SOUND-VELOCITY OF WOOD WITH LAYER CONSTRU CTION ENGLISH, JAPANESE

When the elastic modulus of wood, composed of earlywood and latewood w ith different specific gravities and elastic moduli, is estimated non- destructively from sound velocity by the ultrasonic propagation method , it is important to make clear the effect of the layer structure of t he earlywood and latewood on the sound velocity. The sound velocities of specimens laminated parallel or in series to wood with different so und velocities (three structural direction; longitudinal, tangential, and radial directions and species) were determined. The species used w ere sugi (Cryptomeria japonica D. Don) and karamatsu (Larix leptolepis Gord) for softwood, kumashide (Carpinus japonica Blume) for diffuse-p orous hardwood, yachidamo (Fraxinus mandshurica Rupr. var. japonica Ma xim.), and mizunara (Quercus mangolica Fisch var, grosseserrata Rehd. and Wils.) for ring-porous hardwood. Results were obtained as follows: (1) The actual propagation time of specimens in series was equal to t he sum of the propagation time computed for each element. (2) When the actual sound velocity was compared those computed from Equations (3) or (8) in series, both almost coincided, but it were influenced by the length ratio of each element in part. (3) The actual sound velocities of specimens in parallel remarkably were dependent on the element wit h the high level of sound velocity. (4) The actual sound velocity of a specimen in parallel was decreased with the decrement of the width ra tio of the element with a large sound velocity, as was the tendency of sound velocity computed by Equation (17). The degree of decrement in actual sound velocity was less than that of the computed one. (5) Gene rally it was expected that the sound velocity in the radial direction was applied to the estimation of elastic moduli in different structura l directions by means of sound velocity (ultrasonic propagation method ).