It is frequently necessary to inspect structures operating at temperatures above 3000C, or in high radiation environments. In these cases it becomes more difficult to use conventional ultrasonic transducers. A radical alternative is to use an acoustic waveguide made from a radiation and temperature resistant material (e.g. stainless steel or ceramic) to couple the energy into the test structure from a transducer and instrumentation located in an area where they can be operated easily; the end of the waveguide is attached directly to the critical structure at the point of interest. Effectively this approach uses an 'acoustic cable' to interrogate the test area instead of the conventional approach which uses an electrical cable, so that all the electrical parts of the system are outside the harsh environment. This makes both continuous health monitoring and periodic inspection much easier. We have successfully developed this concept and have formed a spin-out company, Permasense Ltd, to commercialise it (www.permasense.com) . The sensors will monitor thickness at temperatures up to 6000C and transmit the measured thickness via a wireless link. Current work in the group is further developing the technology to diagnose pitting, rather than uniform wall loss, and to monitor cracking. You can view a presentation here.

Sponsors

BP and EPSRC

References

F. B. Cegla. Energy concentration at the centre of large aspect ratio rectangular waveguides at high frequencies. Journal of the Acoustical Society of America, Vol. 123, No. 6, pages 4218-4226, Jun. 2008

 F. B. Cegla, J.O. Davis, J. Allin.  High-Temperature (> 500 degrees C) Wall Thickness Monitoring Using Dry-Coupled Ultrasonic Waveguide Transducers, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol. 58, No. 1, pages 156-167, Jan. 2011

F.B. Cegla, J.O. Davies, “Ultrasonic Crack Monitoring at High Temperatures Using SH Waves (> 500 degrees C) “ Review of Progress in Quantitative NDE, eds. D.O. Thompson and D.E. Chimenti, American Institute of Physics, New York, vol. 29, pp. 980-987 , 2010.

F. Cegla, J. Allin, Wireless Ultrasonic Thickness Monitoring at Elevated Temperatures, Materials Evaluation,  Volume: 69 Issue: 5 Pages: A26-A31  MAY 2011 

F.B. Cegla, A.J.C. Jarvis, J.O. Davies. High temperature ultrasonic crack monitoring using SH waves, NDT & E International, Volume 44, Issue 8, December 2011, Pages 669-679