Skip to content
Licensed Unlicensed Requires Authentication Published by De Gruyter June 1, 2005

Nondestructive characterization of wood by monitoring of local elastic anisotropy and dynamic nonlinearity

Igor Solodov, Klaus Pfleiderer and Gerhard Busse
From the journal

Abstract

The results of non-contact measurements of local in-plane elastic anisotropy in wood by monitoring the flexural plate wave velocity as a function of azimuth angle of propagation are reported. The Focused Slanted Transmission of air-coupled ultrasound is used to generate and detect locally the flexural waves in wood as well as to measure their velocities. The analysis presented shows that for thin plates the flexural wave velocity can be readily used to evaluate the anisotropy of Young’s modulus. This conclusion is confirmed by measurements of the plate wave anisotropy factors for veneer laminae and cross-ply laminates of spruce and beech. The technique is sensitive enough to detect the anisotropy variation of earlywood caused by the incorporation of latewood areas in growth rings. A new approach based on dynamic nonlinearity of wood is developed and applied to acoustic imaging of wood structure and detecting of defects in wood. The hysteresis mechanism of the dynamic nonlinearity is shown to dominate in clear wood and to manifest in a primary generation of odd acoustic harmonics. Local maxima of the odd higher harmonic amplitudes in the LR- and LT-planes of softwood are observed in the earlywood area close to latewood/earlywood transition interface that indicates the lower stiffness and strength of wood in those areas. The higher-order even harmonics and subharmonics in the nonlinear vibration spectra of wood are mostly produced by “clapping” in defect areas. Measurements of local amplitudes of these modes are applied to nonlinear acoustic imaging of cracks, delaminations and knots in wood and wood composites.

:

Corresponding author. Institute for Polymer Testing and Polymer Science (IKP), Nondestructive Testing (ZFP), Stuttgart University, Pfaffenwaldring 32, 70569 Stuttgart, Germany. E-mail:

References

Achenbach, J.D. Wave Propagation in Elastic Solids. North-Holland Publishing Company, Amsterdam, 1973.Search in Google Scholar

Agarwal, B.D., Broutman, L.J. Analysis and Performance of Fiber Composites. John Wiley & Sons, Inc., New York, 1990.Search in Google Scholar

Bodig, J., Jayne, B.A. Mechanics of Wood and Wood Composites. Van Nostrand Reinhold Company, New York, 1982.Search in Google Scholar

Bucur, V. Acoustics of Wood. CRC Press, Boca Raton, 1995.Search in Google Scholar

Bucur, V. and Rasolofosaon, P.N.J. (1998) Dynamic elastic anisotropy and nonlinearity in wood and rock. Ultrasonics38:813–824.Search in Google Scholar

Bucur, V. Nondestructive Characterization and Imaging of Wood. Springer-Verlag, Berlin Heidelberg, 2003.Search in Google Scholar

Briggs, A. Acoustic Microscopy. Clarendon Press, Oxford, 1992.Search in Google Scholar

Cremer, L. (1947) Über die Analogie zwischen Einfallswinkel und Frequenzproblemen. Arch. Electr. Übertragung1: 28.Search in Google Scholar

Haberger, C.C., Mann, R.W., Baum, G.A. (1979) Ultrasonic plate waves in paper. Ultrasonics17:57–62.Search in Google Scholar

Hearmon, R.F.S. (1948) The elasticity of wood and plywood. Forest Products Res. Spec. Report. No. 7, His Majesty’s Stationery Office, London.Search in Google Scholar

Luukkala, M., Heikkili, P., Surakka, J. (1971) Plate wave resonance – a contactless method. Ultrasonics9:201–208.Search in Google Scholar

Solodov, I., Krohn, N., Busse, G. (2002) CAN: an example of non-classical acoustic nonlinearity in solids. Ultrasonics40:621–625.Search in Google Scholar

Solodov, I., Pfleiderer, K., Gerhard, H., Predak, S., Busse, G. (2004) Slanted transmission mode of air-coupled ultrasound: new opportunities in NDT and material characterisation. In: Emerging Technologies in Non Destructive Testing. Eds. Van Hemelrijck, Anastasopoulos, Melanitis. Swets & Zeitlinger, Lisse. pp. 107–112.Search in Google Scholar

Zheng, Y., Maev, R., Solodov, I. (1999) Nonlinear acoustic applications for material characterization: A review. Can. J. Phys.77:927–967.Search in Google Scholar

Published Online: 2005-06-01
Published in Print: 2004-08-01

© Walter de Gruyter