and reeled. The 15" OD steel pipes with 316 cladding tested in this work were surplus pipes from the Norne pipeline project. The fatigue test pipes were fabricated using the same welding procedure and welding facilities at Technip’s spool base in Orkanger, Norway, as the Norne pipeline project. The Norne pipeline is the world’s first reeled clad pipeline. The objective of this work was to test premium quality girth welds with best possible fatigue performance in actual pipes under realistic conditions was. The effect of hammer-peening of the OD was therefore investigated. Post failure examination was performed to determine the type and size of defects at the fatigue crack initiation site.

Fatigue Testing of Full Scale Girth Welded Pipes Under Variable Amplitude Loading

2012 ◽  
Author(s):  
Y.-H. Zhang ◽  
S. J. Maddox
Keyword(s):  
Fatigue Limit ◽  
Fatigue Damage ◽  
Fatigue Testing ◽  
Full Scale ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Fatigue Design ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Loading Spectrum

In the fatigue design of steel catenary risers there are concerns regarding the fatigue damage to girth welds from low stresses, below the constant amplitude fatigue limit, in the loading spectrum and the validity of Miner’s cumulative damage rule. In both cases there is increasing evidence that current design methods can be non-conservative. These fundamental issues were addressed in a recent JIP. A key feature was development of the resonance fatigue testing rigs to enable them to test full-scale pipes under variable amplitude loading. Such tests were performed under a loading spectrum representative of that experienced by some risers, with many tests lasting over 100 million cycles to investigate the fatigue damage due to small stresses as well as the validity of Miner’s rule. However, the resonance rigs are only capable of producing spectrum loading by gradually increasing or decreasing the applied load, whereas more ‘spiky’ random load sequences may be relevant in practice. Therefore the programme also included fatigue tests in conventional testing machines on strip specimens cut from pipes to compare the two types of loading sequence. This paper presents the results of these tests, conclusions drawn and recommendations for changes to current fatigue design guidance for girth welded pipes regarding the definition of the fatigue limit, allowance for the damaging effect of low stresses and the validity of Miner’s rule.

Tensile and Fatigue Properties of Friction Stir Processed NiAl Bronze

2007 ◽  
Vol 539-543 ◽  
pp. 3751-3756 ◽  
Author(s):  
Christian B. Fuller ◽  
Murray W. Mahoney ◽  
William H. Bingel ◽  
Michael Calabrese ◽  
B. London
Keyword(s):  
Fatigue Resistance ◽  
Fatigue Testing ◽  
Processing Parameters ◽  
Fatigue Properties ◽  
Friction Stir ◽  
Refined Microstructure ◽  
Property Data ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Property Characterization

Friction stir processing (FSP) produced local microstructural refinement in cast Ni Al Bronze. The refined microstructure quality was evaluated with mechanical property characterization using monotonic tension and fatigue testing as a function of FSP raster patterns. Modifying the cast NiAl bronze with FSP resulted in a 140 - 172 % increase in yield strength, and a 40 - 57% increase in tensile strength. Changing the raster pattern from a linear to a rectangular spiral raster increased the tensile elongations by 40 - 134%. This increase in elongation was attributed to increased microstructural uniformity through the depth of the FSP raster. The ability to transfer FSP technology was demonstrated with consistent tensile property data produced by three different laboratories. Fatigue characterization (both uniaxial and rotating-bending fatigue) showed that FSP improved the cast NiAl bronze fatigue resistance. Both types of fatigue testing showed differences in fatigue resistance as a function of processing parameters.

Fatigue Testing of Full Scale Girth Welded Pipes Under Variable Amplitude Loading

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Y.-H. Zhang ◽  
S. J. Maddox
Keyword(s):  
Fatigue Limit ◽  
Fatigue Damage ◽  
Fatigue Testing ◽  
Full Scale ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Fatigue Design ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Loading Spectrum

In the fatigue design of steel catenary risers, there are concerns regarding the fatigue damage to girth welds from low stresses, below the constant amplitude fatigue limit, in the loading spectrum and the validity of Miner's cumulative damage rule. These fundamental issues were addressed in a recent joint-industrial project (JIP). A key feature was development of the resonance fatigue testing rigs to enable them to test full-scale pipes under variable amplitude loading. Such tests were performed under a loading spectrum representative of that experienced by some risers, with many tests lasting over 100 million cycles to investigate the fatigue damage due to small stresses as well as the validity of Miner's rule. However, the resonance rigs are only capable of producing spectrum loading by gradually increasing or decreasing the applied load whereas more “spiky” random load sequences may be relevant in practice. Therefore, the program also included fatigue tests in conventional testing machines on strip specimens cut from pipes to compare the two types of loading sequence. This paper presents the results of these tests, conclusions drawn, and recommendations for changes to current fatigue design guidance for girth welded pipes regarding the definition of the fatigue limit, allowance for the damaging effect of low stresses, and the validity of Miner's rule.

