Journal of Materials Science

, Volume 47, Issue 6, pp 2770–2781 | Cite as

A new statistical framework for the determination of safe creep life using the theta projection technique

  • M. Evans


In this article a new estimation framework is put forward for the well-known theta projection technique which enables, for the first time, levels of confidence to be associated with the creep property predictions made using this technique. The predictions made from the resulting model are in the form of distributions, which is a substantial advance on existing life assessment methodologies used in high-temperature applications such as the disks and blades used in aero engines. This additional information should prove invaluable for questions related to the issues of possible life extension. When applied to data on Ti., accurate interpolations and extrapolations could be made of the actual distribution of the minimum creep rate, which in combination with the Monkman–Grant relation, also enabled accurate predictions to be made for the time to failure. For example, when extrapolating to a stress of 480 MPa, the time to failure was predicted to follow a non-normal distribution with a median time of 3450 h and a 95% confidence interval of 3250–3800 h. The single experimental data point available at this stress was consistent with such an extrapolation.


Post Weld Heat Treatment Creep Curve Creep Property Minimum Creep Rate Tertiary Creep 
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  1. 1.
    Larson FR, Miller J (1952) Trans ASME 174(5)Google Scholar
  2. 2.
    Evans RW, Wilshire B (1999) Introduction to creep, Appendix A. The Institute of Materials, BournemouthGoogle Scholar
  3. 3.
    Evans RW, Wilshire B (1984) Creep of metals and alloys. The Institute of Metals, LondonGoogle Scholar
  4. 4.
    Evans RW, Willis MR, Wilshire B, Holdsworth S, Senior B, Fleming A, Spindler M, Williams JA (1993) In: Proceedings of the 5th international conference on creep and fracture of engineering materials and structures, University College Swansea, Swansea, p 633Google Scholar
  5. 5.
    Brown SGR, Evans RW, Wilshire B (1986) Mater Sci Eng 84(1–2):147Google Scholar
  6. 6.
    Evans RW, Hull RJ (1996) J Mater Proc Technol 56(1–4):492CrossRefGoogle Scholar
  7. 7.
    Evans M (2001) J Mater Sci 36:2875. doi: 10.1023/A:1017946218860 CrossRefGoogle Scholar
  8. 8.
    Evans RW (2001) Mater Sci Technol 17(5):487Google Scholar
  9. 9.
    Evans RW (2000) Mater Sci Technol 16(1):6CrossRefGoogle Scholar
  10. 10.
    Evans RW (1989) Mater Sci Technol 5(7):699Google Scholar
  11. 11.
    Penny RK, Marriott DL (1995) Design for creep. Chapman & Hall, LondonCrossRefGoogle Scholar
  12. 12.
    Evans M, Ward AR (2000) Mater Sci Technol 16(10):1149Google Scholar
  13. 13.
    Yokoi S (ed) National Institute for Materials Science, various creep data sheets, TokyoGoogle Scholar
  14. 14.
    ECCC Recommendations. In: Bullough CK, Merckling G (eds) Data exchange and collation, vol 4, HoldsworthGoogle Scholar
  15. 15.
    Goldstein H (2003) Multilevel statistical models, 3rd edition, appendix to chapter 2. Wiley, LondonGoogle Scholar
  16. 16.
    Laird NM, Ware JH (1982) Biometrics 38:963CrossRefGoogle Scholar
  17. 17.
    Lindstrom MJ, Bates DM (1988) J Am Stat Assoc 83:1014CrossRefGoogle Scholar
  18. 18.
    Maddala GS, Li H, Trost RP, Joutz F (1997) J Bus Econ Stat 15:90CrossRefGoogle Scholar
  19. 19.
    Hougaard PP (2000) Analysis of multivariate survival data. Springer-Verlag, New YorkCrossRefGoogle Scholar
  20. 20.
    Lawless JF (1982) Statistical models and methods for lifetime data, Chapter 1. Wiley, New YorkGoogle Scholar
  21. 21.
    Abramowitz M, Stegun IA (eds) Handbook of mathematical functions. Dover, New YorkGoogle Scholar
  22. 22.
    Monkman FC, Grant NJ (1963) In: Mullendore AW, Grant NJ (eds) Deformation and fracture at elevated temperature. MIT Press, BostonGoogle Scholar
  23. 23.
    Bourgeois M, Feaugas X, De Mestral F, Chauveau T, Cla M (1995) In: Proceedings of the 8th world conference on titanium, International Convention Centre, BirminghamGoogle Scholar
  24. 24.
    Bourgeois MM, Feaugas X, De Mestral F, Chauveau T, Cla M (1996) Rev Metall Cshiers Inf Tech 93(12):1521Google Scholar
  25. 25.
    Bartlett MS, Kendall DG (1946) J R Stat SocGoogle Scholar
  26. 26.
    Prentice SRL (1975) Biometrika 61:539CrossRefGoogle Scholar
  27. 27.
    Greene WH (2008) Econometric analysis, 6th edn. New Jersey, Prentice HallGoogle Scholar
  28. 28.
    Box GEP, Muller ME (1958) Annal Math Stat 29:610CrossRefGoogle Scholar
  29. 29.
    Microsoft Excel: Microsoft Office (2007)Google Scholar

Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  1. 1.Materials Research Centre, College of EngineeringSwansea UniversitySwanseaUK

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