Experimental and Numerical Methods for Detection of Voids in Wood Poles Using Ultrasonic Testing
Publication: Journal of Materials in Civil Engineering
Volume 25, Issue 6
Abstract
Utility wood poles are extensively used to support electrical-transmission and distribution lines in North America. Wood poles are exposed to extreme weather conditions, making them vulnerable to internal deterioration resulting in loss of pole strength, which can compromise the reliability of energy supply to customers. Ultrasonic testing is a nondestructive method that has been used for evaluation of the internal condition of in-service wood poles. However, the current assessment criterion is mostly based only on the first arrival of compression waves. This paper presents experimental and numerical methods for the detection of voids in wood poles using ultrasonic waves; the wood is considered as an orthotropic material. This investigation involves ultrasonic testing of a red-pine pole without and with a void. Changes in both compression wave velocity and wave attenuation are used to identify the presence of a void. An orthotropic finite-element model, calibrated with experimental results, is used to study the propagation of ultrasonic waves in a cross section of red-pine poles. Experimental and numerical results show that for a void–pole diameter ratio of and frequency of 50 kHz (), the wave velocity across the pole decreases an average of 20%, whereas the wave is attenuated by a factor of 10. Thus, the consideration of wave attenuation in addition to wave velocity is critical to improve the reliability of current methodologies. The compression wavefront shows a triangular shape before reaching the pith of the wood pole, after which it shows a circular shape, as in the case of an isotropic material. In addition, the surface wave shows displacements mostly in the radial direction instead of the typical retrograde ellipse in an isotropic medium.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The authors would like express their gratitude to the Natural Sciences and Engineering Research Council of Canada (NSERC), University Network of Excellence in Nuclear Engineering (UNENE), OCE–Centre for Earth and Environmental Technologies, and Dillon Consulting/Waterloo Geophysics Inc. for the funding provided for this research.
References
ANSYS 11.0 [Computer software]. ANSYS, Canonsburg, PA.
Au, M., Moghaddam, A. N., and Smith, J. (2002). “Material characterization with ultrasonic waves. Nondestructive testing of wood beams.” Technical Rep., Univ. of Waterloo Dept. of Civil Engineering, Waterloo, ON.
Braun, S., and Hammond, K. J. (1986). “Mechanical Signature Analysis: Theory and applications.” Chapter 5, Parametric methods, S. Braun, ed., Academic Press, Waltham, MA, 103–138.
Clough, R. W., and Penzien, J. (2003). Dynamics of structures, 3rd Ed., Computers and Structures, Berkeley, CA.
Emerson, R., Pollock, D., McLean, D., Fridley, K., Pellerin, R., and Ross, R. (2002). “Ultrasonic inspection of large bridge timbers.” For. Prod. J., 52(9), 88–95.
Green, D. W., Winandy, J. E., and Kretschmann, D. E. (1999). “Mechanical properties of wood.” Chapter 4, Wood handbook: Wood as an engineering material (General Technical Rep. FPL GTR 113), USDA Forest Service, Forest Products Laboratory, Madison, WI, 1–45.
Halabe, U. B., Bidigalu, G. M., GangaRao, H. V., and Ross, R. J. (1997). “Non-destructive evaluation of green wood using stress wave and transverse vibration techniques.” Mater. Eval., 55(9), 1013–1018.
Hasenstab, A., Hillemeier, B., and Krause, M. (2005). “Defect localisation in wood with low frequency ultrasonic echo technique.” In 14 Int. Symp. on Nondestructive Testing of Wood, Hannover, Germany, 329–336.
Maurer, H. R., et al. (2005). “Application of nonlinear acoustic tomographic for non-destructive testing of trees.” Proc., 14th Int. Symp. on Nondestructive Testing of Wood, Shaker, Herzogenrath, Germany, 337–349.
Pandey, M. D., Ho, V., Bedi, S., and Woodward, S. (2005). “Development of a condition assessment model for transmission line in-service wood crossarms.” Can. J. Civ. Eng., 32(3), 480–489.
Payton, R. G. (2003). “Wave fronts in wood.” Q. J. Mech. Appl. Math., 56(4), 527–546.
Ross, R. J., and Hunt, M. O. (2000). “Stress wave timing nondestructive evaluation tools for inspecting historic structures: A guide for use and interpretation.” Technical Rep., USDA, Washington, DC.
Ross, R. J., Wang, X., and Brashaw, B. (2005). “Detecting decay in wood components.” Chapter 5, Inspection and monitoring techniques for bridges and civil structures, G. Fu, ed., Woodhead, Cambridge, UK, 100–114.
Sandoz, J. L. (1996). “Ultrasonics solid wood evaluation in industrial applications.” In 10th Int. Symp. on Nondestructive Testing of Wood, Lausanne, Switzerland, 147–154.
Schubert, S., Gsell, D., Niemz, P., and Dual, J. (2005). “Numerical simulation of elastic wave propagation in the radial-tangential plane of wooden trunks with and without fungal decay.” Proc., 3rd Int. Workshop, NDT in Progress, Univ. of Technology, Prague, Czech Republic.
Tallavo, F. (2009). “New methodology for the assessment of decayed utility wood poles using ultrasonic testing.” Ph.D. thesis, Univ. of Waterloo, Waterloo, ON.
Tallavo, F., Cascante, G., and Pandey, M. D. (2009). “New methodology for source characterization in pulse velocity testing.” Geotech. Test. J., 32(6), 537–552.
Tiita, M. E., Beall, F. C., and Biernacki, J. M. (2001). “Classification study for using acoustic-ultrasonics to detect internal decay in glulam beams.” Wood Sci. Technol., 35, 85–96.
USDA. (1996). “Pole inspection and maintenance.”, Washington, DC.
Vector. (2004). Electricity–asset management plan, Auckland, New Zealand.
Information & Authors
Information
Published In
Journal of Materials in Civil Engineering
Volume 25 • Issue 6 • June 2013
Pages: 772 - 780
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Feb 10, 2012
Accepted: Jul 9, 2012
Published online: May 15, 2013
Published in print: Jun 1, 2013
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.