bonded connections is investigated. Various stress wave parameters, i.e., stress wave factors were used and correlated to the shear strength of the adhesive bonded connections. Stress wave factor measurements were obtained both before and after the wood beam samples were subjected to temperature and humidity conditioning to simulate aging or wear of the glueline. A number of stress wave factors in the time and frequency domain exhibited excellent correlation with the shear strength of the adhesive bond. In addition, the stress wave factor measurements belt)re and after conditioning correlated well with one another.

43646 Chern, EJ.; Djordjevic. B.B,; Abeam, J.S.; McNamara, D.K.; Desai, A. Ultrasonic evaluation of aluminum to aluminum adhesive bond durab i l i t y Nondestructive Testing and Evaluation for Manufacturing and Construction. Edited by H .LM. dos Reis. pp. 417-424. Hemisphere Publishing Corporation, (1990). ISBN 0-89116-926-1

In this paper, after reviewing the factors affecting the bonds in aluminum-to- aluminum (AI/AI) adhesive bond quality, we report 50-MHz acoustical microimaging results that qualitatively demonstrate the applicability of using high-frequency stress-waves for durability evaluation of AI/AI adhesive bonds.

43627 Cawley. P. Inspection of adhesive joints using ultrasonic spectroscopy Impact of Non-Destructive Testing, Proceedings of the 28th Annual British Conl~erence of Non-Destructive Testing, Sheffield (United Kingdom), 18-21 Sep. 1989. pp. 51-15. Edited by C. Brook and P.D. Hanstead. Pergamon Press, 1989.

The use of ultrasonic spectroscopy for the non-destructive determination of the cohesive properties of the adhesive layer in a joint is described, it has been shown that measurements of the through thickness natural frequencies of the joint obtained using ultrasonic spectroscopy can be used to calculate the modulus and thickness of the adhesive layer. The results reported here indicate that the modulus may be determined to an accuracy of +~o%, and the thickness may be found as accurately as it can be measured independently.

43425 Duverm~is, P.; Chatellier, J.Y. Non-destructive ultrasonic testing of bonded joints Establishment Technique de l 'Armement, Arcueil, (France), PB89- 225114/GAR, 70pp. (2 Feb. 1989). (In French, English abstract)

The first part of the document pre~nts results obtained through ultrasonic testing and tensile tests performed on some 100 specimens of bonded joints. The limitations of ultrasonic testing equipment and the prospects it offers are presented through the conclusions of research performed under the research assignment. The second part is a bibliographic search of a prospective nature. It follows the development of tests oriented toward fault location, and !ts object is to identify the parameters related to the ultrasonic wave that would make it possible to characte~'ize adhesion.

43389 Mm'lo. H.; Czarnecki, J.v.; Lauterborn, E. High frequency ultrasonic examination of carbon fibre composites and polymer-metal interfaces Materialprufung, Vol. 32, No. 4, pp. 106-109 (Apr. 1990) (In German, English abstract)

Carbon fibre reinforced composites and polymer-metal interfaces of adhesive joints and coatings are investigated by means of acoustic microscopy. The results presented, demonstrate the potential of this technique for non-destructive, high resolution subsurface imaging of delamination, debonding and interface degradiation. The necessity for high resolution digitizing of the echo amplitude is pointed out, by which means small defects and interface structures with only minor variations in reflectivity become detectable. A detailed discussion of acoustic microscopy in combination with image processing is given.

43175 Lethiecq, M. Signal treatment and data analysis methods applied to nondestructive control of adhesive bonded joints. (In French) Institut National des Sciences Appliquees de Lyon, Villeurbanne, (France), N89-22936/3/GAR. 175pp. (1989)

Adhesive bonding of a piezoelectric ceramic to an aluminium substrate was assessed. The methods tested include longitudinal and transversal ultrasonics and electric impedance measurement. The correlation between the nondestructive measure- ments and the destructive tests was performed by the principal components methods. The error rate in detecting defective elements is l0 percent. The transversal ultrasonics method is shown to be the best for quality control.

43124 Pilarski. A.; Rose, J.L.; Balasubramaniam. K.; Da-Le, J. Utilization of oblique incidence in acousto-ultrasonics Acousto-Ultrasonics, Theory and Application. Edited by J,C. Duke. Jr., pp. 78-9 I, Plenum Press, 353pp (1989). ISBN 0306430134

The acousto-ultmsonic test technique has proven itself as a very valuable nondestructive evaluation procedure. The technique, however, is severely limited by using norulal beam incidence of two transducers side by side. The current theoretical explanation of the wave propagation phenomena in ultrasonic NDE is limited. The purpose of this paper is to explore the full potential of the acousto-ultrasonie technique by way of including oblique incidence, and some theoretical explanation of wave propagation in the structure. By doing this, greater benefit of acousto-ultrasonic nondestructive evaluation can be realized. Several sample problems that could fit into the category of acoosto-ultrasonic evaluation are presented and outlined in the paper; the goal being to demonstrate the versatility of the acousto-ultrasonic technique.

