Experimental Validation of Constraint Effects on Toughness Test of Pipeline Girth Welds

Limit Load and Reference Stress for Curved Wide Plates

2010 8th International Pipeline Conference, Volume 1 ◽

10.1115/ipc2010-31290 ◽

2010 ◽

Author(s):

Stijn Hertele´ ◽

Wim De Waele ◽

Rudi Denys ◽

Jeroen Van Wittenberghe ◽

Matthias Verstraete

Keyword(s):

Experimental Validation ◽

Limit Load ◽

Plastic Collapse ◽

Test Results ◽

Finite Element Analyses ◽

Flat Plates ◽

Stress Equation ◽

Reference Stress ◽

Plate Curvature ◽

Girth Welds

Curved wide plates are a valuable tool in the assessment of defective pipeline girth welds under tension. Throughout the years, Laboratory Soete collected an extensive database of curved wide plate test results. In an effort to investigate these results through FAD analysis, the authors recently developed a reference stress equation for curved plates. The approach followed is similar to the development of the Goodall and Webster equation for flat plates. This paper elaborates finite element analyses of the equation’s capability to predict plastic collapse. It is found that, although overestimated, the influence of plate curvature is correctly predicted in a qualitative way. For all simulations, the curved plate reference stress equation produced conservative estimations. This indicates that the proposed equation is suited to safely predict the plastic collapse of defective pipeline girth welds. An experimental validation is underway.

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Inherent possibilities and limitations of finite element modelling of defective girth welds

International Journal Sustainable Construction & Design ◽

10.21825/scad.v1i1.20411 ◽

2010 ◽

Vol 1 (1) ◽

pp. 127-135

Author(s):

Stijn Hertele ◽

Wim De Waele ◽

Rudi Denys ◽

Matthias Verstraete

Keyword(s):

Finite Element ◽

Crack Growth ◽

Experimental Research ◽

Finite Element Modelling ◽

Experimental Validation ◽

Stable Crack Growth ◽

Worst Case ◽

Element Modelling ◽

Numerical Research ◽

Girth Welds

Welds unavoidably show defects, which can negatively affect the integrity of the entire structureand, worst case, result in a failure. Defects of a considerable size should therefore be detected, assessedand, if necessary, repaired. The assessment of a defect requires a procedure which allows a conservativeestimation of the acceptability of the defect. To develop such procedure, both experimental and numericalresearch is performed. This paper describes the inherent possibilities and limitations of numerical researchthrough finite element modelling, as compared to experimental research. Summarizing all arguments, itbecomes clear that numerical research is a highly powerful tool, but a thorough experimental validation is ofparamount importance. Moreover, some specific weld-related problems are highly difficult to address,namely the presence of stable crack growth and material heterogeneity. More research is needed toachieve a description of these phenomena, under a set of conservative assumptions.

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Weld Strength Mismatch in Strain Based Flaw Assessment: Which Definition to Use?

Journal of Pressure Vessel Technology ◽

10.1115/1.4025343 ◽

2013 ◽

Vol 135 (6) ◽

Cited By ~ 5

Author(s):

Stijn Hertelé ◽

Wim De Waele ◽

Rudi Denys ◽

Matthias Verstraete ◽

Koen Van Minnebruggen ◽

...

Keyword(s):

Tensile Strength ◽

Ultimate Tensile Strength ◽

Driving Force ◽

Experimental Validation ◽

Weld Strength ◽

Crack Driving Force ◽

Strain Capacity ◽

Strength Based ◽

Key Factor ◽

Girth Welds

Weld strength mismatch is a key factor in the strain based assessment of flawed girth welds under tension. A strength overmatching weld shields potential flaws within the weld itself from remotely applied deformations and consequently reduces crack driving force. Although this effect has been recognized for decades, different weld strength overmatch definitions exist, and it is not yet fully established which of those is most relevant to a strain based flaw assessment. In an effort to clarify this unsolved question, the authors have performed a large series of parametric finite element analyses of curved wide plate tests. This paper provides an experimental validation of the model and subsequently discusses representative results. It is found that crack driving force is influenced by the shape of the pipe metals' stress–strain curves, which influences the representativeness of two common mismatch definitions (based on yield strength and on ultimate tensile strength). Effects of strength mismatch on strain capacity of a flawed girth weld are best described on the basis of a flow stress, defined as the average of yield and ultimate tensile strength. Based on the observations, a framework for a new strain capacity equation is proposed.

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Toughness of X80 Grade Pipe Steel Girth Welds by Curved Wide Plate Testing

Materials Science Forum ◽

10.4028/www.scientific.net/msf.850.873 ◽

2016 ◽

Vol 850 ◽

pp. 873-880 ◽

Cited By ~ 1

Author(s):

Deng Zun Yao ◽

Long Zhang ◽

Yu Ran Fan ◽

Tian Qi Wang ◽

Yan Zhou

Keyword(s):

Pipe Steel ◽

Pipeline Steel ◽

Test Methods ◽

Test Results ◽

Single Edge ◽

Toughness Test ◽

The Difference ◽

Steel Welds ◽

Girth Welds

To confirm pipeline designs and validate the weld toughness, extensively works of Curved Wide Plate (CWP) test methods was carried out. The method of Two Clip Gauge-CTOD was firstly introduced in CWP test in this paper. The test results of CWP analyzed by Two Clip Gauge-CTOD method and Compliance—J method was compared. The CTOD-R curves achieved by these methods showed the good consistence with each other. Furthermore, the difference of the test results among SENB(single edge-notched bend), SENT(single edge-notched tensile) and CWP was discussed. It shows that the toughness obtained by SENB is relatively conservative, and CWP and SENT are recommend to be chosen for pipeline steel welds toughness test.

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Weld Strength Mismatch in Strain Based Flaw Assessment: Which Definition to Use?

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2012-78306 ◽

2012 ◽

Cited By ~ 1

Author(s):

Stijn Hertelé ◽

Wim De Waele ◽

Rudi Denys ◽

Matthias Verstraete ◽

Koen Van Minnebruggen ◽

...

Keyword(s):

Tensile Strength ◽

Ultimate Tensile Strength ◽

Driving Force ◽

Experimental Validation ◽

Weld Strength ◽

Crack Driving Force ◽

Strain Capacity ◽

Strength Based ◽

Key Factor ◽

Girth Welds

Weld strength mismatch is a key factor in the strain based assessment of flawed girth welds under tension. A strength overmatching weld shields potential flaws within the weld itself from remotely applied deformations and consequently reduces crack driving force. Although this effect has been recognized for decades, different weld strength overmatch definitions exist and it is not yet fully established which of those is most relevant to a strain based flaw assessment. In an effort to clarify this unsolved question, the authors have performed a large series of parametric finite element analyses of curved wide plate tests. This paper provides an experimental validation of the model and subsequently discusses representative results. It is found that crack driving force is influenced by the shape of the pipe metals’ stress-strain curves, which influences the representativeness of two common mismatch definitions (based on yield strength and on ultimate tensile strength). It can be concluded from further observations that effects of strength mismatch on strain capacity of a flawed girth weld are best described on the basis of a flow stress, defined as the average of yield and ultimate tensile strength. Based on the observations, a framework for a new strain capacity equation is proposed.

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