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Technical Brief

A Basis for Selecting the Most Appropriate Small Specimen Creep Test Type

[+] Author and Article Information
T. H. Hyde, C. J. Hyde, W. Sun

Department of Mechanical,
Materials and Manufacturing Engineering,
The University of Nottingham,
University Park,
Nottingham NG7 2RD, UK

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received August 23, 2012; final manuscript received October 24, 2013; published online January 7, 2014. Assoc. Editor: Osamu Watanabe.

J. Pressure Vessel Technol 136(2), 024502 (Jan 07, 2014) (6 pages) Paper No: PVT-12-1139; doi: 10.1115/1.4025864 History: Received August 23, 2012; Revised October 24, 2013

Many components in conventional and nuclear power plant, aero-engines, chemical plant etc., operate at temperatures which are high enough for creep to occur. These include plain pipes, pipe bends, branched pipes etc., the manufacture of such components may also require welds to be inserted in them. In most cases, only nominal operating conditions (i.e., pressure, temperatures, system load, etc.) are known and hence precise life predictions are not possible. Also, the proportion of life consumed will vary from position to position within a component and the plant. Hence, nondestructive techniques are adopted to assist in making decisions on whether to repair, continue operating or scrap certain components. One such approach is to use scoop samples removed from the components to make small creep test specimens, i.e., sub-size uniaxial creep test specimens, impression creep test specimens, small punch creep test specimens, and small ring (circular or elliptical) creep test specimens. Each specimen type has its own unique advantages and disadvantages and it may not be obvious which one is the most appropriate test method to use. This paper gives a brief description of each specimen and associated test type and describes their practical limitations. The suitability of each of the methods for determining “bulk” material properties is described and it is shown that an appropriate test type can be chosen.

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Copyright © 2014 by ASME
Topics: Creep
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References

Parker, J. D., and James, J. D., 1994, “Creep Behaviour of Miniature Disc Specimens of Low Alloy Steel,” ASME, PVP Development in a Progressing Technology, Vol. 279, pp. 167–172.
Hermosilla, U., Hyde, T. H., and Jones, I. A., 2008, “Thermal Analysis of Electron-Beam Physical Vapour Deposited Thermal Barrier Coated Super-Alloy Tensile Specimens,” Proc. Inst. Mech. Eng., Part L, 222, pp. 141–150. [CrossRef]
Hyde, T. H., Sun, W., Becker, A. A., and Williams, J. A., 2004, “Creep Behaviour and Failure Assessment of New and Fully Repaired P91 Pipe Welds at 923 K,” Proc. Inst. Mech. Eng., Part L, 218, pp. 211–222. [CrossRef]
Hyde, T. H., Sun, W., and Becker, A. A., 1996, “Analysis of the Impression Creep Test Method Using a Rectangular Indenter for Determining the Creep Properties in Welds,” Int. J. Mech. Sci., 38, pp. 1089–1102. [CrossRef]
Hyde, T. H., and Sun, W., 2009, “A Novel, High Sensitivity, Small Specimen Creep Test,” J. Strain Anal., 44(3), pp. 171–185. [CrossRef]
Hyde, T. H., and Sun, W., 2010, “Some Considerations on Specimen Types for Small Sample Creep Tests,” Mater. High. Temp., 27(3), pp. 157–165. [CrossRef]
Hyde, T. H., and Sun, W., 2009, “Evaluation of the Conversion Relationship for Impression Creep Testing,” Int. J. Pressure Vessels Piping, 86(11), pp. 757–763. [CrossRef]
Sun, W., and Hyde, T. H., 2010, “Determination of Secondary Creep Properties Using a Small Ring Creep Test Technique,” Metall. J., 63, pp. 185–193.
Li, Y. Z., and Šturm, R., 2008, “Determination of Creep Properties From Small Punch Test,” Proceedings of ASME Pressure Vessels and Piping Division Conference, July 27–31, Chicago, IL.
Hyde, T. H., Miroslav, S., Sun, W. and Hyde, C. J., 2010, “On the Interpretation of Results From Small Punch Creep Test,” J. Strain Anal., 45(3), pp. 141–164. [CrossRef]
Askins, M. C., and Marchant, K. D., 1987, “Estimating the Remanent Life of Boiler Pressure Parts,” EPRI Contract RP2253-1, Part 2, Miniature Specimen Creep Testing in Tension, CEGB Report, TPRD/3099/R86, CEGB, United Kingdom.
Hyde, T. H., Sun, W., and Brett, S. J., 2009, “Some Recommendations on Standardization of Impression Creep Testing,” Proceedings of ECCC Conference on Creep and Fracture in High Temperature Components–Design and Life Assessment, I. A.Shibli and S. R.Holdsworth, eds., Apr. 21–23, DEStech Publications, Dübendorf, Switzerland, pp. 1079–1087.
Hyde, T. H., Sun, W., and Williams, J. A., 2007, “The Requirements for and the Use of Miniature Test Specimens to Provide Mechanical and Creep Properties of Materials—A Review,” Int. Mater. Rev., 52(4), pp. 213–255. [CrossRef]
Sun, W., Hyde, T. H., and Brett, S. J., 2008, “Application of Impression Creep Data in Life Assessment of Power Plan Materials at High Temperatures,” Proc. Inst. Mech. Eng., Part L, 222, pp. 175–182. [CrossRef]
. CEN CWA 15627, 2006, Workshop Agreement: Small Punch Test Method for Metallic Materials (Part A), European Committee for Standardisation.
Li, Y. Z., Šturm, R., Hurst, R., and Blagoeva, D., 2011, “Derivation of Creep Properties From Small Punch Test Small Punch Test (SPT),” International Workshop—June 27/28, University of Nottingham, United Kingdom.
Hyde, T. H., and Sun, W., 2001, “Multi-Step Load Impression Creep Tests for a 1/2CrMoV Steel at 565 °C,” Strain, 37, pp. 99–103. [CrossRef]

