Journal of Materials Science

, Volume 43, Issue 6, pp 1825–1835 | Cite as

The small punch creep test: some results from a numerical model

  • M. EvansEmail author
  • D. Wang


Obtaining accurate estimates of remanent creep life is of great importance to the power generating industry. The small punch creep test promises to be a useful way forward in this respect. However, a major concern with the test revolves around the ability to convert small punch test data into the required uniaxial equivalents. Experimental results within the literature have given contradictory results partly due to the large experimental scatter inherent within the test and so this article reports some results from a recently developed stochastic finite element model of the small creep punch test that provides guidance on this matter. The uniqueness of the model is based on its realistic creep deformations laws, including strain hardening, thermal softening and damage accumulation that enables it to produce life predictions for virgin material as well as for material with pre existing damage. It is shown that the model produces excellent life predictions for virgin 0.5Cr–0.5Mo–0.25V steel and for damaged 1.25Cr–1Mo steel over a wide range of test conditions. The model also predicts that the dependency of the time to failure on minimum displacement rates is such that small punch test data can be converted into uniaxial data using relatively simple analytical expressions.


Failure Time Minimum Creep Rate Virgin Material Disc Thickness Versus Steel 


\(\dot {\xi}_{ij}\)

Strain rate tensor


Total creep strain at time t (%/100)


Elongation at failure (%/100)


Minimum creep rate (s−1) from uniaxial tests


Minimum displacement rate (mm(s−1)) from small punch test


Theta parameter used to describe a creep curve (j = 1, 4)


Natural log of θj


Mean value for Θj


Randomly generated value for Θj


Randomly generated value for θj


Local Von Mises flow stress


Cauchy stress tensor


Deviatoric stress


Mean stress


Variance of θj


Mean variance of Θj


Normalised stress


Stress (MPa)

aj,0, bj,0, cj,0, dj,0

Parameters of the theta interpolation/extrapolation function in the deterministic model

aj,k, bj,k, cj,k, dj,k

Parameters of the theta interpolation/extrapolation function for the kth run of the stochastic model

a, b, c, d

Parameters of the failure strain interpolation/extrapolation function in the deterministic model


Punch head displacement (mm)

mk, fk

Parameters of the critical damage interpolation/extrapolation function for the kth run of the punch test model

r, z

Disc point coordinates


Temperature (K)


Time at failure


A randomly drawn number between 0 and 1


A standard normal variate


Velocity field




Continuum damage at failure (dimensionless)


Punch hole diameter (mm)


Disc diameter (mm)


Disc thickness (mm)


Punch head radius (mm)


Friction coefficient (0 ≤ x5 ≤ 1)


Preexisting damage (dimensionless)


Load (N)


