Fatigue Crack Growth Rates in Six Pipeline Steels

Bussiba, A.; Darcis, Philippe; McColskey, Joseph D.; McCowan, Christopher N.; Kohn, G.; Smith, Robert W.; Merritt, James

doi:10.1115/ipc2006-10320

Cited by 4 publications

(6 citation statements)

References 5 publications

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“…Table 2 lists the final flaw geometries and their associated initial notch sizes that were prepared by EDM, and the corresponding constant to relate the stress-intensity factor, K (MPa√m ) to the outer fiber bending stress (MPa). Based upon FCGR data from the literature [6][7][8][9][10] a stress-intensity factor of between 15.4 MPa√m and 33.0 MPa√m would be required to generate a sufficient fatigue crack growth rate (FCGR). This stress-intensity factor range would provide fatigue crack growth rates between 0.025 µm and 0.25 µm per cycle [9][10] .…”

Section: Stress-intensity Factor Analysismentioning

confidence: 99%

Fatigue Pre-Cracking Curved Wide Plates in Bending

Richards

Weeks

McColskey

et al. 2010

2010 8th International Pipeline Conference, Volume 4

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Curved wide plate (CWP) testing in tension, on API 5L X100 pipes of 36-inch (916-mm) diameter and 0.75-inch (19-mm) wall thickness, has been initiated in support of strain-based design using high strength steel for oil and gas pipeline applications. The CWP tests are being used to optimize and validate welding procedures and to determine the defect tolerance within the girth welds. A traditional pre-requisite for fracture mechanics testing is a final extension of a crack via fatigue pre-cracking to produce a representative flaw. A method of fatigue pre-cracking CWP specimens for final notch preparation in bending was developed to meet ASTM guidelines for fracture mechanics testing. Fatigue pre-cracking for the present specimen geometry was possible in bending due to lower requisite force capacity equipment which allowed for greater cyclic loading frequencies. In order to achieve sufficient stress levels for fatigue crack growth in the curved plate, a stress field analysis was performed to optimize the loading support configuration in four-point bending. In addition to the stress field analysis, a 3-D finite element model of the CWP specimen was generated to analyze the notched CWP specimen in four-point bending. Finite element analysis (FEA) results and experimental data were used to confirm the hypothesis that, under the proposed loading arrangement, the closed-form solutions for stress-intensity (K) of flat plates in bending can be used to approximate the K for CWP specimens in bending. Validation of a solution for stress-intensity factor subsequently allowed the determination of force amplitude levels for fatigue crack growth. Force and crack mouth opening displacement (CMOD) data were analyzed to correlate compliance with crack length measurements. From experimental results, a method was developed that enable the repeatable and well characterized extension of surface flaws by fatigue pre-cracking in curved wide plate specimens in bending.

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Section: Stress-intensity Factor Analysismentioning

confidence: 99%

Fatigue Pre-Cracking Curved Wide Plates in Bending

Richards

Weeks

McColskey

et al. 2010

2010 8th International Pipeline Conference, Volume 4

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“…In addition a flat M(T) specimen was also modeled. A plot of the crack length, a, vs. the COD for both the outer diameter (OD) and inner diameter (ID) sides of the curved specimen from the finite element results, along with the prediction of a using the ASTM equation (1) above is shown in Figure 7. The figure shows the results for the X65 geometry; however, the results for the X100 geometries were similar.…”

Section: Comparison To Bs 7910 Design Standardmentioning

confidence: 99%

“…Fatigue properties, included in the integrity management of U.S pipeline regulations and international design standards, must be taken into consideration in the safety assessment of oil and natural gas pipelines. Fluctuations in internal operating pressure and external loads can cause fatigue crack growth [1]. Appropriate fatigue-crack-growth rate (FCGR) testing must be performed in order to accurately use these properties in the design of the pipelines.…”

Section: Introductionmentioning

confidence: 99%

“…To prevent crack closure and other nonlinearities from influencing the compliance measurement, the automated test software excludes the top 10 % and bottom 20 % of the COD vs. load curve to measure the compliance, B. Furthermore, to average possible hysteresis effects, the compliance was measured from both the loading and unloading portions of the cycle [1,9]. An analysis of the effect the compliance expressions have on the results will be analyzed later.…”

mentioning

confidence: 99%

“…Flattening would introduce plastic strain effects that may influence the FCGR behavior. To accommodate the curved specimens, special adaptor blocks were machined so the specimens could be mounted in the hydraulic grips [1]. The C(T) specimens dimensions are shown in Figure 2.…”

mentioning

confidence: 99%

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Effects of Specimen Geometry on Fatigue-Crack Growth Rates in Pipeline Steels

Treinen

Darcis

McColskey

et al. 2008

2008 7th International Pipeline Conference, Volume 3

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The effects of specimen geometry on the fatigue crack growth rates (FCGR) in API X65 and X100 pipeline steels were explored by use of the middle tension and compact tension specimen geometries. It was found that the specimen type has little influence on the stage II linear fatigue crack growth region for these steels. Furthermore, the FCGR behavior in the longitudinal and transverse directions was found to be nearly identical for both steels. Also of interest was a comparison of the FCGR results to the BS 7910 design curves, which showed a discrepancy between the results and the standard only at low delta K levels. A finite element analysis of the compliance relationships used to predict the crack lengths during testing of both specimen types revealed that the expression for both the middle tension specimen and the compact tension specimen were found to be valid. Although the curved geometry of the middle tension specimen caused slightly different compliance results, these differences did not appear to affect the FCGR results.

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Fracture-Toughness and Fatigue Crack Growth Evaluation in the Transversal Direction of the Longitudinal Weld of an API X52 Steel Pipeline

Angeles-Herrera

Albiter

Cuamatzi-Meléndez

et al. 2018

Journal of Testing and Evaluation

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In this paper, the fracture-toughness and fatigue crack growth rates of the deposited seam weld on the longitudinal pipeline API 5L X52 were evaluated. The study was performed with nonstandard curved specimens, which were machined in the transversal direction of the seam weld with a crack-initiating notch aligned perpendicular to the direction of the deposited seam weld metal. The fractographic analysis showed that the low fracture-toughness of the weld can be attributed to the the existence of elements capable of nucleating brittle fracture and the fact that the intrinsic porosity in the transversal direction provided a favorable crack path for separating the fracture plane, resulting in low fracture-toughness values. Finally, the resistance decrease with respect to the fatigue crack growth was attributed to the small grain size because of the effect of roughness-induced crack closure as well as the interaction of the crack and the inherent porosity.

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Fatigue Crack Growth Rates in Six Pipeline Steels

Cited by 4 publications

References 5 publications

Fatigue Pre-Cracking Curved Wide Plates in Bending

Fatigue Pre-Cracking Curved Wide Plates in Bending

Effects of Specimen Geometry on Fatigue-Crack Growth Rates in Pipeline Steels

Fracture-Toughness and Fatigue Crack Growth Evaluation in the Transversal Direction of the Longitudinal Weld of an API X52 Steel Pipeline

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