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.

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.

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

2011 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Stephen Maddox
Keyword(s):  
Fatigue Limit ◽  
Fatigue Damage ◽  
Fatigue Testing ◽  
Full Scale ◽  
Cumulative Damage ◽  
Constant Amplitude ◽  
Variable Amplitude ◽  
Testing Procedures ◽  
Fatigue Design ◽  
Damage Rule

In service the great majority of structures and components are subjected to stresses of variable amplitude (VA). The fatigue design of welded joints in such structures is based on fatigue data obtained under constant amplitude loading, used in conjunction with a cumulative damage rule to estimate the damage introduced by cycles of varying magnitude in the service stress history. There are two major concerns with fatigue design of deepwater steel catenary risers (SCRs): the validity of cumulative damage rule and the damaging effect of stresses below the constant amplitude fatigue limit (CAFL). It is known that SCRs can experience very high numbers of low stress cycles due to vortex induced vibration (VIV) with the result that the choice of method for accounting for the fatigue damage due to stresses below the constant amplitude fatigue limit can be highly significant in terms of the estimated fatigue life. These two fundamental issues have been addressed in a recent group sponsored project. By successfully establishing a loading spectrum representative of that experienced by risers and developing the testing procedures for VA loading using the resonance testing rigs, the fatigue performance of full-scale girth welded pipes under VA loading were investigated. These loading spectra had the same peak/maximum stress histograms but different minimum stresses. Many tests lasted over 108 cycles to investigate the fatigue damage of small stresses in these spectra. This paper describes the development of the method by which fatigue testing of full-scale girth welded pipes under VA loading had been successfully performed.

Improved Fatigue Design of SCR Modified Miner’s Rule

2019 ◽  
Author(s):  
Hans Olav Knagenhjelm ◽  
Mons Hauge ◽  
Bård Nyhus
Keyword(s):  
Carbon Steel ◽  
Stress Distribution ◽  
Fatigue Testing ◽  
Wave Spectrum ◽  
Fatigue Crack Initiation ◽  
Steel Pipe ◽  
Variable Amplitude ◽  
Fatigue Design ◽  
Miner’S Rule ◽  
Miner's Rule

Abstract The Aasta Hansteen floating production system is the first SPAR platform with steel catenary risers (SCR) at the Norwegian Continental Shelf (NCS). The water depth is 1300 msw. The weather conditions with respect to wave loading are more severe than any offshore installation completed so far. Under such environmental conditions, it is vital to verify the design of the SCR’s with respect to extreme loading and fatigue life. A fatigue verification program has been executed for ground OD welds of both clad and carbon steel riser materials. The objective was to determine the effect of weld defects in combination with the effect of variable amplitude loading using the actual fatigue stress distribution experienced by critical parts of the SCR. The stress distribution is based on the local wave spectrum and estimated from hydrodynamic analysis of the riser and the long-term wave statistics. Two clad pipes and one carbon steel pipe was exposed to rotation bending fatigue testing with artificially imposed defects. One clad pipes gave fracture after more than 1.0 × 109 cycles. The carbon steel pipe gave fracture after 4.56 × 108 cycles. A modified Miner’s summation rule is proposed for variable amplitude fatigue design. The procedure is based on a verification of variable amplitude testing against constant amplitude testing. The results indicate that load amplitudes below a fatigue limit defined at 107 cycles are not contributing significantly to fatigue crack initiation and growth from a weld defect. The proposed method suggests an engineering approach to this by a modification of the Miner’s rule for VA loading.

A Comparison of Fracture Mechanics and S–N Curve Approaches in Designing Drill Pipe

1992 ◽  
Vol 114 (3) ◽  
pp. 205-211 ◽  
Author(s):  
A. Ertas ◽  
G. Mustafa ◽  
O. Cuvalci
Keyword(s):  
Fracture Mechanics ◽  
Fatigue Damage ◽  
Drill Pipe ◽  
Ball Joint ◽  
Marine Riser ◽  
Deep Drilling ◽  
Miner’S Rule ◽  
Miner's Rule ◽  
Total Damage ◽  
Dynamic Fatigue

It is well known that the upper ball joint in a marine riser, in deep drilling, can cause fatigue damage in the drill pipe passing through it. A study of fracture mechanics and S–N curve approaches has been undertaken to determine the dynamic fatigue damage in the drill pipe. Miner’s rule is utilized in both methods to determine the total damage. The results of both methods are compared.

EXPLORATION OF CUMULATIVE DAMAGE EVOLUTION UNDER VARIABLE AMPLITUDE FATIGUE LOADING BASED ON WÖHLER CURVE

2021 ◽  
Author(s):  
RUI MIRANDA GUEDES
Keyword(s):  
Polymer Matrix Composites ◽  
Research Work ◽  
Fatigue Loading ◽  
Cumulative Damage ◽  
Damage Functions ◽  
Simple Assumption ◽  
Variable Amplitude ◽  
Stress Levels ◽  
Miner’S Rule ◽  
Miner's Rule

How to predict the residual strength of polymer matrix composites (PMCs) after a fatigue cycle at multiple stress levels, based on the fatigue or Wöhler (S-N) curves, remains unsatisfactorily tackled. The Miner’s Rule is a widespread example of a simple way to account for damage accumulation under different fatigue cycles. Under certain combinations of stress levels, Miner’s Rule accurately predicts the lifetime of PMCs, but it fails in other cases. The reason is the simple assumption of linear cumulative damage, not accounting for sequence effects in the loading history. Several researchers have proposed modifications to Miner’s Rule. However, due to its simplicity, Miner’s Rule is still used by structural designers. Recent research work proposed compatibility conditions for fatigue damage functions in the S–N plane, leading to a simple model that fulfils those conditions contrary to the previous models, the Miner’s Rule and the Broutman and Sahu linear model. These models predict fatigue life at variable amplitude loading based on constant amplitude fatigue data. Forcibly, the analytical form of SıN influences the model lifetime predictions. Experimental data obtained in the literature serves to illustrate the models' predictions at different loading conditions. Although this work focused on composite materials, we foresaw extension to other materials.

scholarly journals Fretting Fatigue under Variable Amplitude Loading below Fretting Fatigue Limit

2005 ◽  
Vol 71 (705) ◽  
pp. 763-768
Author(s):  
Yoshiyuki KONDO ◽  
Chu SAKAE ◽  
Masanobu KUBOTA ◽  
Hiroki KITAHARA ◽  
Kazutoshi YANAGIHARA
Keyword(s):  
Fatigue Limit ◽  
Fretting Fatigue ◽  
Variable Amplitude Loading ◽  
Variable Amplitude
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