Project Title:

Ultrasonic Correlator for Nondestructive Characterization of Materials

04.10-0332
Ultrasonic Correlator for Nondestructive Characterization of Materials
Industrial Quality Inc.
P.O. Box 2397
Gaithersburg
MD
20879-0397
Berger
Harold
NAS1-18258
Amount:   
LaRC
NAS1-17937

Abstract:

   A new cross-correlator has been developed and shown to be useful formaterials characterization.  A simplified cross-correlator technique, originally
developed for work in the kilohertz frequency range, is the primary element in the
new ultrasonic cross-correlator.  The cross-correlator output provides the same information
as the impulse response of a material.  Therefore, the cross-correlator is an attractive
approach for ultrasonic characterization of materials.  In the Phase I program the
range of the cross-correlator has been extended to meghertz frequencies, thereby
making the instrument useful for ultrasonic measure-
ments.  A test made with the new system showed significant differences in frequency
versus time reponse for fatigued and fatigued aluminum samples.  In addition, the
processing of the cross-correlator data has been adapted to an IBM personal computer
making the instrument more generally useful, and leading directly to a Phase II program.
 In the new program the cross-correlator performance will be improved by electronic
changes such as an improved white noise generator, by compatible broadband transducers
and by software modifications leading to display of both frequency and phase.  Further
work to understand the theoretical limits of cross correlation versus conventional
ultrasonic characterization problems will lead to the identifi-
cation of potential applications.  A demonstration will be made of a prototype cross-correlator
instrument to be designed and fabricated as part of the Phase II program.