ULTRASONIC VELOCITY AND MOISTURE-CONTENT IN WOOD .2. ULTRASONIC VELOCITY AND AVERAGE MOISTURE-CONTENT IN WOOD DURING DESORPTION(1) - MOISTURE-CONTENT BELOW THE FIBER SATURATION POINT

The relationships between ultrasonic velocity, in the radial and in th e longitudinal directions, and the average moisture content in wood du ring desorption from the vapor-saturated condition, were examined. Thi s included ultrasonic velocity in wood with and without moisture gradi ents in the moisture range below the fiber saturation point. Six speci es were used, and their dimensions for measurements in the radial dire ction differed from those in the longitudinal direction. All faces exc ept the measuring faces of specimen were coated with parafilm so that moisture-evaporation took place from one direction in a specimen. Alth ough the values of ultrasonic velocity were influenced by species and anatomical directions, the patterns of ultrasonic velocity versus aver age moisture content curves during desorption almost were independent of the species in the radial and in the longitudinal directions. When the relative ultrasonic velocity, ultrasonic velocity at 0% moisture c ontent, was taken as 100, that of each species was represented by one equation, and it was possible to estimate the ultrasonic velocity vers us the average moisture content curves of a species when the ultrasoni c velocity was known for any moisture content below the fiber saturati on point. The ultrasonic velocity in wood was influenced little by the moisture gradients in the direction of the measurement of ultrasonic velocity.