A Comparative Mechanical Analysis of the Pointe Shoe Toe Box

1998 ◽  
Vol 26 (4) ◽  
pp. 555-561 ◽  
Author(s):  
Bryan W. Cunningham ◽  
Andrea F. DiStefano ◽  
Natasha A. Kirjanov ◽  
Stuart E. Levine ◽  
Lew C. Schon
Keyword(s):  
Structural Integrity ◽  
Fatigue Testing ◽  
Axial Loading ◽  
Mechanical Analysis ◽  
Static Strength ◽  
Fatigue Properties ◽  
Loading Conditions ◽  
Static Stiffness ◽  
Vertical Loading ◽  
Cycles To Failure

Dancing en pointe requires the ballerina to stand on her toes, which are protected only by the pointe shoe toe box. This protection diminishes when the toe box loses its structural integrity. The objectives of this study were 1) to quantify the comparative structural static and fatigue properties of the pointe shoe toe box, and 2) to evaluate the preferred shoe characteristics as determined by a survey of local dancers. Five different pointe shoes (Capezio, Freed, Gaynor Minden, Leo's, and Grishko) were evaluated to quantify the static stiffness, static strength, and fatigue properties (cycles to failure) of the shoes. Under axial loading conditions, the Leo's shoe demonstrated the highest stiffness level, and the Freed shoe exhibited the least strength. Under vertical loading conditions, the Leo's and Freed shoes demonstrated the highest stiffness levels, and the Gaynor Minden and Freed shoes exhibited the highest strength. Fatigue testing highlighted the greatest differences among the five shoes, with the Gaynor Minden demonstrating the highest fatigue life. Dancers rated the top five shoe characteristics, in order of importance, as fit, comfort, box/platform shape, vamp shape, and durability and indicated that the “best” shoe is one that “feels right” and permits artistic maneuvers, not necessarily the strongest or most durable shoe.

Results From Fatigue Testing of Subsea Wellhead Connector Segments

2021 ◽  
Author(s):  
Agnes Marie Horn ◽  
Pedro Barros ◽  
Anders Wormsen ◽  
Per Osen ◽  
Kenneth A. Macdonald
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Fatigue Testing ◽  
Fatigue Analysis ◽  
Full Scale ◽  
Test Method ◽  
Stress Fields ◽  
Test Results ◽  
Initiation Point ◽  
Drilling Rig

Abstract For subsea well drilling, the drilling rig is connected to the subsea well by a marine riser and subsea BOP equipped with a remotely controlled wellhead connector latched onto the subsea wellhead profile. The level of cyclic loading on subsea wellheads is steadily increasing due to use of increasingly larger drilling rigs with larger BOPs, the drilling of wells in harsher environments characterized by high waves. The remotely controlled wellhead connector forces a series of locking dogs into an externally machined profile on the wellhead. This external profile is generally referred to as a wellhead profile. The fatigue resistance of this safety-critical connector is typically estimated by finite element analyses (FEA). Due to the large size of the equipment, and high cost of testing, very limited fatigue testing, if any, has been carried out. A test method has therefore been developed, where a special test fixture is used to apply realistic boundary conditions and variable tensile loads to a small sector or segment of the wellhead connector. A primary objective is to generate fatigue-critical stress fields in the segments under tensile test load that closely replicates the stress fields in the full-scale wellhead connector. A secondary objective is to evaluate the possibility of using segment testing to determine the fatigue capacity of the full-scale connector. The testing of narrow sector segments allows the use of readily available test apparatus. It is thereby envisaged that the total cost of testing (specimens and test laboratory costs) can be substantially reduced in comparison with full-scale connector fatigue testing. This paper describes the fatigue testing of wellhead connector segments, and the test results in terms of cycles to failure and the failure modes, i.e. crack initiation point, and final crack geometry. The test scope consists of nine segments tested in-air at ambient temperature (nominal 20 °C), at a frequency of approximately 2 Hz under axial load of R = 0.1. At the time of writing this paper, six out of these nine tests have been performed. These six fatigue tests are presented in this paper. The test results are compared with estimates achieved by FEA of the test assembly and relevant S-N curves for the materials. It will be determined if the test results can be accurately predicted by the fatigue analysis methodology in Section 5.4 of DNVGL-RP-C203 (C203), including use of the new series of S-N curves for high strength materials in Appendix D.2 of C203. This design approach assumes that other failure modes (e.g. fretting or other local effects in the interface between components) do not govern the fatigue life, as this cannot be predicted by the fatigue analysis method applied here. The fatigue test set-up and the finite element analysis of the segment test is presented in the OMAE2020-18652 paper.

