Advertisement

Metallurgical Transactions A

, Volume 18, Issue 11, pp 1861–1875 | Cite as

Brittle fracture: Weakest link or process zone control?

  • W. W. Gerberich
  • S. -H. Chen
  • C. -S. Lee
  • T. Livne
Symposium on The Stochastic Aspects of Fracture

Abstract

Does brittle fracture instability start from a single event such as a cracked carbide or sulfide or does it start from a series of discontinuous cleavage events, which coalesce together? In fact, either of these may occur depending on the test temperature (low or high), the amount of stored elastic energy at a crack tip (blunt or sharp), and the microstructure of brittle second phases (coarse or fine). The present study was to sort out which of these processes occurs in a coarse-grained high strength, low alloy (HSLA) steel tested at—80 °C (193 K). Statistical distributions of grains and fracture origins were identified in this 108 µm grain size steel. This was accomplished with compact tension specimens equipped with plezoceramic transducers to evaluate microcleavage onset. Termination of the test at various stress intensity levels, KI, followed by fatigue cracking at ΔK << K,I, allowed isolation of multiple cleavage origins. Both the amount of cleavage fracture and a preliminary estimate of fracture toughness could be interpreted in terms of process zone concepts. These rely on a local cleavage fracture stress controlled by microgeometry and a quasi-static equilibrium governed by the process zone size and strength. The conclusion for the steel in the present study is that a discontinuous process zone approach is most descriptive of the stochastic events leading up to brittle fracture.

Keywords

Metallurgical Transaction Acoustic Emission Plastic Zone Crack Front Process Zone 
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.
    T. Lin, A. G. Evans, and R. O. Ritchie:Acta Metall., 1986, vol. 34, no. 11, pp. 2205–16.CrossRefGoogle Scholar
  2. 2.
    J. Dvorak: inFracture 1969, P. L. Pratt, E. H. Andrews, R. L. Bell, N. E. Frost, R. W. Nichols, and E. Smith, eds., Chapman and Hall, London, 1969, pp. 338–49.Google Scholar
  3. 3.
    R. G. Hoagland, A. R. Rosenfield, and G. T. Hahn:Metall. Trans., 1972, vol. 3, pp. 123–36.Google Scholar
  4. 4.
    W. W. Gerberich and N. Moody: inFatigue Mechanisms, J. Fong, ed., ASTM, Philadelphia, PA, 1979, pp. 292–341.Google Scholar
  5. 5.
    W. W. Gerberich:Fracture and Interactions of Microstructure, Mechanism and Mechanics, J. M. Wells and J. D. Landes, eds., TMS-AIME, Warrendale, PA, 1985, pp. 49–74.Google Scholar
  6. 6.
    K. A. Esaklul, W. W. Gerberich, and J. P. Lucas: inInt. Conf. on Technology and Applications of HSLA Steel, ASM Metals Congress Paper 8306-020, ASM, Metals Park, OH, 1983.Google Scholar
  7. 7.
    ASTM Standard E399-81, Annual Book of ASTM Standards, Part 10, 1981.Google Scholar
  8. 8.
    W.W. Gerberich and E. Kurman:Scripta Metall., 1985, vol. 19, pp. 295–98.CrossRefGoogle Scholar
  9. 9.
    C. S. Lee, T. Livne, and W. W. Gerberich:Scripta Metall., 1986, vol. 20, pp. 1137–40.CrossRefGoogle Scholar
  10. 10.
    H. N.G. Wadley, C. B. Scruby, and J. H. Speake:Intern. Metals Revs., 1980, no. 2, pp. 41–64.Google Scholar
  11. 11.
    J. D. Desai and W. W. Gerberich:Engng. Fract. Mech., 1975, vol. 7, pp. 153–65.CrossRefGoogle Scholar
  12. 12.
    W. W. Gerberich and K. Jatavallabhula: inNondestructive Evaluation: Microstructural Characterization and Reliability Strategies, O. Buck and S.M. Wolf, eds., TMS-AIME, Warrendale, PA, 1981, pp. 319–48.Google Scholar
  13. 13.
    M. Kaczorowski and W. W. Gerberich:Scripta Metall., 1986, vol. 20, pp. 1597–1600.CrossRefGoogle Scholar
  14. 14.
    J. Huit and F. McClintock:9th Intern. Congress Appl. Mech., Brussels, 1956, vol. 8, pp. 51–58.Google Scholar
  15. 15.
    W. W. Gerberich and N. Moody: inFracture 1977, D. M. R. Taplin, ed., ICF4, Waterloo, ON, Canada, 1977, vol. 3, pp. 829–37.Google Scholar
  16. 16.
    W. W. Gerberich and A. G. Wright: inProc. 2nd Int. Conf. on Mate rials Degradation, Virginia Tech. Printing, Blacksburg, VA, 1981, pp. 183–206.Google Scholar
  17. 17.
    G. T. Hahn and A. R. Rosenfield:Trans. ASM, 1966, vol. 59, p. 909.Google Scholar
  18. 18.
    W.W. Gerberich and Y.T. Chen:Metall. Trans. A, 1975, vol. 6A, pp. 271–78.Google Scholar
  19. 19.
    R. O. Ritchie: Metal Science, Aug./Sept. 1977, pp. 368–81.Google Scholar
  20. 20.
    a.W. W. Gerberich: “Metallurgical Aspects of Crack-Tip Failure Processes,” ASTM Special Tech. Publ., 1986, in press.Google Scholar
  21. 20.
    b.W. W. Gerberich: “Metallurgical Aspects of Crack-Tip Failure Processes,” ASTM Special Tech. Publ. 945, R.P. Reed and D. T. Read, eds., Philadelphia, PA, 1987, pp. 5–18.Google Scholar
  22. 21.
    D.S. Dugdale:J. Mech. Phys. Solids, 1960, vol. 8, pp. 100–08.CrossRefGoogle Scholar
  23. 22.
    G.I. Barenblatt:in Adv. in Applied Mech., H.L. Dryden and T. von Karman, eds., Academic Press, New York, NY, 1962, vol. 7.Google Scholar

Copyright information

© The Metallurgical of Society of AIME 1987

Authors and Affiliations

  • W. W. Gerberich
    • 1
  • S. -H. Chen
    • 1
  • C. -S. Lee
    • 2
  • T. Livne
    • 3
  1. 1.Department of Chemical Engineering and Materials ScienceUniversity of MinnesotaMinneapolis
  2. 2.Department of Metallurgy and Materials SciencePohang Institute of Science and TechnologyKorea
  3. 3.RAFAEL, Ministry of DefenceHaifaIsrael

Personalised recommendations