Research Papers: Materials and Fabrication

Framework for Key Influences on Tensile Strain Capacity of Flawed Girth Welds

[+] Author and Article Information
Stijn Hertelé

Soete Laboratory,
Ghent University,
Technologiepark Zwijnaarde 903,
Zwijnaarde 9052, Belgium
e-mail: Stijn.Hertele@UGent.be

Rudi Denys

Soete Laboratory,
Ghent University,
Zwijnaarde 9052, Belgium
e-mail: Rudi.Denys@UGent.be

Anthony Horn

AMEC Foster Wheeler,
Warrington, Cheshire WA3 6XF, UK
e-mail: Anthony.Horn@amecfw.com

Koen Van Minnebruggen

Soete Laboratory,
Ghent University,
Zwijnaarde 9052, Belgium
e-mail: Koen.VanMinnebruggen@UGent.be

Wim De Waele

Soete Laboratory,
Ghent University,
Zwijnaarde 9052, Belgium
e-mail: Wim.DeWaele@UGent.be

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received August 22, 2013; final manuscript received January 7, 2015; published online February 23, 2015. Assoc. Editor: Hardayal S. Mehta.

J. Pressure Vessel Technol 137(4), 041409 (Aug 01, 2015) (9 pages) Paper No: PVT-13-1141; doi: 10.1115/1.4029589 History: Received August 22, 2013; Revised January 07, 2015; Online February 23, 2015

A key influence factor in the strain-based assessment of pipeline girth weld flaws is weld strength mismatch. Recent research has led to a framework for tensile strain capacity as a function of weld flow stress (FS) overmatch. This framework is built around three parameters: the strain capacity of an evenmatching weldment, the sensitivity of strain capacity to weld FS overmatch, and the strain capacity at gross section collapse (GSC). A parametric finite element study of curved wide plate (CWP) tests has been performed to identify the influence of various characteristics on each of these three parameters. This paper focuses on flaw depth, tearing resistance of the weld, stress–strain behavior of the base metal, and weld geometry. Influences of these characteristics are mostly found to be limited to one or two of the three framework parameters. A preliminary structure is proposed for equations that further develop the strain capacity framework.

Copyright © 2015 by ASME
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Fig. 1

Graphical description of strain capacity equation (2), based on weld FS overmatch (Eq. (1)) [5].

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Fig. 2

Longitudinal strain distributions in curved medium wide plate specimens obtained through digital image correlation, indicating (a) NSC and (b) GSC [7]

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Fig. 3

Graphical explanation of the mapping approach for incorporation of (un)stable crack growth

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Fig. 4

Two weld geometries were considered: a narrow gap weld A and a wider beveled weld B

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Fig. 5

Graphical representation of the UGent stress–strain model for line pipe steels [16]

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Fig. 6

Δε is related to Y/T and em

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Fig. 7

This study covers three different weld metal CTOD-R curves

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Fig. 8

Three example strain capacity curves confirm the bilinear nature of the relation between emax and OMFS

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Fig. 9

The tensile strain capacity of an evenmatching weldment, emax,0, is influenced by flaw depth

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Fig. 10

The sensitivity of strain capacity to weld FS overmatch, C, is influenced by flaw depth

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Fig. 11

The effect of weld geometry on tensile strain capacity is mostly reflected in C

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Fig. 12

Weld geometry has a pronounced effect on the strain capacity's sensitivity to FS overmatch

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Fig. 13

Weld metal CTOD-R behavior influences emax,0

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Fig. 14

Base metal stress–strain behavior affects emax,0 and emax,GSC

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Fig. 15

Two base metal stress–strain curves with pronounced differences in em and Δε

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Fig. 16

Decreasing Δε tends to increase emax,0. This trend is prone to substantial scatter.

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Fig. 17

Decreasing Δε tends to increase C




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