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Research Papers

Evaluation of Two Low-Constraint Toughness Test Methods in a Single Specimen

[+] Author and Article Information
Dong-Yeob Park

CanmetMATERIALS,
Natural Resources Canada,
Calgary, AB T2L2A7, Canada
e-mail: dopark@nrcan.gc.ca

Jean-Philippe Gravel

CanmetMATERIALS,
Natural Resources Canada,
Calgary, AB T2L2A7, Canada
e-mail: jegravel@nrcan.gc.ca

Muhammad Arafin

CanmetMATERIALS,
Natural Resources Canada,
Calgary, AB T2L2A7, Canada
e-mail: marafin@nrcan.gc.ca

Jie Liang

CanmetMATERIALS,
Natural Resources Canada,
Hamilton, ON L8P 0A5, Canada
e-mail: jliang@nrcan.gc.ca

C. Hari Manoj Simha

CanmetMATERIALS,
Natural Resources Canada,
Hamilton, ON L8P 0A5, Canada
e-mail: csimha@nrcan.gc.ca

1Corresponding author.

Contributed by the Materials Division of ASME for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received May 9, 2014; final manuscript received September 24, 2014; published online October 23, 2014. Assoc. Editor: Hareesh Tippur.

J. Eng. Mater. Technol 137(1), 011003 (Oct 23, 2014) (9 pages) Paper No: MATS-14-1100; doi: 10.1115/1.4028728 History: Received May 09, 2014; Revised September 24, 2014

In previous studies, the single- and double-clip gauge methods were successfully consolidated in a single-edge notched tension (SE(T)) single specimen so that crack tip opening displacement (CTOD) values obtained from both SE(T) methods could be compared under identical test conditions. The current study investigated the effect of unloading compliance crack size equations on resistance curves obtained from both gauging methods combined in a single specimen. It was found that the unloading compliance crack size equations of Cravero and Ruggieri and the single clip gauge method predict crack sizes well within approximately 2% error in average. Two CTOD-resistance curves obtained from both gauging methods produce approximately the same results until peak loads, and thereafter the curves deviate. The results obtained from the double clip gauge method are consistently higher than those from the single clip gauge, although the difference between two resistance curves is reduced when the same unloading compliance crack size prediction procedure is used. This observation is very important within the framework of engineering critical assessment (ECA) and defect assessment procedures. An “apparent” higher resistance curve will generate larger tolerable defects thereby reducing the conservatism of an ECA analysis.

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References

Figures

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Fig. 1

Engineering stress versus strain curves of base and weld metals from (a) 13.4 mm and (b) 17.8 mm thick pipes and girth welds

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Fig. 2

Knife-edge fixtures: (a) photo of the fixtures on a specimen and (b) illustration of the side view

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Fig. 5

Comparisons of measured and unloading-compliance predicted crack size from both 17.8 and 13.4 mm thick pipes using original unloading compliance equations

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Fig. 6

Representative fracture surfaces of SE(T) specimens from 17.8 mm thick pipe girth weld. Scale graduations equal 1.0 mm (from Ref. [10]). (a) Weld metal, a0/W = 0.35 and (b) HAZ, a0/W = 0.35.

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Fig. 7

Comparisons of measured and unloading-compliance predicted crack size from both 17.8 and 13.4 mm thick pipes using Cravero and Ruggieri's equation and Eq. (4) for aoq calculations

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Fig. 8

CTOD-resistance curves from single- and double-clip gauge SE(T) methods for the 17.8 mm thick pipe specimens using Cravero's equation for a/W: (a) HAZ and (b) weld metal

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Fig. 9

CTOD-resistance curves from single- and double-clip-gauge SE(T) methods for the (a) 17.8 mm and (b) 13.4 mm thick pipe specimens using Cravero and Ruggieri's unloading compliance and rotation correction equations (Eqs. (9) and (2))

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Fig. 10

Comparisons of estimated (δM) with measured (V) CMODs

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Fig. 11

Unloading compliance comparisons from Ref. [9]

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Fig. 12

Comparisons of crack size estimations using δM and V. Cravero and Ruggieri's unloading compliance equation was used.

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Fig. 13

CTOD-resistance curves from single- and double-clip gauge SE(T) methods for the (a) 17.8 mm and (b) 13.4 mm thick pipe specimens using Cravero and Ruggieri's unloading compliance, rotation correction equations, and predicted CMOD, δM

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Fig. 4

CTOD-resistance curves from single- and double-clip gauge SE(T) methods for the (a) 17.8 mm and (b) 13.4 mm thick pipe specimens using the original unloading compliance crack size equations

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