Research Papers: Design and Analysis

Failure Prediction of Curved Wide Plates Using the Strain-Based Failure Assessment Diagram With Correction for Constraint and Notch Radius

[+] Author and Article Information
Anthony Horn

Warrington WA3 6GB, UK
e-mail: anthony.horn@amec.com

Mikhail Trull

Swinden Technology Centre,
Tata Steel RD&T,
Moorgate, Rotherham,
South Yorkshire S60 3AR, UK
e-mail: michael.trull@tatasteel.com

Stijn Hertelé

Soete Laboratory,
Ghent University,
Technologiepark Zwijnaarde 903,
Zwijnaarde 9052, Belgium
e-mail: stijn.hertele@ugent.be

1Address at the time of performing this work: Tata Steel RD&T, South Yorkshire S60 3AR, UK.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received August 26, 2013; final manuscript received September 8, 2014; published online November 21, 2014. Assoc. Editor: Xian-Kui Zhu.

J. Pressure Vessel Technol 137(2), 021208 (Apr 01, 2015) (10 pages) Paper No: PVT-13-1146; doi: 10.1115/1.4028560 History: Received August 26, 2013; Revised September 08, 2014; Online November 21, 2014

The strain-based failure assessment diagram (SB-FAD) has been developed for predicting failure from flaws in components subjected to high plastic strains. In this paper, a combined numerical and experimental approach is used to apply the SB-FAD to predict failure from a series of API 5L grades X80 and X100 curved wide plate (CWP) specimens with shallow notches machined into the pipe girth weld. For the CWP specimens tested in this work, the SB-FAD in its unmodified form resulted in over-conservative predictions of failure. This is attributed to the SB-FAD assuming high constraint conditions and the presence of a sharp fatigue crack, whereas the CWP specimens tested in this work were low constraint and contained a shallow machined notch without fatigue cracks. A modification of the SB-FAD is then proposed to account for nonsharp defects loaded to high plastic strains under conditions of low constraint. The resulting predictions of the modified SB-FAD show significantly reduced conservatism compared to the unmodified SB-FAD.

Copyright © 2015 by ASME
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Fig. 1

CWP geometry and instrumentation used at Tata Steel. (a) Schematic. (b) Photo showing specimen (without cooling panels).

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Fig. 2

All five CWP results tested at Tata Steel. All tests at −20 °C unless otherwise stated.

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Fig. 3

FE model of the CWP test showing (a) overall model, (b) mesh near the notch mouth, and (c) notch tip mesh

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Fig. 4

Example of a stress–strain curve used as input to FE analysis

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Fig. 5

Validation of FE results against CWP test data (load versus global LVDT strain). All tests were performed at −20 °C.

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Fig. 6

Validation of FE results against CWP test data (CMOD versus global LVDT strain). All tests were performed at −20 °C.

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Fig. 7

Comparison of CTOD and CMOD from FE model and calculated from clip gage displacements using Eq. (4) (X80AC test data)

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Fig. 8

Options 1–3 failure assessment loci for the X80 and X100 CWPs

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Fig. 9

Failure prediction of Tata Steel CWP tests using Option 3 SB-FAD in its unmodified form (Kmat defined at Pf = 50%)

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Fig. 10

Failure prediction of Tata Steel CWP test results using modified SB-FAD approach (Kmat defined at Pf = 50%). In each graph, the lower curve represents the loading line, whereas the upper curve represents the failure locus.

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Fig. 11

All CWP results assessed using modified SB-FAD approach (Kmat defined at Pf = 50%)




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