Chapter 8. A Strain-Based Methodology for High Temperature Lifetime Prediction

  1. Don Bray
  1. S. M. Wiederhorn,
  2. W. E. Luecke and
  3. R. F. Krause Jr.

Published Online: 23 MAR 2010

DOI: 10.1002/9780470294499.ch8

22nd Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: B: Ceramic Engineering and Science Proceedings, Volume 19, Issue 4

22nd Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: B: Ceramic Engineering and Science Proceedings, Volume 19, Issue 4

How to Cite

Wiederhorn, S. M., Luecke, W. E. and Krause, R. F. (1998) A Strain-Based Methodology for High Temperature Lifetime Prediction, in 22nd Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: B: Ceramic Engineering and Science Proceedings, Volume 19, Issue 4 (ed D. Bray), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294499.ch8

Author Information

  1. National Institute of Standards and Technology Gaithersburg, MD 20899

Publication History

  1. Published Online: 23 MAR 2010
  2. Published Print: 1 JAN 1998

ISBN Information

Print ISBN: 9780470375594

Online ISBN: 9780470294499

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Keywords:

  • molybdenum;
  • thermal conditioning;
  • coupling;
  • contamination;
  • mechanism

Summary

In structural materials, lifetime is often strain-determined. Once a part exceeds its allowable strain, its functional integrity is lost. Although most ceramics are designed to a brittle failure criterion, silicon nitride at the temperatures expected in gas turbines is an exception to this generality. In the temperature range and at the stresses expected in gas turbines, silicon nitride can easily exhibit strains to failure that exceed 1%. Because an allowable strain of only 0.5 % is used for gas turbine design, the necessity of a strain-determined design methodology must be considered. In this paper the consequences of creep on design are considered for an allowable strain of 0.5 % and a reliability of one failure in 10,000. For a given stress and failure time, we show that reductions in operating temperature by as much as 40 °C are needed when strain rather than creep rupture is considered as the failure criterion. An additional 25 °C reduction is needed to assure the reliability level to one part in 10,000.