Comparison of Fatigue of Girth-Welds in Full-Scale Pipes and Small-Scale Strip Specimens

2008 ◽  
Author(s):  
Stephen J. Maddox ◽  
Yan-Hui Zhang
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Initiation ◽  
Fatigue Behaviour ◽  
Initiation Site ◽  
Full Scale ◽  
Fatigue Properties ◽  
Small Scale ◽  
Welded Steel ◽  
Steel Pipes ◽  
Girth Welds

As part of a study of fatigue in girth-welded steel pipes, tests were performed under constant amplitude loading on both full-scale pipes and strip specimens cut from such pipes. Significant differences were found in their high-cycle fatigue lives, which extended to around 108 cycles, and apparent fatigue endurance limits, the small-scale strips displaying superior fatigue properties. The reasons for this were investigated considering the fatigue crack initiation site, weld geometry, type of pipe, loading conditions, residual stresses, the re-testing of unfailed specimens and size effects. Fracture mechanics fatigue crack growth calculations were also performed using a K solution specially calculated by FEA for the girth weld. Conclusions are drawn about the suitability of strip fatigue test specimens for representing the fatigue behaviour of full-scale girth welded pipes and the scope for re-testing unfailed full-scale pipes.

Fatigue Performance of Thick Section Titanium Grade 29 Girth Welds

2020 ◽  
Author(s):  
Gabriel Rombado ◽  
David A. Baker ◽  
Lars M. Haldorsen ◽  
Kenneth Macdonald ◽  
Heath Walker ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Fatigue Testing ◽  
Fatigue Performance ◽  
Fluid Temperature ◽  
Design Curve ◽  
Fatigue Design ◽  
Dog Bone ◽  
Titanium Grade ◽  
Girth Welds ◽  
Welding Procedure

Abstract Design of Steel Catenary Risers (SCRs) requires the use of specialized connection hardware to mitigate the high dynamic bending moments at the hang-off location induced by host floater motion. Reliability of this connection hardware is imperative, especially in those applications involving high tension loads, high pressure and elevated fluid temperature. One option for connection hardware is a monolithic, metallic tapered stress joint. Because of its inherent density, strength, and stiffness properties, steel is not well suited for these applications due to excessive stress joint length and weight requirements. Titanium Grade 29 has been identified as an attractive material candidate for demanding service applications due to its unique mechanical properties including increased flexibility, excellent fatigue performance and corrosion resistance to sour fluids. This technology is well established in the offshore industry and utilized in over 60 SCR installations with operating lives exceeding 20 years of continuous subsea operation. Large titanium stress joints (TSJs) for deep-water applications are typically not fabricated as a single piece due to titanium ingot volume limitations thus making one or more intermediate girth weld(s) necessary to satisfy the overall length requirements. Fatigue testing of 38 mm (1.5-in) wall thickness girth welds, utilizing an optimized GTAW welding procedure to limit defect sizes to sub-millimeter, has previously been performed in seawater (OD exposure) under cathodic protection potentials and sour service (ID exposure) under galvanic potentials. Fatigue testing results fully verified the vendor S-N fatigue design curve, in addition, no appreciable differences in fatigue performance in environments were observed allowing project-specific testing to be limited to in-air testing. This paper presents in-air fatigue testing results of 51 mm (2.0-in) wall thickness Grade 29 girth welds, using the same optimized welding procedure, to assess thickness size effect on the vendor S-N fatigue design curve. Verification of the vendor fatigue design curve was demonstrated by testing curved dog-bone specimens, extracted longitudinally across the girth weld, with production level surface finishes on inner and outer surfaces in-air up to a predefined S-N fatigue target curve with 95% confidence level.

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