Fracture Toughness Estimation for Pipeline Girth Welds

2002 ◽  
Author(s):  
Henryk G. Pisarski ◽  
Colin M. Wignall
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Specimen Geometry ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch ◽  
Loading Modes ◽  
Girth Welds ◽  
The Relationship ◽  
Single Edge Notch Bend

The relationship between fracture toughness estimated using standard single edge notch bend (SENB), single edge notch tension (SENT) test specimens and fracture toughness associated with a circumferential flaw in a pipe girth weld is explored in terms of constraint using the Q parameter. It is shown that in the elastic-plastic regime, use of standard deeply notched SENB specimens provides a conservative assessment of fracture toughness, for both weld metal and HAZ, because of the high constraint associated with this specimen geometry. Use of specimen geometries and loading modes associated with lower constraint (e.g. SENT and shallowed notched SENB specimens), allow for improved estimates of fracture toughness to be made that are appropriate for the assessment of circumferential flaws in pipe girth welds. Recommendations are given on the specimen designs and notch orientations to be employed when evaluating weld metal and HAZ fracture toughness.

Effects of Strain Rate on Fracture Toughness in Sour Environment

2010 ◽  
Author(s):  
Wen Guo Yuan ◽  
Da Qin Xu ◽  
You You Wu ◽  
Jens P. Tronskar
Keyword(s):  
Fracture Toughness ◽  
Strain Rate ◽  
Strain Rate Range ◽  
J Integral ◽  
Single Edge ◽  
Fracture Toughness Testing ◽  
Single Edge Notch ◽  
Edge Notch ◽  
Toughness Testing ◽  
Girth Welds

Fracture toughness testing in sour environment using Single Edge Notch Tensile (SENT) and Single Edge Notch Bend (SENB) specimens has been developed and applied by authors’ laboratory for Engineering Critical Assessment (ECA) of pipeline girth welds. The method of testing and application of fracture toughness result for ECAs of pipeline girth welds for sour service has been presented at a previous OMEA conference (paper OMAE2009-79305). The current paper presents the results of further experimental work carried out to evaluate the effect of strain rate on the fracture toughness value. A series of fracture toughness tests using SENT specimens was carried out in artificial brine sour environment (NACE solution “A” saturated with H2S) at ambient temperature. For comparison, the result from test in air condition are also presented and discussed. Following the test, the J-integral and the CTOD values were calculated and assessed. As expected, the results show significant effect of strain rate on the J integral value and the CTOD, especially for the strain rate range between 10−6/s to 10−7/s. Further experiments and studies are suggested to establish appropriate procedures and guidelines for selection of suitable strain rates for sour environment fracture toughness testing of pipeline girth welds.

Development of Test Guidance for Single Edge Notch Bend Fracture Toughness Specimens Containing Notches Instead of Fatigue Pre-Cracks

2015 ◽  
Author(s):  
Anthony J. Horn ◽  
Peter J. Budden
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Fatigue Cracks ◽  
Single Edge ◽  
Integrity Assessment ◽  
Single Edge Notch ◽  
Notched Specimens ◽  
Edge Notch ◽  
Cracked Specimens ◽  
Single Edge Notch Bend

Structural integrity assessment codes such as R6 and BS7910 provide guidance on the assessment of flaws that are assumed to be infinitely sharp. In many cases, such as fatigue cracks, this assumption is appropriate, however it can be pessimistic for flaws that do not have sharp tips such as lack of fusion, porosity or mechanical damage. Several methods have been proposed in the literature to quantify the additional margins that may be present for non-sharp defects compared to the margins that would be calculated if the defect were assumed to be a sharp crack. A common feature of these methods is the need to understand how the effective toughness, characterised using the J-integral for a notch, varies with notch acuity. No comprehensive guidance currently exists for obtaining J experimentally from specimens containing notches, hence the typical approach is to use equations intended for pre-cracked specimens to calculate J for notched specimens. This paper presents a comprehensive set of test guidance for calculating J from Single Edge Notch Bend (SENB) fracture toughness specimens containing notches instead of fatigue pre-cracks. This has been achieved using 3D Finite Element Analyses to quantify the accuracy of formulae intended for pre-cracked specimens in fracture toughness testing standards ASTM E1820, BS7448-1 and ESIS P2-92 when applied to specimens containing notches. The paper quantifies the accuracy of these equations for notched SENB specimens and identifies the conditions under which the equations can lead to inaccurate measurement of J for notched specimens.

