抄録
Moisture gradient during drying of Sugi lumber with core brings about large tensile strain in the tangential direction. Since this strain could be reduced with smaller moisture gradient in the radial direction, Sugi disk pieces with core were pierced along the fiber direction (diameter: 100mm, thickness: 20mm, diameter of hollow: 40mm) and dried under the condition of 80°C and 40%RH. The relationship between the moisture gradient and the strain was studied.
The results obtained were as follows:
(1) The disk pierced along the fiber direction could be dried rapidly and without split because of large moisture gradient between the center and the outside or surface of hollow. But in the case of sealed hollow disk specimen, the drying time became long and large split occurred.
(2) Shrinkage in the hollow diameter was greater than that in the overall diameter of the disk and still greater than the tangential shrinkage measured according to the Japanese Industrial Standards.
(3) The tangential strain at the hollow surface remained compressive in the final stage because hoop stress acted on the disk.
(4) The tensile strain on the outside was reduced by hoop stress.