43110 dos Reis. ft.L.M. Acousto-u l t rasonics : app l i ca t ions to wi re rope, wood f iber h a r d b o a r d , and adhesion Acousto-Ultrasonics, Theory and Application. Edited by J.C. Duke, Jr.. pp. 283-299, Plenum Press, 353pp (1989). 1SBN 0306430134

Applications of the Acousto-Ultrasonic Stress Wave Factor lEchnique (SWF) to the nondestructive evaluation/characterization of wire rope, wood fiber hardboard, and adhesion between rubber-like materials and steel subslrates are presented. It was observed that for each application the SWF technique has the potential of being used as a nondestructive testing tool. The SWF technique proved successful to monitor progressive damage in wire rope and wood fiber hardboard, and to monitor the strength of the bond between rubber layers and steel plates.

42867 Challis, R.[£.; AIper, 7". Ultrasonic propagation in thin adhesive layers Proceedings of Ultrasonics International 89, Madrid (Spain), 3-7 July 1989, pp. 1057-1062, Butterworth Scientific Ltd. ISBN 0408054182 (1989)

A novel wide bandwidth pulse transmission technique has been developed for the study of near plane wave ultrasound propagation in thin adhesive layers (0.l ram) set between aluminium or glass substrates. Very short acoustic pulses (2 ns to 20 ns) reverberate in the adhesive layer and propagate across substrate to the receiver. The signal received consists of a series of time resolvable multiple reverberations which are successively broader in the time domain due to attenuation and phase velocity dispersion in the bond. The changing shapes of successive reverberations are compared using conventional digital signal processing methods and yield absorption and velocity as functions of frequency, as well as models of material viscoelasticity, over wide bandwidths.

42848 Nagy, P.B.; Adler, 1,. Nondestructive evaluation of adhesive joints by guided waves Journal of Applied Physics, Vol, 66, No. 10, pp. 4658-4663 (15 Nov. 1989)

Guided waves in an adhesive layer between two adherend half-spaces are shown to be uniquely sensitive to most types of bond defects. A simple experimental technique based on ultrasonic transmission measurement is introduced to detect leaky guided modes in the interface layer. Experimental results for these dispersive guided modes are shown to be in good quantitative agreement with theoretical predictions. The suggested technique might find numerous applications in nondestructive evaluation of different bonds of layered structure such as adhesive and brazed joints.

42847 dos Reis, H.L.M. Non-destructive evaluation of adhesive bond strength in laminated wood beams British Journal of Non-Destructive Testing, Vol. 31, No. 12, pp. 675- 679 (Dec. 1989)

Acousto-Ultrasonic (AU) non-destructive evaluation of laminated wood beams has been conducted to evaluate the adhesive bond strength between two layers using the stress wave factor (SWF) measurement technique. Wood beam specimens with different levels of adhesive bond strength were manufactured and tested using the acousto-ultrasonic stress wave factor approach. The strength of the laminated wood beam specimens was then evaluated using the commonly umd destructive shear strength test method. It was observed that higher values of the SWF measurements correspond to higher values of the shear strength test data. Therefore, these results show that the acousto-ultrasonic approach has the potential of being used in quality assurance of the adhesive bond strength during the manufacturing process.

42658 Smith, A.C.; Yang. H. Ultrasonic study of adhesive bond quality a t a steel-to-rubber interface by using quadrature phase detection techniques Materials Evaluation, Vol. 47, No. 12, pp. 1396-1400 (Dec. 1989)

The quadrature phase detection technique was used to simultaneously monitor the phase and amplitude of a toneburst signal normally reflected from an adhesively bonded steel-to-rubber interface. The measured phase was found to show a positive shift for all bonded samples with respect to the disbonded state-the phase shift being larger for samples with weaker bonds, as manifested by smaller values of applied tensile loads at failure. A model calculation, which incorporates the concept of interracial strength into the usual problem of wave propagation in multilayered media. was used to deduce a bond- quality parameter from an experimentally measured phase shift. This bond-quality parameter was found to be correlated with the tensile strength of the adhesive bonds at failure loads.

42654 Dickstein, P.; Segal, Y.; Segal, E.; Sinclair, A.N. Statistical pattern recognition techniques: a sample problem of ultrasonic determination of interfacial weakness in adhesive joints Journal of Nondestructive Evaluation, Vol. 8, No. 1. pp. 27-35 (Mar. 1989)

A pattern recognition approach was applied to the analysis of ultrasonic echo signals from two classes of aluminum-to-aluminum adhesive bonds. The two classes differed in the surface preparation of the adherends prior to bonding, resulting in different interracial properties of the joints. Application of advanced signal processing and pattern recognition techniques enables the classification of the joints according to the surface preparation of the adherends, based on features extracted from the ultrasonic signals.

42584 Duke. J.C.; Henneke, E.G.; Kierman, M.T.; Grosskopf, P.P. Study of the stress wave factor technique for evaluation of composite materials Virginia Polytechnic Institute and State University Blacksburg (United States), N89-21256/7/GAR, 61pp. (Jan. 1989)

The acousto-ultrasonic approach for nondestructive evaluation provides a measure-

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