High Frequency Non-Contact Ultrasonic Analysis: A Practical Reality

摘要

Air-coupled transducers in less than MHz range have been known for some time. However, non-contact transducers up to 5MHz with sensitivity only 30dB lower than conventional contact transducers described here, open new possibilities for industrial and bio-medical applications. In comparison the NCU mode rivals the contact liquid-coupling mode of ultrasound. This development in conjunction with the NCA 1000 now allows execution of routine NDE tasks plus analysis equivalent to materials characterization methods based upon other wave phenomena. By documentary evidence we have shown the transducer characteristics, proof of very high sensitivity, and a few applications of interest to industry and health care. The NCA 1000 is a sophisticated laboratory tool that can be easily adapted to on-line applications. It should be of interest to note that this system and transducers have been successfully integrated into factories and laboratories worldwide. For further information about our work into non-contact ultrasound, please see the following: 1. Bhardwaj, M.C., "Innovation in Non-Contact Ultrasonic Analysis: Applications for Hidden Objects Detection," Mat. Res. Innovat. (1997) 1:188-196. 2. Jones, J.P, Lee, D., Bhardwaj, M., Vanderkam, V., and Achauer, B., "Non-Contact Ultrasonic Imaging for the Evaluation of Burn-Depth and for Other Biomedical Applications," Acoust. Imaging, V. 23 (1997). 3. Bhardwaj, M.C., "Non-Contact Ultrasonic Characterization of Ceramics and Composites," Proceedings Am.Cer.Soc., V 89 (1998). 4. T. Carneim, D.J. Green & M.C. Bhardwaj, "Non-Contact Ultrasonic Characterization of Green Bodies," Cer. Bull., April 1999. 5. Bhardwaj, M.C., "High Transduction Piezoelectric Transducers and Introduction of Non-Contact Analysis," a chapter submitted for the Encyclopedia of Smart Materials, ed. J.A. Harvey, Wiley, New York (2000).