ULTRASONIC VELOCITY AND MOISTURE-CONTENT IN WOOD .3. ULTRASONIC VELOCITY AND AVERAGE MOISTURE-CONTENT IN WOOD DURING DESORPTION .2. DURING DESORPTION FROM A WATER-SATURATED CONDITION ENGLISH, JAPANESE

The relationship between ultrasonic velocity in the radial and longitu dinal directions and the average moisture content in wood during desor ption from a water-saturated condition was examined. The species used were sugi (Cryptomeria japonica D. Don), hinoki (Chamaecyparis obtusa Endl.), beisugi (Thuja plicata D. Don), agathis (Agathis sp,),buna (Fa gus crenata Blume), makanba (Betula maximowicziana Regel) and shioji ( Fraxinus commemoralis Koidz.) and their dimensions for measurements in the radial directions differed from that in the longitudinal directio ns. All faces except the measuring faces of specimens were coated with parafilm so that moisture evaporation took place from one direction. During desorption from water-saturated conditions, the patterns of ult rasonic velocities versus average moisture content in the radial and l ongitudinal directions varied very much with species, and they could b e divided into three groups. In the first group in the radial directio ns, ultrasonic velocities decreased from water-saturations to about av erage moisture contents of 40%; after that, they increased quickly as average moisture contents decreased. The species of each group did not correspond in the radial and longitudinal directions. The pattern of ultrasonic velocity versus average moisture content on a graph in the radial direction during desorption from water-saturated conditions can be explained by the law of composites for their moisture distribution .