Application of Ultrasonic Scanning in the Wood Products Industry
Tomoaki SOMA Grad Schvol of Agr. & Agr. Life Sci., Univ. of Tokyo, JAPAN Satoshi SHIDA Grad School of Agr. & Agr. Life Sci., Univ. of Tokyo, JAPAN Takanori ARIMA Grad Schovl of Agr. & Agr. Life Sci., Univ. of Tokyo, JAPAN
ABSTRACT
Ultrasonic method gives us the internal information of materials. The measurement of ultrasonic velocity has been used as a valuable and important method, because it is non-destructive method and simple to use. This paper focused on relationship between moisture content and ultrasonic velocity in wood. Ultrasonic velocity slightly responds to moisture content change in region of free water. This fact means that high moisture content such as in region of free water is not always estimated by ultrasonic wave. Specimens were frozen to detect high moisture content by ultrasonic wave. There was expectation that the route of ultrasonic waves was changed by the freezing-treatment. It was examined that free-water changed from liquid to solid in wood affected on ultrasonic velocity. As a result, freezing-treatment gained ultrasonic velocity with high moisture content specimens in longitudinal (L), radial (R) and tangential (T) directions. The ultrasonic velocities of air-dried specimen were about 2.3 and 1.9 km/s in R and T directions respectively. With increasing moisture content in R and T directions, ultrasonic velocity of non-treated specimen was slightly decreased and getting on for the value of liquid water (1.50 km/s), on the other hand, the value of freezing-treated was dramatically increased and approximated to the value of solid (3.23 km/s). Consequently, the absolute value of inclination from air-dried state to high moisture state in freezing-treated specimens was higher than in non-treated specimens. Therefore, freezing-treatment was extremely effective to evaluate high moisture contents. Furthermore, to detect moisture gradients a simple equation was proposed, which divided transverse moisture gradients into two parts: air-dried part and water-saturated part. It gave the ratio of air-dried part to water-saturated part as length. The values tended to be close to experimented one.
Publication Source: Proceedings of the 12th International Symposium on Nondestructive Testing of Wood University of Western Hungary, Sopron, 13-15 September 2000, ISBN 963 7180 88 5 Publisher: University of Western Hungary, H 9400 Sopron, P.O.Box 132, FAX: +36 99 311 103
