Chapter 28. Toughness, Crack Propagation, and Size Effect on Strength of Westerly Granite

  1. William Smothers
  1. Karl R. McKinney,
  2. Carl Cm. Wu and
  3. Roy W. Rice

Published Online: 26 MAR 2008

DOI: 10.1002/9780470320280.ch28

Proceedings of the 9th Annual Conference on Composites and Advanced Ceramic Materials: Ceramic Engineering and Science Proceedings, Volume 6, Issue 7/8

Proceedings of the 9th Annual Conference on Composites and Advanced Ceramic Materials: Ceramic Engineering and Science Proceedings, Volume 6, Issue 7/8

How to Cite

McKinney, K. R., Wu, C. Cm. and Rice, R. W. (1985) Toughness, Crack Propagation, and Size Effect on Strength of Westerly Granite, in Proceedings of the 9th Annual Conference on Composites and Advanced Ceramic Materials: Ceramic Engineering and Science Proceedings, Volume 6, Issue 7/8 (ed W. Smothers), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470320280.ch28

Author Information

  1. Naval Research Lab Washington, DC 20375-5000

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1985

ISBN Information

Print ISBN: 9780470374337

Online ISBN: 9780470320280

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Keywords:

  • toughness;
  • crack propagation;
  • KQ;
  • kobayashi and fourney;
  • ASTM

Summary

A variety of tests is used to characterize the fracture properties of Westerly granite. The fracture toughness, KIC, is found to be ≈1.9 MPa √m using double torsion tests which are also used to show sub-critical crack growth and, therefore, the likelihood of delayed failure. Bend bars of a spectrum of sizes from 25 mm down to 3 mm square show strengths of 233 MPa in one direction and about 20% less in the other two directions for the smallest bars, with little or no such change for 6x6 mm bars. Delayed failure tests using the smaller bars support the directional results. Also, tests of larger bars do not show the strength trend predicted by Weibull statistics, but, instead show almost constant strength. Delayed failure is also found in 3 × 3 mm and 6 × 6 mm bars tested in liquid nitrogen, but at a much reduced rate. Notched bend tests of bars of three different sizes cut in two directions show no toughness orientation effect, but a decrease in apparent toughness, Kq, as shorter critical crack length is used. This result extrapolates well to the data of other researchers.