Chapter 18. Contact-Free Ultrasound: The Final Frontier in Non-Destructive Materials Characterization

  1. Todd Jessen and
  2. Ersan Ustundag
  1. M. C. Bhardwaj,
  2. I. Neeson,
  3. M. E. Langron and
  4. L. Vandervalk

Published Online: 26 MAR 2008

DOI: 10.1002/9780470294628.ch18

24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 21, Issue 3

24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 21, Issue 3

How to Cite

Bhardwaj, M. C., Neeson, I., Langron, M. E. and Vandervalk, L. (2000) Contact-Free Ultrasound: The Final Frontier in Non-Destructive Materials Characterization, in 24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 21, Issue 3 (eds T. Jessen and E. Ustundag), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294628.ch18

Author Information

  1. Second Wave Systems 1020 E. Boal Avenue Boalsburg, PA 16827 USA

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 2000

ISBN Information

Print ISBN: 9780470375686

Online ISBN: 9780470294628

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Keywords:

  • thermal shock property;
  • silicon nitride;
  • thermal stress distribution;
  • tensile stress;
  • ceramic components

Summary

Adhering to the objectives of non-destructive materials characterization, a contact-less—air-coupled—method of ultrasound is highly desirable. However, exorbitant acoustic impedance mismatch between the coupling air and the test media presents a natural impediment to NCU. This impedance mis-match can be as high as seven orders of magnitude for some materials. Therefore, high frequency Non-Contact Ultrasound (NCU) propagation in materials has been regarded as an impossibility. On the other hand, low frequency ultrasound—25kHz to 100kHz—can be propagated through materials in non-contact mode. However, these frequencies are practically useless for the interrogation of most materials where the industry demands high resolution and high detectability. Recent advances in high transduction high frequency piezoelectric transducers (200kHz to 5MHz) and an exceptionally high dynamic range nanosecond accuracy ultrasonic system have advanced the NCU practice to levels that rival conventional contact method. In this paper we provide an introduction to NCU and present examples of green and sintered ceramics and composites analysis. Applications of NCU are considered to be truly significant for cost-effective manufacturing of high reliability materials.