Figures

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Fig. 1

Small material samples

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Fig. 2

“Standard” uniaxial creep test specimen (GL ≈ 30–50 mm; dGL ≈ 6–10 mm; L = 100–130 mm)

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Fig. 3

Shapes and dimensions of small creep test specimens: (a) conventional sub-size uniaxial specimen (GL ≈ 5–12 mm; dGL ≈ 1–3 mm); (b) SPT specimen (D ≈ 8 mm; to ≈ 0.5 mm); (c) ICT specimen (w = bi ≈ 10 mm; di ≈ 1 mm; h ≈ 2.5 mm); (d) circular SRT (R ≈ 5 mm, d ≈ 1 mm, and depth bo ≈ 2 mm); and (e) elliptical SRT (a ≈ 15 mm, b ≈ 7.5 mm, d ≈ 1 mm, and depth bo ≈ 2 mm)

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Fig. 4

Schematics diagrams showing the small specimen loading arrangements: (a) uniaxial; (b) SPT; (c) ICT; (d) circular SRT; and (e) elliptical SRT

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Fig. 5

(a) Uniaxial minimum creep strain rate data obtained with standard specimen (Fig. 2) on a P91 steel at 600  °C [3] and (b) uniaxial creep rupture data obtained with standard specimen (Fig. 2) on a P91 steel at 600  °C [3]

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Fig. 6

Minimum creep stain rate data for 316 stainless steel at 600 °C and 2-1/4r1Mo weld metal at 640 °C, obtained from uniaxial and impression creep tests (e.g., Ref. [17])

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Fig. 7

(a) Minimum creep strain rate data for a P91 steel at 650 °C obtained from uniaxial and SRC tests [8] and (b) minimum creep strain rate data for a Nickel base superalloy at 800  °C obtained from uniaxial and SRC tests

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Fig. 8

(a) Converted creep rupture data (using Eq. (3), with Ks = 1) obtained from a SPT on a P91 steel at 650  °C, compared with corresponding uniaxial data [16] and (b) converted creep rupture data (using Eq. (3), with Ks = 1.275) obtained from a SPT on a P91 steel at 650  °C, compared with corresponding uniaxial data [16]

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