In the foregoing studies in this series, we discussed the behavior of the shrinkage under tensile load (1), the effect of tensile load on the deformation and creep failure (2), and the influence of temperature on some behaviors of wood during drying under tensile load (3) (4).
It was shown previously that a remarkable creep occured at some period of drying, and this was assumed to be due to the plastic nature of wood, derived from the non-equilibrium of moisture, and the creep was influenced more markedly at higher temperature. In the present paper is discussed the tensile creep of the specimen with a thickness different from the previously one (1). There are used the specimen of radial plane of sliced veneer of SUGI (Cryptomeria japonica D. DON.) (150 μ thickness) and SIOJI (Fraxinus commemoralis KOIDZ.) (300 μ thickness). The experimental temperature were 40゜, 60゜ and 80℃. The shape and dimension of the specimen are shown in Fig. 1, and the method of experiment followed that discribed in the previous paper (1). Test specimens were dried from the initial moisture content of about 290% to about 5%.
Experimental results are summerized as follows :
The shrinkages during drying at 40゜, 60゜ and 80℃. are shown in Fig.2, 4 and 5, and the tensile creeps during drying under tensile load in Fig. 6 and 7. The shrinkage curves and tensile creep curves during drying for softwood are in similar behavior as in previous reports (1) (4), but, though the shrinkage curves during drying for hard wood are similar behavior to softwood, for the tensile creep curves of hardwood, the results were rather differed with the behavior of softwood in the period after about 9 minutes since drying was started. And so, for hardwood, it appears to examine the relation between the variation of shrinkage or tensile creep and the structure of wood during drying under tensile load in future.