Advertisement

The Use of CTOD Methods in Fitness for Purpose Analysis

  • T. L. Anderson
  • R. H. Leggatt
  • S. J. Garwood

Summary

A three tier fracture assessment procedure is proposed which allows flaws to be assessed at various levels of complexity, depending on the application. All three levels utilise crack tip opening displacement (CTOD) as the fracture toughness input. The CTOD design curve, with minor modifications, occupies the first (simplest) level. Several restrictions to the application of the CTOD design curve are recommended. The second level utilises a strip yield model, which is reasonably accurate below net section yield. Level 3, the most complex and accurate method, utilises a reference stress approach which allows fracture assessments to be performed on work hardening materials above net section yield. The proposed three tier procedure also allows for some flexibility in the way stress gradients are treated. The proposed options for treating stress gradients range from simple and conservative to complex and accurate. Some guidelines for choosing the appropriate assessment level are given.

Keywords

Linear Elastic Fracture Mechanic Primary Stress Secondary Stress Design Curve Reference Stress 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    PD. 6493. “Guidance on some methods for the derivation of acceptance levels for defects in fusion welded joints”. British Standards Institution, March 1980.Google Scholar
  2. 2.
    HARRISON, R.P., LOOSEMOORE, K., MILNE, I., and DOWLING, A.R. “Assessment of the integrity of structures containing defects”. CEGB Report R/H/R6-Rev. 2, 1980.Google Scholar
  3. 3.
    TURNER, C.E. “The J-estimation curve, R-curve, and tearing resistance concepts leading to a proposal for a J-based design curve against fracture”. proc. conf. “Fitness for purpose validation of welded constructions.” The Welding Institute, Paper 17, 1982.Google Scholar
  4. 4.
    BURDEKIN, F.M. “Final report on questionare on the use of fracture mechanics methods for the assessment of the significance of weld defects”. IIW Document X-1076–84, 1984.Google Scholar
  5. 5.
    MILNE, I., DOWLING, A.R., AINSWORTH, R.A., and STEWART, A.T. “Assessment of the integrity of structures containing defects - addendum for structures made with a high capacity for work hardening”. CEGB Report R/H/R6-Rev.2, Addendum 1, December 1984.Google Scholar
  6. 6.
    DAWES, M.G. “The COD design curve”. 2nd Advanced Seminar on Fracture Mechanics, Ispra, Italy, April 1979. (Published in ‘Advances in Elastro-Plastic Fracture Mechanics’, Edit. L.H. Larsson, Applied Science Publishers, London, 1979 ).Google Scholar
  7. 7.
    KAMATH, M.S. “The COD design curve: an assessment of validity using wide plate tests.” Welding Institute Report 71/1978/E, September 1979.Google Scholar
  8. 8.
    DAWES, M.G. “The CTOD design curve approach: limitations and finite size”. Welding Institute Report 278 /1985, June 1985.Google Scholar
  9. 9.
    WILLOUGHBY, A.A. “A survey of plastic collapse solutions used in the failure assessment of part wall defects”. Welding Institute Report 191 /1982, September 1982.Google Scholar
  10. 10.
    KAMATH, M.S. “The crack tip opening displacement (CTOD) design curve: some proposals for incorporating stress gradient effects”. proc. conf. “Fitness for purpose validation of welded constructions”. The Welding Institute, Paper 23, 1982.Google Scholar
  11. 11.
    HARRISON, J.D. “Fracture mechanics developments related to weld defect acceptance methods given in British Standard PD 6493”. Presented at “Fracture 84, 2nd National Conference on Fracture”. Johannesburg, South Africa, November 1984.Google Scholar
  12. 12.
    ANDERSON, T.L. “Elastic-plastic fracture assessments based on CTOD”. Welding Institute Report 276 /1985, June 1985.Google Scholar
  13. 13.
    DUGDALE, D.S. “Yielding in steel sheets containing slits”. J. Mech. Phys. Solids, 8, 1960. p. 100.CrossRefADSGoogle Scholar
  14. 14.
    BURDEKIN, F.M. and STONE, D.E.W. “The crack opening displacement approach to fracture mechanics in yielding materials”. Journal of Strain Analysis, 1 (2), 1966, p. 144.CrossRefGoogle Scholar
  15. 15.
    BILBY, B.A., COTTRELL, A.H. and SWINDEN, K.H. “The spread of plastic yield from a notch”. Proc. Royal Society, A 272, 1963, p. 304.CrossRefGoogle Scholar
  16. 16.
    HEALD, P.T., SPINK, G.M. and WORTHINGTON, P.J. “Post yield fracture mechanics”. Mat. Sci. Eng., 10, 1972, p. 129.CrossRefGoogle Scholar
  17. 17.
    GARWOOD, S.J. “A crack tip opening displacement (CTOD) method for the analysis of ductile materials”. Presented at the Eighteenth National Symposium on Fracture Mechanics, 25–27 June 1985, Boulder, Colorado, U.S.A.Google Scholar
  18. 18.
    KUMAR, V., GERMAN, M.D. and SHIN, C.F. “An engineering approach for elastic plastic fracture analysis”. EPRI Report NP 1931, July 1981.Google Scholar
  19. 19.
    HUTCHINSON, J.W. “Singular behaviour at the end of a tensile crack in a hardening material”. J. Mech. Phys. Solids, 16, 1968, p. 13.CrossRefMATHADSGoogle Scholar
  20. 20.
    RICE, J.R. and ROSENGREN, G.F. “Plane strain deformation near a crack tip in a power-law hardening material”. J. Mech. Phys. Sol., 1–12.Google Scholar
  21. 21.
    AINSWORTH, R.A. “The assessment of defects in structures of strain hardening material”. Eng. Frac. Mech., 19, 1984, p. 633.CrossRefGoogle Scholar
  22. 22.
    ANDERSON, T.L., GORDON, J.R. and GARWOOD, S.J. “On the application of R-curves and maximum load toughness to structures.” Submitted for presentation at the Nineteenth Symposium on Fracture Mechanics, 30 June - 2 July 1986 San Antonio, Texas, U.S.A..Google Scholar

Copyright information

© Springer-Verlag Berlin, Heidelberg 1986

Authors and Affiliations

  • T. L. Anderson
    • 1
  • R. H. Leggatt
    • 1
  • S. J. Garwood
    • 1
  1. 1.The Welding InstituteAbington Hall AbingtonCambridgeEngland

Personalised recommendations