抄録
The distributions of drying set in Sugi (Cryptomeria japonica D. Don) and Hinoki (Chamaecyparis obtusa Endl.) boxed-heart timbers without back-splitting dried by the high-temperature setting method (HTS method) are reported. The lengths of slices cut from dried timber were measurerd before and after recovery treatments (moistening or immersion in boiling water). By moisture and heat treatment, the dimension of each slice is restored to it's original one. Therefore, the differences in lengths of slices between before and after treatment denote recovered set. The residual stresses in boxed-heart timber dried by the HTS method were also measuerd by a modified slicing technique with putting in a stainless pin (∅=0.5mm).
Main results are shown below.
(1) Remarkable tension set (about 2.1%) developed in shells (slices No. 1 and 10).
(2) Hygro-recovery of drying set was observed only in the surface slices No. 1 and 10 and their values were about 0.6-0.8% (28-38% of total set).
(3) Hygrothermal recovery of drying set was observed in most of slices. The set recovery in slice No. 1 and 10 were big (aboult 1.3-1.5%), Which is equivaleht to 62-72% of total set.
(4) Boxed-heart square timbers without back-splitting dried by the HTS method were severely casehardened, that is, the shell of timber is stressed in compression and the core in tension.
