Chapter 16. Evaluation of the Stress State in a Buttonhead, Tensile Specimen for Ceramics

  1. John B. Wachtman Jr.
  1. M. G. Jenkins,
  2. M. K. Ferber and
  3. R. L. Martin

Published Online: 26 MAR 2008

DOI: 10.1002/9780470313053.ch16

14th Annual Conference on Composites and Advanced Ceramic Materials, Part 2 of 2: Ceramic Engineering and Science Proceedings, Volume 11, Issue 9/10

14th Annual Conference on Composites and Advanced Ceramic Materials, Part 2 of 2: Ceramic Engineering and Science Proceedings, Volume 11, Issue 9/10

How to Cite

Jenkins, M. G., Ferber, M. K. and Martin, R. L. (1990) Evaluation of the Stress State in a Buttonhead, Tensile Specimen for Ceramics, in 14th Annual Conference on Composites and Advanced Ceramic Materials, Part 2 of 2: Ceramic Engineering and Science Proceedings, Volume 11, Issue 9/10 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470313053.ch16

Author Information

  1. Metals and Ceramics Division, Oak Ridge National Laboratory

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1990

ISBN Information

Print ISBN: 9780470374931

Online ISBN: 9780470313053

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Keywords:

  • hydraulic;
  • methodologies;
  • geometries;
  • ceramics;
  • equilibrium

Summary

An analysis of the stress state in a buttonhead, tensile specimen with two types of gripping systems was conducted using finite element analysis (FEA) methods and empirical tests with strain gauges. The FEA modeling revealed stress concentrations (kt) existing at the buttonhead and at the transition from the gauge section to the shank. However, the stress field within the bulk of the gauge section is uniform and uniaxial. The buttonhead kt varied from 0.35–0.72 of the gauge section stress for tapered collet or straight collet systems, respectively. Empirical tests confirmed these results whereby the tapered collet system, compared to the straight collet system, sustained over twice the average load before failure at the buttonhead. In addition, using hydraulic couplers in the loadtrain, the percent bending at failure ranged from 0.4–4.9 (average = 2.5) and from 1.5–6.3 (average = 3.9) for the tapered and straight collet systems, respectively. A statistically based analysis was made on the effect of bending on the measurement of characteristic strengths and a practical upper limit of 5.0% bending is suggested for tensile strength tests.