Analysis of ductile tearing of pipeline-steel in single edge notch tension specimens

As the demand for fossil fuels increases, pipelines are constructed in inhospitable areas. Underthese conditions, not only the strength but also the deformability of the pipelines becomes crucial. A strainbased design (SBD) procedure needs to be established. Traditional stress based approaches to evaluatedefect tolerance lead to conservative predictions. There is a need to accurately define the fracturetoughness of the pipeline steel and assess the criticality of weld defects under strain based conditions. Thispaper focuses on the implementation of the unloading compliance method to determine stable crackgrowth. The standardized test procedure described in ASTM E1820 is applied. This method is a handy toolto obtain the J-resistance curves which can forecast ductile failure in pipeline girth welds. Preliminaryexperiments have been performed on Single Edge Notch Bend (SENB) specimens of plain pipe metal.Using the implemented procedure, it was possible to obtain a good fit between calculated and measuredcrack size. The most important result is the smoothness of the calculated crack growth and the rathermonotonic increase of crack size. Since testing on SENB is well known to provide conservativemeasurements, Single Edge Notch Tension (SENT) specimens will be evaluated in future work

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Fracture Control — Offshore Pipelines: Experimental Studies on the Effect of Crack Depth and Asymmetric Geometries on the Ductile Tearing Resistance

24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 3 ◽

10.1115/omae2005-67532 ◽

2005 ◽

Cited By ~ 11

Author(s):

Ba˚rd Nyhus ◽

Erling O̸stby ◽

Hans Olav Knagenhjelm ◽

Scott Black ◽

Per Arne Ro̸stadsand

Keyword(s):

Fracture Toughness ◽

Crack Depth ◽

Experimental Studies ◽

Single Edge ◽

Offshore Pipelines ◽

Ductile Tearing ◽

Single Edge Notch ◽

Edge Notch ◽

Fracture Control ◽

Tearing Resistance

Engineering critical assessment of offshore pipelines is usually very conservative if standardized single edge notch bend (SENB) specimens are used for the fracture mechanics testing. It is commonly accepted that the fracture toughness is dependent on the geometry constraint at the crack tip. The standardized SENB specimens have a high geometry constraint, and give lower bound fracture toughness for all geometries. For circumferential flaws in pipes the single edge notch tension (SENT) specimens is taken more into use, to establish more correct fracture toughness for the pipe in question. In this paper the effect of crack depth, misalignment and different wall thicknesses in SENT specimens have been studied. In addition the effect of crack depth and internal pressure in pipes have been studied with FE simulations.

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Specimen thickness effect on the property of hydrogen embrittlement in single edge notch tension testing of high strength pipeline steel

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2018.06.118 ◽

2018 ◽

Vol 43 (32) ◽

pp. 15575-15585 ◽

Cited By ~ 11

Author(s):

Yizhe Li ◽

Baoming Gong ◽

Xiaogang Li ◽

Caiyan Deng ◽

Dongpo Wang

Keyword(s):

Hydrogen Embrittlement ◽

Pipeline Steel ◽

High Strength ◽

Thickness Effect ◽

Specimen Thickness ◽

Single Edge ◽

Single Edge Notch ◽

Tension Testing ◽

Edge Notch

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Modelling the Variability and the Anisotropic Behaviour of Crack Growth in SLM Ti-6Al-4V

Materials ◽

10.3390/ma14061400 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1400

Author(s):

Rhys Jones ◽

Calvin Rans ◽

Athanasios P. Iliopoulos ◽

John G. Michopoulos ◽

Nam Phan ◽

...

Keyword(s):

Crack Growth ◽

The United States ◽

Fatigue Threshold ◽

Growth Equation ◽

Single Edge ◽

Test Program ◽

Large Variability ◽

Single Edge Notch ◽

Anisotropic Behaviour ◽

Edge Notch

The United States Air Force (USAF) Guidelines for the Durability and Damage Tolerance (DADT) certification of Additive Manufactured (AM) parts states that the most difficult challenge for the certification of an AM part is to establish an accurate prediction of its DADT. How to address this challenge is the focus of the present paper. To this end this paper examines the variability in crack growth in tests on additively manufactured (AM) Ti-6Al-4V specimens built using selective layer melting (SLM). One series of tests analysed involves thirty single edge notch tension specimens with five build orientations and two different post heat treatments. The other test program analysed involved ASTM standard single edge notch specimens with three different build directions. The results of this study highlight the ability of the Hartman–Schijve crack growth equation to capture the variability and the anisotropic behaviour of crack growth in SLM Ti-6Al-4V. It is thus shown that, despite the large variability in crack growth, the intrinsic crack growth equation remains unchanged and that the variability and the anisotropic nature of crack growth in this test program is captured by allowing for changes in both the fatigue threshold and the cyclic fracture toughness.

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