Heat shield blocks for a manned space capsule are made to withstand the harsh environments of reentry. The materials that best serve this purpose tend to be very difficult to interrogate using nondestructive testing techniques. As NASA was in the process of building the Orion space capsule, the team was able to inspect a number of discontinuities in the heat shield but was faced with great difficulty in inspecting their bond quality to the composite substrate. While radiographic computed tomography and terahertz were successful in detecting three-dimensional defects such as voids and porosity, they were unable to detect two-dimensional defects, such as kissing unbonds. Consequently, a customized ultrasonic technique was developed by carefully selecting every aspect of the inspection, including couplant and transducer. Several signal processing techniques were then performed to counteract the effects of inhomogeneity and irregular scatter in the acoustic signal. The technique takes into consideration the shape of the raw A-scan, phase of the returned echo, and confidence in the received signal. Additionally, the technique may perform synthetic aperture focusing to enhance the quality of the scans and provide for a relatively reliable technique for detecting kissing unbonds and other discontinuities in the heat shield material.
Alvarez-Arenas, T.E., 2004, “Acoustic Impedance Matching of Piezoelectric Transducers to the Air,” IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 51, No. 5, pp. 624–633.
Bhatia, A. B., and R.A. Moore, 1959, “Scattering of High-Frequency Sound Waves in Polycrystalline Materials,” Journal of the Acoustical Society of America, Vol. 31, No. 8, pp. 1140–1141.
Case, J.T., and S. Kenderian, 2019a, “Orion Heat Shield Bond Quality Inspection: Complete Inspection System,” Materials Evaluation, Vol. 77, No. 1, pp. 102–110.
Case, J.T., and S. Kenderian, S., 2019b, “Orion Heat Shield Bond Quality Inspection: Engineering a Technique,” Materials Evaluation, Vol. 77, No. 1, pp. 94–101.
Case, J.T., M.T. Ghasr, and R. Zoughi, 2011, “Optimum Two-Dimensional Uniform Spatial Sampling for Microwave SAR-Based NDE Imaging Systems,” IEEE Transactions on Instrumentation and Measurement, Vol. 60, No. 12, pp. 3806–3815.
Cawley, P., T. Pialucha, and M. Lowe, 1993, “A Comparison of Different Methods for the Detection of a Weak Adhesive/Adherend Interface in Bonded Joints,” Review of Progress in Quantitative Nondestructive Evaluation, Vol. 12A, eds. D.O. Thompson and D.E. Chimenti, Springer, Boston, Massachusetts, pp. 1531–1538.
Drewry, M. A., R.A. Smith, A.P. Phang, D. Yan, P. Wilcox, and D.P. Roach, 2009, “Ultrasonic Techniques for Detection of Weak Adhesion,” Materials Evaluation, Vol. 67, No. 9, pp. 1048–1058.
Gabor, D., 1946, “Theory of Communication. Part 1: The Analysis of Information,” Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering, Vol. 93, No. 26, pp. 429–441.
Gammell, P., 1981, “Improved Ultrasonic Detection Using the Analytic Signal Magnitude,” Ultrasonics, Vol. 19, No. 2, pp. 73–76.
Hurley, N., and S. Rickard, 2009, “Comparing Measures of Sparsity,” IEEE Transactions on Information Theory, Vol. 55, No. 10, pp. 4723–4741.
Jeong, H., and D.K. Hsu, 1995, “Experimental Analysis of Porosity-Induced Ultrasonic Attenuation and Velocity Change in Carbon Composites,” Ultrasonics, Vol. 33, No. 3, pp. 195–203.
Kharkovsky, S., J.T. Case, M.A. Abou-Khousa, R. Zoughi, and F.L. Hepburn, 2006, “Millimeter-Wave Detection of Localized Anomalies in the Space Shuttle External Fuel Tank Insulating Foam,” IEEE Transactions on Instrumentation and Measurement, Vol. 55, No. 4, pp. 1250–1257.
Kharkovsky, S., R. Zoughi, and F.L. Hepburn, 2007, “High Resolution Millimeter Wave Imaging of Space Shuttle Fuel Tank Spray-On-Foam Insulation,” Materials Evaluation, Vol. 65, No. 12, pp. 1220–1229.
Krautkrämer, J., and H. Krautkrämer, 1990, Ultrasonic Testing of Materials, 4th edition, Springer-Verlag Berlin Heidelberg, Köln, Germany.
Lanza di Scalea, F., and R.E. Green, Jr., 2000, “A Hybrid Non-Contact Ultrasonic System for Sensing Bond Quality in Tow-Placed Thermoplastic Composites,” Journal of Composite Materials, Vol. 34, No. 21, pp. 1860–1880.
Mason, W.P., and H.J. McSkimin, 1947, “Attenuation and Scattering of High Frequency Sound Waves in Metals and Glasses,” Journal of the Acoustical Society of America, Vol. 19, No. 3, pp. 464–473.
Maynard, J. D., 1992, “The Use of Piezoelectric Film and Ultrasound Resonance to Determine the Complete Elastic Tensor in One Measurement,” Journal of the Acoustical Society of America, Vol. 91, No. 3, pp. 1754–1762.
Sherlock, R.A., and D.O. Edwards, 1970, “Oscillating Superleak Second Sound Transducers,” Review of Scientific Instruments, Vol. 41, No. 11, pp. 1603–1609.
Soumekh, M., 1992, “A System Model and Inversion for Synthetic Aperture Radar Imaging,” IEEE Transactions on Image Processing, Vol. 1, No. 1, pp. 64–76.
Sugasawa, S., 2002, “Time Difference Measurement of Ultrasonic Pulses Using Cross-Correlation Function between Analytic Signals,” Japanese Journal of Applied Physics, Vol. 41, Part 1, No. 5B, pp. 3299–3307.
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