Journal of the Korean Wood Science and Technology

The Korean Society of Wood Science & Technology (한국목재공학회)
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The Characteristics of Ultrasonic Wave Transmitted Through Drying Wood

  • Kang, Ho-Yang (College of Agriculture and Life Science, Chungnam National University)
  • Received : 2010.05.17
  • Accepted : 2010.10.13
  • Published : 2011.03.25
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Abstract

The possibility of using the properties of an ultrasonic wave as a means for monitoring the moisture content of a board during drying was investigated. The ultrasonic wave signals are influenced by moisture content and other factors such as temperature, moisture gradient and coupling area. The effect of temperature was examined by measuring the transit times, amplitudes and velocities of ultrasonic waves transmitted through air, a metal bar and a board at various temperatures. The effect of a moisture gradient was studied using a model specimen composing five wood pieces of various moisture contents. The velocity and amplitude of the ultrasonic waves transmitted through air increase with temperature, while those through a metal bar and a board decrease. It was confirmed that the temperature effect is partially attributed to the change of transducer's properties. The effect of a moisture gradient on the velocity of an ultrasonic wave varies with the average moisture content of a board. As the dimension of the end face of a board increases the velocity of an ultrasonic wave increases and low frequency components more dominates than high frequency components. The transit times of ultrasonic waves transmitted through a board during kiln drying reflect the temperature steps in the drying schedule and the transducer temperatures.

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References

  1. Beall, F. C. 2002. Overview of the use of ultrasonic technologies in research on wood properties. Wood Science and Technology 36(3): 197-212 https://doi.org/10.1007/s00226-002-0138-4
  2. Booker, R. E., J. Froneberg, and F. Collins. 1996. Variation of sound velocity and dynamic Young's modulus with moisture content in the three principal directions. Proceedings 10th International Symposium on Non-Destructive Testing of Wood, Lausanne, Switzerland, 26-28 August 1996: 279 -295.
  3. James, W. L. 1961. Internal friction and speed of sound in Douglas-fir. Forest Products Journal 11(9): 383-390.
  4. James, W. L., R. S. Boone, and W. L. Galligan. 1982. Using speed of sound in wood to monitor drying in a kiln. Forest Products Journal 32(9): 27-34.
  5. Kang, H. and R. E. Booker. 2002. Variation of stress wave velocity with MC and temperature. Wood Science and Technology 36(1): 41-54. https://doi.org/10.1007/s00226-001-0129-x
  6. Mishiro, A. 1995. Effects ultrasonic velocity in wood and its moisture content I. Effects of moisture gradients on ultrasonic velocity in wood. Mokuzai Gakkaishi 41(12): 1086-1092.
  7. Sakai, H., A. Minamisawa, and K. Takagi. 1990. Effect of moisture content on ultrasonic velocity and attenuation in woods. Ultrasonics 28 November: 382-385. https://doi.org/10.1016/0041-624X(90)90060-2
  8. Sandoz, J. L. 1993. Moisture content and temperature effect on ultrasound timber grading. Wood Science and Technology 27: 373-380.
  9. Simpson, W. T. and X. Wang. 2001. Relationship between longitudinal stress wave transit time and moisture content of lumber during kiln-drying. Forest Products Journal 51(10): 51-54.
  10. van Dyk, H. and R. W. Rice. 2006. Ultrasonic wave velocity as a moisture indicator in frozen and unfrozen lumber. Forest Products Journal 55(6): 68-72.
  11. Wang, S. Y., C. M. Chiu, and C. J. Lin. 2002. Variations in ultrasonic wave velocity and dynamic young's modulus with moisture content for Taiwania plantation lumber. Wood and Fiber Science 34(3): 370-381.
  12. Weast, R. C. 1985. CRC Handbook of Chemistry and Physics 66th Ed. (F-106 p). CRC Press. Boca Ratan, Florida, USA.