Project Leader: C.M. Fortunko
D.A. Hurley, M.A. Hamstad, R.L. Santoyo, J.D. McColskey,
M.C. Renken, E.S. Boltz

MSEL Program Nondestructive Evaluation	MRD Focus Technology Ultrasonic Characterization
Strategic Thrust Measurement Base and Standards	Character of Research Measurement Research

Technical Description

High-resolution ultrasonic techniques and instrumentation are being developed to facilitate characterization of microstructure and failure mechanisms of advanced materials. In particular, advances are being made in high-fidelity acoustic emission and nonlinear ultrasonics. The acoustic-emission work is enabled by the availability of new wideband transducers, electronics, and sound-propagation models, which should facilitate source location and damage characterization. In addition, the new techniques will improve discrimination of acoustic emission events from extraneous-noise signals. The work in the area of nonlinear ultrasonics is also motivated by a need for better microstructure-characterization methods. Therefore, emphasis is placed on quantifying the relationships between nonlinear material responses and microstructural features. Both theoretical and experimental tools are being developed for this purpose.

Technical Objectives

1. Develop wideband, high-fidelity acoustic-emission methods, including necessary measurement methods and instrumentation, for source location and damage characterization.

2. Develop an understanding of acoustic-emission phenomena in order to facilitate discrimination of acoustic-emission events from extraneous noise.

3. Develop and evaluate theoretical models and experimental apparatus for nonlinear ultrasonic studies of material microstructure.

4. Establish and validate quantitative relationships between nonlinear ultrasonic phenomena and microstructure. Apply such relationships to practical material systems, including advanced coatings.

FY95 Accomplishments

Compared the performance of wideband (NIST-developed) acoustic emission sensors with conventional, resonant sensors. Showed that the use of wideband sensors can improve discrimination between extraneous noise and acoustic emissions.

Developed wideband acoustic emission sensors for fiber-reinforced composite materials. Showed that such transducers can be used to locate acoustic emission sources in such materials as well as monitor the state of damage.

Established a CRADA with Dunegan Engineering Consultants, Inc. The purpose of the agreement is to jointly develop an improved, commercial sensor for wideband acoustic emission applications.

Established an informal working group in the area of nonlinear ultrasonics. The group now includes Johns Hopkins University, Ritec, Inc., Southwest Research Institute, NIST, NASA, and the (German) Institute for Nondestructive Testing.

Took possession of and evaluated a new, first-of-a-kind ultrasonic instrumentation system for non-linear ultrasonic studies of materials. The instrument was developed under a CRADA agreement with Ritec, Inc. The results of the NIST tests will be incorporated in a second prototype of the instrument and in production versions, which will be sold commercially.

FY95 Outputs

1. E.S. Boltz, C.M. Fortunko, M.A. Hamstad, and M.C. Renken, "Absolute Sensitivity Limits of Air, Light and Direct-Coupled Wideband Acoustic Emission Transducers," in Proc. 1994 Review of Progress in Quantitative NDE, edited by D.O. Thompson and D.E. Chimenti (Plenum Press, New York, 1995), pp. 967-974.

2. C.M. Fortunko, R.E. Schramm, C.M. Teller, G.M. Light, J.D. McColskey, W.P. Dube, M.C. Renken, "Gas-Coupled, Pulse-Echo Ultrasonic Crack Detection and Thickness Gaging," in Proc. 1994 Review of Progress in Quantitative NDE, edited by D.O. Thompson and D.E. Chimenti (Plenum Press, New York, 1995), pp. 951-958.

3. M.A. Hamstad and C.M. Fortunko, "Development of Practical Wideband High-Fidelity Acoustic Emission Sensors," in Proc. of SPIE Conf. on "Nondestructive Evaluation of Aging Infrastructure 1995," June 6-8, 1995, edited by S. Chase, Proc. SPIE, Vol. 2456, (1995), pp. 281-288.

4. E.S. Boltz and C.M. Fortunko, "Determination of the Absolute Sensitivity Limit of a Piezoelectric Displacement Transducer," in Proc. 1995 Review of Progress in Quant. NDE, D.O. Thompson and D.E. Chimenti eds. (Plenum, New York, 1995) in press.

5. M.C. Renken and C.M. Fortunko, "Impact of Quantization Noise on the Quality of Ultrasonic Signal Deconvolution," in Proc. 1995 Rev. of Prog. in Quant. NDE, D.O. Thompson and D.E. Chimenti eds. (Plenum, New York, 1995) in press.

6. C.M. Fortunko and E.S. Boltz, "Comparison of Absolute Sensitivity Limits of Various Ultrasonic and Vibration Transducers," in Proc. of the Seventh International Conf. on Nondestructive Characterization of Materials, June 19-24, Prague (Plenum, New York, 1996) in press.

7. E.S. Boltz and C.M. Fortunko, "Absolute Sensitivity of Various Ultrasonic Transducers," in Proc. 1995 Ultrasonics Symp. B.R. McAvoy ed. (IEEE, New York, 1995), in press.