ATTENUATION OF ULTRASONIC-WAVES IN WOOD

Clarification of the effects of wood characteristics on the attenuation of ultrasonic waves is required in both acousto-ultrasonics (AU) and acoustic emission (AE) techniques to determine the effects of them on AU/AE parameters. The AU signal source was made by the injection of a pulse with a transmitting transducer (150 kHz), and the contour maps of the maximum amplitude of the AU signal detected by a receiving transducer (150 kHz) were made on the surfaces of lumber of Japanese larch (Larix leptolepis Gord.) and red lauan (Shorea spp.). The effects of microfibril angles and densities on longitudinal AU wave propagation also was examined by radially scanning a pair of transducers on a disc of Japanese larch. The contour map showed that AU waves propagat along the grain, and the propagation is dominated by the latewood. The attenuation of AU waves was more significant for red lauan which is without latewood, than was Japanese larch. The longitudinal attenuation of ultrasonic waves was affected mainly by the microfibrill angles.