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Research Papers: Materials and Fabrication

Overview of NIST Activities on Subsize and Miniaturized Charpy Specimens: Correlations With Full-Size Specimens and Verification Specimens for Small-Scale Pendulum Machines

[+] Author and Article Information
Enrico Lucon

National Institute of Standards and Technology,
Applied Chemicals and Materials Division,
325 Broadway,
Boulder, CO 80305
e-mail: enrico.lucon@nist.gov

Chris N. McCowan

National Institute of Standards and Technology,
Applied Chemicals and Materials Division,
325 Broadway,
Boulder, CO 80305
e-mail: chrismccowan81@gmail.com

Raymond L. Santoyo

National Institute of Standards and Technology,
Applied Chemicals and Materials Division,
325 Broadway,
Boulder, CO 80305
e-mail: raymond.santoyo@nist.gov

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received July 26, 2015; final manuscript received January 4, 2016; published online February 8, 2016. Assoc. Editor: Osamu Watanabe.This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Pressure Vessel Technol 138(3), 031405 (Feb 08, 2016) (8 pages) Paper No: PVT-15-1173; doi: 10.1115/1.4032474 History: Received July 26, 2015; Revised January 04, 2016

NIST in Boulder, CO investigated the correlations between impact test results obtained from standard, full-size Charpy V-notch (CVN) specimens and specimens with reduced thickness (subsize Charpy V-notch specimens (SCVN)) or reduced or scaled cross section dimensions (miniaturized Charpy V-notch specimens (MCVN)). A database of instrumented impact test results was generated from four line pipe steels: two quenched alloy steels, a tempered alloy steel, and a 18 Ni maraging steel. Correlations between specimen types were established and compared with the previously published relationships, considering absorbed energy (KV), ductile-to-brittle transition temperature (DBTT), and upper shelf energy (USE). Acceptable correlations were found for the different parameters, even though the uncertainty of predictions appears exacerbated by the expected significant experimental scatter. Furthermore, we report on the development of MCVN specimens for the indirect verification of small-scale pendulum machines (with potential energies between 15 J and 50 J), which cannot be verified with full-size verification specimens. Small-scale pendulum machines can now be verified at room temperature with certified reference specimens of KLST type (3 mm × 4 mm × 27 mm), supplied by NIST at three certified KV levels (low energy (LL), 1.59 J; high energy (HH), 5.64 J; and super-high (SH) energy, 10.05 J). These specimens can also be used to verify the performance of instrumented Charpy strikers through certified maximum force values. Certified reference values for both KV and maximum force were established by means of an interlaboratory comparison (Round-Robin), which involved nine qualified and experienced international laboratories.

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References

Figures

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Fig. 3

DBTTKV values calculated for X52 and LL141

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Fig. 4

Comparison between DBTTs calculated for LL141, HH143, and SH38

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Fig. 5

Transition temperature shifts between CVN and SCVN/MCVN specimens, as a function of specimen cross section

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Fig. 6

Calculated transition temperature shifts as a function of specimen thickness, and comparison with Eqs. (2) and (3)

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Fig. 7

ΔT0.25J/mm2 and ΔT0.5J/mm2 versus specimen thickness, and comparison with Eqs. (2) and (3)

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Fig. 8

Comparison between ΔDBTTKV, ΔDBTTLE, and ΔFATT50

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Fig. 9

Comparison between ΔT0.25J/mm2 and ΔT0.5J/mm2

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Fig. 10

Filtered NIST database of transition temperature shifts, and comparison with Eqs. (2) and (3)

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Fig. 11

Filtered NIST database of transition temperature shifts as a function of ligament cross section

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Fig. 12

Energy densities for CVN, SCVN, and MCVN specimens

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Fig. 13

Energy density ratio as a function of SCVN/MCVN cross-sectional area

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Fig. 14

Geometrical and empirical NFs for SCVN and MCVN specimens

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Fig. 15

Comparison between Eq.(12) and NIST results from CVN and KLST tests of line pipe steels

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