  1. 1.
    Manahan MP, Argon AS, Harling OK (1981) J Nucl Mater 103–104:1545. North-Holland Publishing Company Google Scholar
  2. 2.
    Mao X, Takahashi H (1987) J Nucl Mater 150:42. North-HollandCrossRefGoogle Scholar
  3. 3.
    Takahashi H, Shoji T, Mao X, Hamaguchi Y, Misawa T, Saito M, Oku T, Kodaira T, Fukaya K, Nishi H, Suzuki M (1988) Recommended practice for small punch (SP) testing of matallic materials. JAERI-M 88-172, SeptGoogle Scholar
  4. 4.
    Foulds JR, Jewitt CW, Bisbee LH, Whicker GA, Viswanathan R (1992) Miniature sample removal and small punch testing for in-service component FATT. Proceedings, Robert I. Jaffee memorial symposium on clean materials technology ASM, pp 101–109Google Scholar
  5. 5.
    Parker JD, Stratford GC, Shaw N, Spink G, Tate E (1995) Deformation and fracture processes in miniature disc tests of CrMoV rotor steel. Proceedings, third international Charles Parsons turbine conference, vol 2. Institute of Materials, pp 418–428Google Scholar
  6. 6.
    Bicego V, Lucon E, Crudeli R (1995) Integrated technologies for life assessment of primary power plant components. In: Bicego, Nitta, Viswanathan (eds) Proceedings of int. symp. on materials ageing and component life extension, vol I. EMAS, pp 295–305Google Scholar
  7. 7.
    Bulloch JH, Fairman A (1995) Some considerations regarding the small punch testing of important engineering components. In: Hietanen, Auerkari (eds) Proceedings of int. conf. Baltica III, Helsinki, Stockholm, 6–8 June 1995, pp 179–193Google Scholar
  8. 8.
    CEN Workshop Business Plan (2004) Small punch test method for metallic materials. CEN, Brussels, Belgium, Sept 2004Google Scholar
  9. 9.
    Bicego V, Rantala H, Klaput J, Stratford GC, Persio F, Hurst RC (2004) The small punch test method: results from a European creep testing round robin. Proceedings, EPRI conference on life assessment, Hilton Head IslandGoogle Scholar
  10. 10.
    CEN Workshop Agreement (2006) CWA 15627:2006 E, Small punch test method for metallic materials. CEN, Brussels, Belgium, Dec 2006Google Scholar
  11. 11.
    Evans RW, Evans M (2006) J Mater Sci Technol 22(10):1155CrossRefGoogle Scholar
  12. 12.
    Evans M, Wang D (2007) Mater Sci Technol 23:883CrossRefGoogle Scholar
  13. 13.
    Evans RW (2000) Proc R Soc Lond A 456:835CrossRefGoogle Scholar
  14. 14.
    Hankin GL, Toloczko MB, Johnson KI, Khaleel MA, Hamilton ML, Garner FA, Davies RW, Faulkner RG. An investigation into the origin and nature of the slope and the x-axis intercept of the shear punch-tensile yield strength correlation using finite element analysis. In: Hamilton ML et al (eds) Effect of Irradiation on material, 19th international symposium. ASTM 1366, p 1018Google Scholar
  15. 15.
    Evans M, Wang D (2007) J Strain Anal Eng Des 5:389CrossRefGoogle Scholar
  16. 16.
    Stratford GC, Di Persio F, Klaput J (2005) Miniaturised creep testing using the small punch test technique. In: 11th international conference on fracture, Turin, Mar, p 4175Google Scholar
  17. 17.
    Aide Memoire (2006) Miniaturised testing: micro structural evaluation and residual lifetimes. In: The special interest group meeting. National Physical Laboratory, Teddington, 14 Feb 2006Google Scholar
  18. 18.
    Evans RW, Beden I, Wilshire B (1984) Creep life prediction for 0.5Cr 0.5 Mo 0.25 V ferretic steel. In: Wilshire B, Owen DRJ (eds) 2nd international conference on creep and fracture of engineering materials and structures. Pineridge Press, Swansea, p 1277Google Scholar
  19. 19.
    Stratford GC (1994) Type IV cracking in 1 1/4Cr-0.5Mo low alloy steel welds. Ph.D. thesis, University of Wales, SwanseaGoogle Scholar
  20. 20.
    Evans RW, Wilshire B (1996) Constitutive laws for high temperature creep and fracture. In: Krausz AS, Krausz K (eds) Unified laws of plastic deformation. Academic Press, London, pp 107–152CrossRefGoogle Scholar
  21. 21.
    Evans RW, Wilshire B (1993) An introduction to creep, 2nd edn. Institute of Materials, LondonGoogle Scholar
  22. 22.
    Evans RW (1989) Mater Sci Technol 5:699CrossRefGoogle Scholar
  23. 23.
    Evans M, Wang D (2007) Mater Sci Technol 23(8):883CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  1. 1.Materials Research Centre, School of EngineeringSwansea UniversitySwanseaUK
  2. 2.Interdisciplinary Research CentreSwansea UniversitySwanseaUK

Personalised recommendations