SENT Specimens an Alternative to SENB Specimens for Fracture Mechanics Testing of Pipelines

2003 ◽  
Author(s):  
Ba˚rd Nyhus ◽  
Mario Loria Polanco ◽  
Oddvin O̸rjasæther
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Assessment Procedure ◽  
Plastic Collapse ◽  
Single Edge ◽  
Tension Specimen ◽  
Single Edge Notch ◽  
Defect Assessment ◽  
Edge Notch ◽  
Single Edge Notch Bend

During installation operations offshore pipes are often strained beyond yielding. Due to the high loading condition and the high costs of these operations it is important with accurate defect assessment analysis to avoid delays caused by unnecessary repairs or failure because of flaws that should have been detected and repaired. There is therefore a need for an accurate assessment procedure that can be a tool for defect assessment analysis for this application. It is commonly accepted that the fracture toughness is dependent on the geometry constraint at the crack tip. The traditional single edge notch bend (SENB) specimens have a high geometry constraint, and give lower bound fracture toughness for all geometries. For reeling operations these fracture toughness values are often too low to be used in defect assessment of reeling operations. The same is the assumption of plastic collapse when the net section stress is equal to the average between the yield strength and tensile strength. In this paper, the single edge notch tension specimen (SENT) is presented as an alternative fracture mechanics specimen. This specimen has a geometry constraint that is much closer to flaws in pipes than SENB specimens, which will give more realistic fracture properties of the pipe. In the procedure for defect assessments we present, both the fracture toughness and plastic collapse properties are taken from testing of SENT specimens. FE simulations and full scale testing verify the procedure.

Comparison of Fatigue Crack Growth Rates Between Different Specimen Geometries

2021 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Matthew Doré
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Literature Review ◽  
Crack Growth ◽  
Compact Tension ◽  
Specimen Geometry ◽  
Single Edge ◽  
Single Edge Notch ◽  
Advantages And Disadvantages ◽  
Edge Notch

Abstract Most engineering components are subjected to cyclic loading in service and design against fatigue failure is often a key consideration in design. For fracture mechanics fatigue analysis, fatigue crack growth (FCG) tests are often required to determine the relevant Paris power law parameters for the material under the environment concerned. Standards allow use of different specimen geometries for FCG tests such as compact tension (CT), centre crack tension (CCT), single edge notch bend (SENB) and single edge notch tension (SENT). However, when selecting specimen geometry for fatigue crack growth rate (FCGR) testing, there is often doubt about which specimen geometry is more appropriate and whether they give similar FCGR. There is limited work to compare the FCGR between different specimen geometries. This paper first briefly introduces the guidance on FCG test specimen geometries in standards and compares the advantages and disadvantages of these specimen geometries. A comprehensive literature review is carried out to compare the FCGR data between different specimen geometries. FCGR tests are conducted on SENB, SENT and CCT specimens of C-Mn steel to investigate any effects of specimen symmetry/asymmetry and crack constraint on FCGR. Based on the literature review and test data, it is concluded that FCGR is independent of the specimen geometries examined.

Fracture toughness of Si3N4 fibers: A combined methodology based on single-edge notch tension and micropillar splitting

2018 ◽  
Vol 44 (17) ◽  
pp. 22036-22040
Author(s):  
Xun Sun ◽  
Haitao Liu ◽  
Lingwei Yang ◽  
Ru Jiang ◽  
Haifeng Cheng
Keyword(s):  
Fracture Toughness ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch
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