scholarly journals Theoretical framework for estimating a product's reliability using a variable-amplitude loading spectrum and a stress-based approach

2018 ◽  
Vol 41 (8) ◽  
pp. 1662-1673 ◽  
Author(s):  
R.M. Portalés ◽  
M. del Mar Bochons Sania ◽  
J. Klemenc
Keyword(s):  
Theoretical Framework ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Loading Spectrum

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.

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.

In-Service Fatigue Performance of SCR Girth Welds Installed by Reeling

2012 ◽  
Author(s):  
Philippe P. Darcis ◽  
Eduardo Aguilar ◽  
Emma Erezuma ◽  
Israel Marines-Garcia ◽  
Eduardo A. Ruiz ◽  
...  
Keyword(s):  
Time History ◽  
Cumulative Damage ◽  
Fatigue Performance ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Failure Initiation ◽  
Service Conditions ◽  
Girth Welds ◽  
Damage Rule ◽  
Loading Spectrum

Interest arises on verifying the SCR girth welds fatigue response to a more representative loading spectrum of the actual in-service conditions and after reel-lay deformation. It is important to determine if the actual riser component’s qualification, without pre-straining and under constant amplitude loading, evidences discrepancies with in-service conditions, in terms of fatigue strength. This situation has motivated the full scale S-N fatigue performance evaluation of SCR girth welds under constant and variable amplitude loading, and after reel-lay simulations. A CMn steel X65 pipe 10.75” outside diameter (OD) and 25.4 mm wall thickness (WT) was chosen for this program. The Welding Procedure developed for girth welds manufacturing involved the use of the Lincoln STT® process for the root pass and the GMAW process for the fill and cap passes. Reeling trials were performed at Stress Engineering Services, Houston, U.S.A.. A dedicated commercial software was used to simulate the variable amplitude loading spectrum, which is representative of a SCR Touch Down Point (TDP) in West of Africa at a water depth of 1,200 m (3937 ft) and a FPSO as production platform. The experimental approach was focused on estimating the damage introduced by reeling and by loading cycles of various magnitudes in the riser service time history. Results of strained and unstrained specimens, tested at constant and variable amplitude, have been compared, and the cumulative damage rule typically used by Riser fatigue designers has been evaluated (i.e. Miner’s linear cumulative damage rule). Systematic fractographic investigations were performed on all the samples after testing to identify their fatigue failure initiation causes.

Hybrid Riser Resistance to In-Service Fatigue Loading

2014 ◽  
Author(s):  
Francesco Iob ◽  
Elisabetta Mecozzi ◽  
Luigi Di Vito ◽  
Philippe Darcis ◽  
Israel Marines-Garcia ◽  
...  
Keyword(s):  
Cross Flow ◽  
Complex Loading ◽  
Fatigue Loading ◽  
Fatigue Performance ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Riser Pipe ◽  
Wide Range ◽  
Girth Welds ◽  
Loading Spectrum

Riser systems are subjected to complex loading spectra. A wide range of amplitude loading are induced by naturally complex sea states. The complex loading spectrum differs sensibly from the constant amplitude loading commonly adopted for qualification of the product (riser pipe and its girth welds or threaded connections). The present paper reports numerical calculations and a comparison of the actual fatigue loading experienced by different riser systems, Steel Catenary Risers (SCR), Lazy Wave Riser (LWR), Hybrid Risers (HR). For the Hybrid riser system, a good fatigue resistance, due to the vessel and wave first motion decoupling, is obtained. On the other hand, the phenomenon of cross flow vibration induced by Vortex Induced Vibrations (VIV), could significantly affect the hybrid riser fatigue performance. In this case, a sensitivity analysis has been performed to evaluate the influence of different parameters, on the applied fatigue loading, like: riser tension, hydro diameter (i.e. external pipe diameter including coating), riser wall thickness, current velocity. The HR variable amplitude loading spectrum, derived from in-service conditions, referred to Gulf of Mexico scenario, has been calculated and applied in laboratory tests on girth welds of X65, 10.75″ OD, 25.4 mm WT riser. Furthermore, the fatigue performance of these tests has been compared to analogous tests on samples subjected to constant and variable amplitude loading available from previous work on SCR system[1].

Application of the Strip Yield Model to Crack Growth Predictions for Structural Steel

2010 ◽  
Vol 57 (1) ◽  
pp. 1-20
Author(s):  
Małgorzata Skorupa ◽  
Tomasz Machniewicz
Keyword(s):  
Structural Steel ◽  
Crack Growth ◽  
Model Calibration ◽  
Load History ◽  
Yield Model ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Constraint Factors ◽  
Strip Yield Model ◽  
Closure Mechanism

Application of the Strip Yield Model to Crack Growth Predictions for Structural SteelA strip yield model implementation by the present authors is applied to predict fatigue crack growth observed in structural steel specimens under various constant and variable amplitude loading conditions. Attention is paid to the model calibration using the constraint factors in view of the dependence of both the crack closure mechanism and the material stress-strain response on the load history. Prediction capabilities of the model are considered in the context of the incompatibility between the crack growth resistance for constant and variable amplitude loading.

Failure behavior of aerial bomb lifting lug under variable amplitude loading: Failure analysis and life prediction

2021 ◽  
Vol 120 ◽  
pp. 105000
Author(s):  
Bowen Wang ◽  
Liyang Xie ◽  
Jiaxin Song ◽  
Xuehong He ◽  
Weifeng Luo ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Life Prediction ◽  
Failure Behavior ◽  
Variable Amplitude Loading ◽  
Variable Amplitude
Sign in / Sign up

Export Citation Format

Share Document